Release v3.1.2 (#2885)

- bump version
- update release notes

.github/ISSUE_TEMPLATE/bug_report.yml

@@ -6,7 +6,7 @@ body:
 - type: markdown
   attributes:
     value: |
-      If you have a question please post it on channel [#patroni](https://postgresteam.slack.com/archives/C9XPYG92A) in the [PostgreSQL Slack](https://join.slack.com/t/postgresteam/shared_invite/zt-1qj14i9sj-E9WqIFlvcOiHsEk2yFEMjA).
+      If you have a question please post it on channel [#patroni](https://postgresteam.slack.com/archives/C9XPYG92A) in the [PostgreSQL Slack](https://pgtreats.info/slack-invite).
       Before reporting a bug please make sure to **reproduce it with the latest Patroni version**!
       Please fill the form below and provide as much information as possible.
       Not doing so may result in your bug not being addressed in a timely manner.

.github/ISSUE_TEMPLATE/config.yml

@@ -1,5 +1,5 @@
 blank_issues_enabled: false
 contact_links:
 - name: Question
-  url: https://join.slack.com/t/postgresteam/shared_invite/zt-1qj14i9sj-E9WqIFlvcOiHsEk2yFEMjA
+  url: https://pgtreats.info/slack-invite
   about: "Please ask questions on channel #patroni in the PostgreSQL Slack"

.github/workflows/install_deps.py

@@ -19,7 +19,7 @@ def install_requirements(what):
     requirements = ['mock>=2.0.0', 'flake8', 'pytest', 'pytest-cov'] if what == 'all' else ['behave']
     requirements += ['coverage']
     # try to split tests between psycopg2 and psycopg3
-    requirements += ['psycopg[binary]'] if sys.version_info > (3, 7, 0) and\
+    requirements += ['psycopg[binary]'] if sys.version_info >= (3, 8, 0) and\
         (sys.platform != 'darwin' or what == 'etcd3') else ['psycopg2-binary']
     for r in read('requirements.txt').split('\n'):
         r = r.strip()
@@ -45,8 +45,8 @@ def install_packages(what):
     packages['exhibitor'] = packages['zookeeper']
     packages = packages.get(what, [])
     ver = versions.get(what)
-    if float(ver) >= 15:
-        packages += ['postgresql-{0}-citus-11.2'.format(ver)]
+    if float(ver) == 15:
+        packages += ['postgresql-{0}-citus-12.0'.format(ver)]
     subprocess.call(['sudo', 'apt-get', 'update', '-y'])
     return subprocess.call(['sudo', 'apt-get', 'install', '-y', 'postgresql-' + ver, 'expect-dev'] + packages)
 
@@ -85,8 +85,8 @@ def unzip_all(archive):
 
 
 def chmod_755(name):
-    os.chmod(name, stat.S_IRUSR | stat.S_IWUSR | stat.S_IXUSR |
-             stat.S_IRGRP | stat.S_IXGRP | stat.S_IROTH | stat.S_IXOTH)
+    os.chmod(name, stat.S_IRUSR | stat.S_IWUSR | stat.S_IXUSR
+             | stat.S_IRGRP | stat.S_IXGRP | stat.S_IROTH | stat.S_IXOTH)
 
 
 def unpack(archive, name):

.github/workflows/mapping.py

@@ -1 +1 @@
-versions = {'etcd': '9.6', 'etcd3': '14', 'consul': '13', 'exhibitor': '12', 'raft': '11', 'kubernetes': '15'}
+versions = {'etcd': '9.6', 'etcd3': '16', 'consul': '13', 'exhibitor': '12', 'raft': '11', 'kubernetes': '15'}

.github/workflows/tests.yaml

@@ -5,6 +5,7 @@ on:
   push:
     branches:
     - master
+    - 'REL_[0-9]+_[0-9]+'
 
 env:
   CODACY_PROJECT_TOKEN: ${{ secrets.CODACY_PROJECT_TOKEN }}
@@ -116,8 +117,8 @@ jobs:
         sudo apt-get install -y wget ca-certificates gnupg debian-archive-keyring apt-transport-https
         sudo sh -c 'echo "deb http://apt.postgresql.org/pub/repos/apt $(lsb_release -cs)-pgdg main" > /etc/apt/sources.list.d/pgdg.list'
         sudo sh -c 'wget -qO - https://www.postgresql.org/media/keys/ACCC4CF8.asc | gpg --dearmor > /etc/apt/trusted.gpg.d/apt.postgresql.org.gpg'
-        sudo sh -c 'echo "deb [signed-by=/etc/apt/trusted.gpg.d/citusdata_community.gpg] https://repos.citusdata.com/community/ubuntu/ $(lsb_release -cs) main" > /etc/apt/sources.list.d/citusdata_community.list'
-        sudo sh -c 'wget -qO - https://repos.citusdata.com/community/gpgkey | gpg --dearmor > /etc/apt/trusted.gpg.d/citusdata_community.gpg'
+        sudo sh -c 'echo "deb [signed-by=/etc/apt/trusted.gpg.d/citusdata_community.gpg] https://packagecloud.io/citusdata/community/ubuntu/ $(lsb_release -cs) main" > /etc/apt/sources.list.d/citusdata_community.list'
+        sudo sh -c 'wget -qO - https://packagecloud.io/citusdata/community/gpgkey | gpg --dearmor > /etc/apt/trusted.gpg.d/citusdata_community.gpg'
       if: matrix.os == 'ubuntu'
     - name: Install dependencies
       run: python .github/workflows/install_deps.py
@@ -157,3 +158,44 @@ jobs:
     steps:
     - run: bash <(curl -Ls https://coverage.codacy.com/get.sh) final
       if: ${{ env.SECRETS_AVAILABLE == 'true' }}
+
+  pyright:
+    runs-on: ubuntu-latest
+    steps:
+    - uses: actions/checkout@v3
+
+    - name: Set up Python 3.11
+      uses: actions/setup-python@v4
+      with:
+        python-version: 3.11
+
+    - name: Install dependencies
+      run: python -m pip install -r requirements.txt psycopg2-binary psycopg
+
+    - uses: jakebailey/pyright-action@v1
+      with:
+        version: 1.1.326
+
+  docs:
+    runs-on: ubuntu-latest
+    steps:
+    - uses: actions/checkout@v3
+
+    - name: Set up Python 3.11
+      uses: actions/setup-python@v4
+      with:
+        python-version: 3.11
+        cache: pip
+
+    - name: Install dependencies
+      run: pip install tox
+
+    - name: Install package dependencies
+      run: |
+        sudo apt update \
+        && sudo apt install -y \
+            latexmk texlive-latex-extra tex-gyre \
+            --no-install-recommends
+
+    - name: Generate documentation
+      run: tox -m docs

.gitignore

@@ -51,9 +51,16 @@ scm-source.json
 docs/build/
 docs/source/_static/
 docs/source/_templates/
+docs/modules/
 
 # Pycharm IDE
 .idea/
 
 #VSCode IDE
 .vscode/
+
+# Virtual environment
+venv*/
+
+# Default test data directory
+data/

.readthedocs.yaml

@@ -0,0 +1,26 @@
+# .readthedocs.yaml
+# Read the Docs configuration file
+# See https://docs.readthedocs.io/en/stable/config-file/v2.html for details
+
+# Required
+version: 2
+
+# Set the version of Python and other tools you might need
+build:
+  os: ubuntu-22.04
+  tools:
+    python: "3.11"
+
+# Build documentation in the docs/ directory with Sphinx
+sphinx:
+  configuration: docs/conf.py
+
+formats:
+  - epub
+  - pdf
+  - htmlzip
+
+python:
+  install:
+    - requirements: requirements.docs.txt
+    - requirements: requirements.txt

Dockerfile

@@ -25,8 +25,7 @@ RUN set -ex \
             | grep -Ev '^python3-(sphinx|etcd|consul|kazoo|kubernetes)' \
             | xargs apt-get install -y vim curl less jq locales haproxy sudo \
                             python3-etcd python3-kazoo python3-pip busybox \
-                            net-tools iputils-ping --fix-missing \
-    && pip3 install dumb-init \
+                            net-tools iputils-ping dumb-init --fix-missing \
 \
     # Cleanup all locales but en_US.UTF-8
     && find /usr/share/i18n/charmaps/ -type f ! -name UTF-8.gz -delete \
@@ -53,14 +52,26 @@ RUN set -ex \
     && curl -sL "https://github.com/coreos/etcd/releases/download/v$ETCDVERSION/etcd-v$ETCDVERSION-linux-$(dpkg --print-architecture).tar.gz" \
             | tar xz -C /usr/local/bin --strip=1 --wildcards --no-anchored etcd etcdctl \
 \
-    # Download confd
-    && curl -sL "https://github.com/kelseyhightower/confd/releases/download/v$CONFDVERSION/confd-$CONFDVERSION-linux-$(dpkg --print-architecture)" \
-            > /usr/local/bin/confd && chmod +x /usr/local/bin/confd \
+    && if [ $(dpkg --print-architecture) = 'arm64' ]; then \
+        # Build confd
+        apt-get install -y git make \
+        && curl -sL https://go.dev/dl/go1.20.4.linux-arm64.tar.gz | tar xz -C /usr/local go \
+        && export GOROOT=/usr/local/go && export PATH=$PATH:$GOROOT/bin \
+        && git clone --recurse-submodules https://github.com/kelseyhightower/confd.git \
+        && make -C confd \
+        && cp confd/bin/confd /usr/local/bin/confd \
+        && rm -rf /confd /usr/local/go; \
+    else \
+        # Download confd
+        curl -sL "https://github.com/kelseyhightower/confd/releases/download/v$CONFDVERSION/confd-$CONFDVERSION-linux-$(dpkg --print-architecture)" \
+            > /usr/local/bin/confd && chmod +x /usr/local/bin/confd; \
+    fi \
 \
     # Clean up all useless packages and some files
     && apt-get purge -y --allow-remove-essential python3-pip gzip bzip2 util-linux e2fsprogs \
                 libmagic1 bsdmainutils login ncurses-bin libmagic-mgc e2fslibs bsdutils \
-                exim4-config gnupg-agent dirmngr libpython2.7-stdlib libpython2.7-minimal \
+                exim4-config gnupg-agent dirmngr \
+                git make \
     && apt-get autoremove -y \
     && apt-get clean -y \
     && rm -rf /var/lib/apt/lists/* \
@@ -143,14 +154,15 @@ WORKDIR $PGHOME
 
 RUN sed -i 's/env python/&3/' /patroni*.py \
     # "fix" patroni configs
-    && sed -i 's/^\(  connect_address:\|  - host\)/#&/' postgres?.yml \
     && sed -i 's/^  listen: 127.0.0.1/  listen: 0.0.0.0/' postgres?.yml \
     && sed -i "s|^\(  data_dir: \).*|\1$PGDATA|" postgres?.yml \
     && sed -i "s|^#\(  bin_dir: \).*|\1$PGBIN|" postgres?.yml \
     && sed -i 's/^  - encoding: UTF8/  - locale: en_US.UTF-8\n&/' postgres?.yml \
-    && sed -i 's/^\(scope\|name\|etcd\|  host\|  authentication\|  pg_hba\|  parameters\):/#&/' postgres?.yml \
+    && sed -i 's/^\(scope\|name\|etcd\|  host\|  authentication\|  connect_address\|  parameters\):/#&/' postgres?.yml \
     && sed -i 's/^    \(replication\|superuser\|rewind\|unix_socket_directories\|\(\(  \)\{0,1\}\(username\|password\)\)\):/#&/' postgres?.yml \
-    && sed -i 's/^      parameters:/      pg_hba:\n      - local all all trust\n      - host replication all all md5\n      - host all all all md5\n&\n        max_connections: 100/'  postgres?.yml \
+    && sed -i 's/^      parameters:/&\n        max_connections: 100/'  postgres?.yml \
+    && sed -i 's/^      pg_hba:/&\n      - local all all trust/' postgres?.yml \
+    && sed -i 's/^\(.*\) \(.*\) md5/\1 all md5/' postgres?.yml \
     && if [ "$COMPRESS" = "true" ]; then chmod u+s /usr/bin/sudo; fi \
     && chmod +s /bin/ping \
     && chown -R postgres:postgres "$PGHOME" /run /etc/haproxy

Dockerfile.citus

@@ -20,15 +20,28 @@ RUN set -ex \
     && export DEBIAN_FRONTEND=noninteractive \
     && echo 'APT::Install-Recommends "0";\nAPT::Install-Suggests "0";' > /etc/apt/apt.conf.d/01norecommend \
     && apt-get update -y \
-    # postgres:10 is based on debian, which has the patroni package. We will install all required dependencies
+    # postgres:PG_MAJOR is based on debian, which has the patroni package. We will install all required dependencies
     && apt-cache depends patroni | sed -n -e 's/.*Depends: \(python3-.\+\)$/\1/p' \
             | grep -Ev '^python3-(sphinx|etcd|consul|kazoo|kubernetes)' \
             | xargs apt-get install -y vim curl less jq locales haproxy sudo \
                             python3-etcd python3-kazoo python3-pip busybox \
-                            net-tools iputils-ping --fix-missing \
-    && curl https://install.citusdata.com/community/deb.sh | bash \
-    && apt-get -y install postgresql-$PG_MAJOR-citus-11.2 \
-    && pip3 install dumb-init \
+                            net-tools iputils-ping lsb-release dumb-init --fix-missing \
+    && if [ $(dpkg --print-architecture) = 'arm64' ]; then \
+        apt-get install -y postgresql-server-dev-$PG_MAJOR \
+                           git gcc make autoconf \
+                           libc6-dev flex libcurl4-gnutls-dev \
+                           libicu-dev libkrb5-dev liblz4-dev \
+                           libpam0g-dev libreadline-dev libselinux1-dev\
+                           libssl-dev libxslt1-dev libzstd-dev uuid-dev \
+        && git clone -b "main" https://github.com/citusdata/citus.git \
+        && MAKEFLAGS="-j $(grep -c ^processor /proc/cpuinfo)" \
+        && cd citus && ./configure && make install && cd ../ && rm -rf /citus; \
+    else \
+        echo "deb [signed-by=/etc/apt/trusted.gpg.d/citusdata_community.gpg] https://packagecloud.io/citusdata/community/debian/ $(lsb_release -cs) main" > /etc/apt/sources.list.d/citusdata_community.list \
+        && curl -sL https://packagecloud.io/citusdata/community/gpgkey | gpg --dearmor > /etc/apt/trusted.gpg.d/citusdata_community.gpg \
+        && apt-get update -y \
+        && apt-get -y install postgresql-$PG_MAJOR-citus-11.3; \
+    fi \
 \
     # Cleanup all locales but en_US.UTF-8
     && find /usr/share/i18n/charmaps/ -type f ! -name UTF-8.gz -delete \
@@ -55,16 +68,29 @@ RUN set -ex \
     && curl -sL https://github.com/coreos/etcd/releases/download/v${ETCDVERSION}/etcd-v${ETCDVERSION}-linux-$(dpkg --print-architecture).tar.gz \
             | tar xz -C /usr/local/bin --strip=1 --wildcards --no-anchored etcd etcdctl \
 \
-    # Download confd
-    && curl -sL https://github.com/kelseyhightower/confd/releases/download/v${CONFDVERSION}/confd-${CONFDVERSION}-linux-$(dpkg --print-architecture) \
-            > /usr/local/bin/confd && chmod +x /usr/local/bin/confd \
+    && if [ $(dpkg --print-architecture) = 'arm64' ]; then \
+        # Build confd
+        curl -sL https://go.dev/dl/go1.20.4.linux-arm64.tar.gz | tar xz -C /usr/local go \
+        && export GOROOT=/usr/local/go && export PATH=$PATH:$GOROOT/bin \
+        && git clone --recurse-submodules https://github.com/kelseyhightower/confd.git \
+        && make -C confd \
+        && cp confd/bin/confd /usr/local/bin/confd \
+        && rm -rf /confd /usr/local/go; \
+    else \
+        # Download confd
+        curl -sL "https://github.com/kelseyhightower/confd/releases/download/v$CONFDVERSION/confd-$CONFDVERSION-linux-$(dpkg --print-architecture)" \
+            > /usr/local/bin/confd && chmod +x /usr/local/bin/confd; \
+    fi \
     # Prepare client cert for HAProxy
     && cat /etc/ssl/private/ssl-cert-snakeoil.key  /etc/ssl/certs/ssl-cert-snakeoil.pem > /etc/ssl/private/ssl-cert-snakeoil.crt \
 \
     # Clean up all useless packages and some files
     && apt-get purge -y --allow-remove-essential python3-pip gzip bzip2 util-linux e2fsprogs \
                 libmagic1 bsdmainutils login ncurses-bin libmagic-mgc e2fslibs bsdutils \
-                exim4-config gnupg-agent dirmngr libpython2.7-stdlib libpython2.7-minimal \
+                exim4-config gnupg-agent dirmngr \
+                postgresql-server-dev-$PG_MAJOR git gcc make autoconf \
+                libc6-dev flex libicu-dev libkrb5-dev liblz4-dev \
+                libpam0g-dev libreadline-dev libselinux1-dev libssl-dev libxslt1-dev libzstd-dev uuid-dev \
     && apt-get autoremove -y \
     && apt-get clean -y \
     && rm -rf /var/lib/apt/lists/* \
@@ -149,16 +175,17 @@ WORKDIR $PGHOME
 
 RUN sed -i 's/env python/&3/' /patroni*.py \
     # "fix" patroni configs
-    && sed -i 's/^\(  connect_address:\|  - host\)/#&/' postgres?.yml \
     && sed -i 's/^  listen: 127.0.0.1/  listen: 0.0.0.0/' postgres?.yml \
     && sed -i "s|^\(  data_dir: \).*|\1$PGDATA|" postgres?.yml \
     && sed -i "s|^#\(  bin_dir: \).*|\1$PGBIN|" postgres?.yml \
     && sed -i 's/^  - encoding: UTF8/  - locale: en_US.UTF-8\n&/' postgres?.yml \
     && sed -i 's/^scope:/log:\n  loggers:\n    patroni.postgresql.citus: DEBUG\n#&/' postgres?.yml \
-    && sed -i 's/^\(name\|etcd\|  host\|  authentication\|  pg_hba\|  parameters\):/#&/' postgres?.yml \
+    && sed -i 's/^\(name\|etcd\|  host\|  authentication\|  connect_address\|  parameters\):/#&/' postgres?.yml \
     && sed -i 's/^    \(replication\|superuser\|rewind\|unix_socket_directories\|\(\(  \)\{0,1\}\(username\|password\)\)\):/#&/' postgres?.yml \
     && sed -i 's/^postgresql:/&\n  basebackup:\n    checkpoint: fast/' postgres?.yml \
-    && sed -i 's|^      parameters:|      pg_hba:\n      - local all all trust\n      - hostssl replication all all md5 clientcert=verify-ca\n      - hostssl all all all md5 clientcert=verify-ca\n&\n        max_connections: 100\n        shared_buffers: 16MB\n        ssl: "on"\n        ssl_ca_file: /etc/ssl/certs/ssl-cert-snakeoil.pem\n        ssl_cert_file: /etc/ssl/certs/ssl-cert-snakeoil.pem\n        ssl_key_file: /etc/ssl/private/ssl-cert-snakeoil.key\n        citus.node_conninfo: "sslrootcert=/etc/ssl/certs/ssl-cert-snakeoil.pem sslkey=/etc/ssl/private/ssl-cert-snakeoil.key sslcert=/etc/ssl/certs/ssl-cert-snakeoil.pem sslmode=verify-ca"|'  postgres?.yml \
+    && sed -i 's|^      parameters:|&\n        max_connections: 100\n        shared_buffers: 16MB\n        ssl: "on"\n        ssl_ca_file: /etc/ssl/certs/ssl-cert-snakeoil.pem\n        ssl_cert_file: /etc/ssl/certs/ssl-cert-snakeoil.pem\n        ssl_key_file: /etc/ssl/private/ssl-cert-snakeoil.key\n        citus.node_conninfo: "sslrootcert=/etc/ssl/certs/ssl-cert-snakeoil.pem sslkey=/etc/ssl/private/ssl-cert-snakeoil.key sslcert=/etc/ssl/certs/ssl-cert-snakeoil.pem sslmode=verify-ca"|'  postgres?.yml \
+    && sed -i 's/^      pg_hba:/&\n      - local all all trust/' postgres?.yml \
+    && sed -i 's/^\(.*\) \(.*\) \(.*\) \(.*\) \(.*\) md5.*$/\1 hostssl \3 \4 all md5 clientcert=verify-ca/' postgres?.yml \
     && sed -i 's/^#\(ctl\|  certfile\|  keyfile\)/\1/' postgres?.yml \
     && sed -i 's|^#  cafile: .*$|  verify_client: required\n  cafile: /etc/ssl/certs/ssl-cert-snakeoil.pem|' postgres?.yml \
     && sed -i 's|^#  cacert: .*$|  cacert: /etc/ssl/certs/ssl-cert-snakeoil.pem|' postgres?.yml \

README.rst

@@ -8,11 +8,11 @@ You can find a version of this documentation that is searchable and also easier
 
 There are many ways to run high availability with PostgreSQL; for a list, see the `PostgreSQL Documentation <https://wiki.postgresql.org/wiki/Replication,_Clustering,_and_Connection_Pooling>`__.
 
-Patroni is a template for you to create your own customized, high-availability solution using Python and - for maximum accessibility - a distributed configuration store like `ZooKeeper <https://zookeeper.apache.org/>`__, `etcd <https://github.com/coreos/etcd>`__, `Consul <https://github.com/hashicorp/consul>`__ or `Kubernetes <https://kubernetes.io>`__. Database engineers, DBAs, DevOps engineers, and SREs who are looking to quickly deploy HA PostgreSQL in the datacenter-or anywhere else-will hopefully find it useful.
+Patroni is a template for high availability (HA) PostgreSQL solutions using Python. For maximum accessibility, Patroni supports a variety of distributed configuration stores like `ZooKeeper <https://zookeeper.apache.org/>`__, `etcd <https://github.com/coreos/etcd>`__, `Consul <https://github.com/hashicorp/consul>`__ or `Kubernetes <https://kubernetes.io>`__. Database engineers, DBAs, DevOps engineers, and SREs who are looking to quickly deploy HA PostgreSQL in datacenters - or anywhere else - will hopefully find it useful.
 
 We call Patroni a "template" because it is far from being a one-size-fits-all or plug-and-play replication system. It will have its own caveats. Use wisely.
 
-Currently supported PostgreSQL versions: 9.3 to 15.
+Currently supported PostgreSQL versions: 9.3 to 16.
 
 **Note to Citus users**: Starting from 3.0 Patroni nicely integrates with the `Citus <https://github.com/citusdata/citus>`__ database extension to Postgres. Please check the `Citus support page <https://github.com/zalando/patroni/blob/master/docs/citus.rst>`__ in the Patroni documentation for more info about how to use Patroni high availability together with a Citus distributed cluster.
 
@@ -49,7 +49,7 @@ We report new releases information `here <https://github.com/zalando/patroni/rel
 Community
 =========
 
-There are two places to connect with the Patroni community: `on github <https://github.com/zalando/patroni>`__, via Issues and PRs, and on channel `#patroni <https://postgresteam.slack.com/archives/C9XPYG92A>`__ in the `PostgreSQL Slack <https://join.slack.com/t/postgresteam/shared_invite/zt-1qj14i9sj-E9WqIFlvcOiHsEk2yFEMjA>`__.  If you're using Patroni, or just interested, please join us.
+There are two places to connect with the Patroni community: `on github <https://github.com/zalando/patroni>`__, via Issues and PRs, and on channel `#patroni <https://postgresteam.slack.com/archives/C9XPYG92A>`__ in the `PostgreSQL Slack <https://pgtreats.info/slack-invite>`__.  If you're using Patroni, or just interested, please join us.
 
 ===================================
 Technical Requirements/Installation
@@ -119,7 +119,7 @@ kubernetes
 raft
     `pysyncobj` module in order to use python Raft implementation as DCS
 aws
-    `boto` in order to use AWS callbacks
+    `boto3` in order to use AWS callbacks
 
 For example, the command in order to install Patroni together with dependencies for Etcd as a DCS and AWS callbacks is:
 

docker-compose-citus.yml

@@ -16,7 +16,7 @@ networks:
 
 services:
     etcd1: &etcd
-        image: patroni-citus
+        image: ${PATRONI_TEST_IMAGE:-patroni-citus}
         networks: [ demo ]
         environment:
             ETCDCTL_API: 3
@@ -25,6 +25,7 @@ services:
             ETCD_INITIAL_CLUSTER: etcd1=http://etcd1:2380,etcd2=http://etcd2:2380,etcd3=http://etcd3:2380
             ETCD_INITIAL_CLUSTER_STATE: new
             ETCD_INITIAL_CLUSTER_TOKEN: tutorial
+            ETCD_UNSUPPORTED_ARCH: arm64
         container_name: demo-etcd1
         hostname: etcd1
         command: etcd -name etcd1 -initial-advertise-peer-urls http://etcd1:2380
@@ -42,7 +43,7 @@ services:
         command: etcd -name etcd3 -initial-advertise-peer-urls http://etcd3:2380
 
     haproxy:
-        image: patroni-citus
+        image: ${PATRONI_TEST_IMAGE:-patroni-citus}
         networks: [ demo ]
         env_file: docker/patroni.env
         hostname: haproxy
@@ -64,7 +65,7 @@ services:
             PGSSLROOTCERT: /etc/ssl/certs/ssl-cert-snakeoil.pem
 
     coord1:
-        image: patroni-citus
+        image: ${PATRONI_TEST_IMAGE:-patroni-citus}
         networks: [ demo ]
         env_file: docker/patroni.env
         hostname: coord1
@@ -75,7 +76,7 @@ services:
             PATRONI_CITUS_GROUP: 0
 
     coord2:
-        image: patroni-citus
+        image: ${PATRONI_TEST_IMAGE:-patroni-citus}
         networks: [ demo ]
         env_file: docker/patroni.env
         hostname: coord2
@@ -85,7 +86,7 @@ services:
             PATRONI_NAME: coord2
 
     coord3:
-        image: patroni-citus
+        image: ${PATRONI_TEST_IMAGE:-patroni-citus}
         networks: [ demo ]
         env_file: docker/patroni.env
         hostname: coord3
@@ -96,7 +97,7 @@ services:
 
 
     work1-1:
-        image: patroni-citus
+        image: ${PATRONI_TEST_IMAGE:-patroni-citus}
         networks: [ demo ]
         env_file: docker/patroni.env
         hostname: work1-1
@@ -107,7 +108,7 @@ services:
             PATRONI_CITUS_GROUP: 1
 
     work1-2:
-        image: patroni-citus
+        image: ${PATRONI_TEST_IMAGE:-patroni-citus}
         networks: [ demo ]
         env_file: docker/patroni.env
         hostname: work1-2
@@ -118,7 +119,7 @@ services:
 
 
     work2-1:
-        image: patroni-citus
+        image: ${PATRONI_TEST_IMAGE:-patroni-citus}
         networks: [ demo ]
         env_file: docker/patroni.env
         hostname: work2-1
@@ -129,7 +130,7 @@ services:
             PATRONI_CITUS_GROUP: 2
 
     work2-2:
-        image: patroni-citus
+        image: ${PATRONI_TEST_IMAGE:-patroni-citus}
         networks: [ demo ]
         env_file: docker/patroni.env
         hostname: work2-2

docker-compose.yml

@@ -14,7 +14,7 @@ networks:
 
 services:
     etcd1: &etcd
-        image: patroni
+        image: ${PATRONI_TEST_IMAGE:-patroni}
         networks: [ demo ]
         environment:
             ETCD_LISTEN_PEER_URLS: http://0.0.0.0:2380
@@ -22,6 +22,7 @@ services:
             ETCD_INITIAL_CLUSTER: etcd1=http://etcd1:2380,etcd2=http://etcd2:2380,etcd3=http://etcd3:2380
             ETCD_INITIAL_CLUSTER_STATE: new
             ETCD_INITIAL_CLUSTER_TOKEN: tutorial
+            ETCD_UNSUPPORTED_ARCH: arm64
         container_name: demo-etcd1
         hostname: etcd1
         command: etcd -name etcd1 -initial-advertise-peer-urls http://etcd1:2380
@@ -39,7 +40,7 @@ services:
         command: etcd -name etcd3 -initial-advertise-peer-urls http://etcd3:2380
 
     haproxy:
-        image: patroni
+        image: ${PATRONI_TEST_IMAGE:-patroni}
         networks: [ demo ]
         env_file: docker/patroni.env
         hostname: haproxy
@@ -54,7 +55,7 @@ services:
             PATRONI_SCOPE: demo
 
     patroni1:
-        image: patroni
+        image: ${PATRONI_TEST_IMAGE:-patroni}
         networks: [ demo ]
         env_file: docker/patroni.env
         hostname: patroni1
@@ -64,7 +65,7 @@ services:
             PATRONI_NAME: patroni1
 
     patroni2:
-        image: patroni
+        image: ${PATRONI_TEST_IMAGE:-patroni}
         networks: [ demo ]
         env_file: docker/patroni.env
         hostname: patroni2
@@ -74,7 +75,7 @@ services:
             PATRONI_NAME: patroni2
 
     patroni3:
-        image: patroni
+        image: ${PATRONI_TEST_IMAGE:-patroni}
         networks: [ demo ]
         env_file: docker/patroni.env
         hostname: patroni3

docs/CONTRIBUTING.rst

@@ -1,62 +1,12 @@
 .. _contributing:
 
-Contributing guidelines
-=======================
+Contributing
+============
 
-Wanna contribute to Patroni? Yay - here is how!
+Resources and information for developers can be found in the pages below.
 
-Chatting
---------
+.. toctree::
+   :maxdepth: 2
 
-Just want to chat with other Patroni users?  Looking for interactive troubleshooting help? Join us on channel `#patroni <https://postgresteam.slack.com/archives/C9XPYG92A>`__ in the `PostgreSQL Slack <https://join.slack.com/t/postgresteam/shared_invite/zt-1qj14i9sj-E9WqIFlvcOiHsEk2yFEMjA>`__.
-
-Running tests
--------------
-
-Requirements for running behave tests:
-
-1. PostgreSQL packages need to be installed.
-2. PostgreSQL binaries must be available in your `PATH`. You may need to add them to the path with something like `PATH=/usr/lib/postgresql/11/bin:$PATH python -m behave`.
-3. If you'd like to test with external DCSs (e.g., Etcd, Consul, and Zookeeper) you'll need the packages installed and respective services running and accepting unencrypted/unprotected connections on localhost and default port. In the case of Etcd or Consul, the behave test suite could start them up if binaries are available in the `PATH`.
-
- Install dependencies:
-
-.. code-block:: bash
-
-    # You may want to use Virtualenv or specify pip3.
-    pip install -r requirements.txt
-    pip install -r requirements.dev.txt
-
-After you have all dependencies installed, you can run the various test suites:
-
-.. code-block:: bash
-
-    # You may want to use Virtualenv or specify python3.
-
-    # Run flake8 to check syntax and formatting:
-    python setup.py flake8
-
-    # Run the pytest suite in tests/:
-    python setup.py test
-
-    # Run the behave (https://behave.readthedocs.io/en/latest/) test suite in features/;
-    # modify DCS as desired (raft has no dependencies so is the easiest to start with):
-    DCS=raft python -m behave
-
-Reporting issues
-----------------
-
-If you have a question about patroni or have a problem using it, please read the :ref:`README <readme>` before filing an issue.
-Also double check with the current issues on our `Issues Tracker <https://github.com/zalando/patroni/issues>`__.
-
-Contributing a pull request
----------------------------
-
-1) Submit a comment to the relevant issue or create a new issue describing your proposed change.
-2) Do a fork, develop and test your code changes.
-3) Include documentation
-4) Submit a pull request.
-
-You'll get feedback about your pull request as soon as possible.
-
-Happy Patroni hacking ;-)
+   contributing_guidelines
+   Patroni API docs<modules/modules>

docs/ENVIRONMENT.rst

@@ -112,7 +112,11 @@ Kubernetes
 -  **PATRONI\_KUBERNETES\_NAMESPACE**: (optional) Kubernetes namespace where the Patroni pod is running. Default value is `default`.
 -  **PATRONI\_KUBERNETES\_LABELS**: Labels in format ``{label1: value1, label2: value2}``. These labels will be used to find existing objects (Pods and either Endpoints or ConfigMaps) associated with the current cluster. Also Patroni will set them on every object (Endpoint or ConfigMap) it creates.
 -  **PATRONI\_KUBERNETES\_SCOPE\_LABEL**: (optional) name of the label containing cluster name. Default value is `cluster-name`.
--  **PATRONI\_KUBERNETES\_ROLE\_LABEL**: (optional) name of the label containing Postgres role (`master` or `replica`). Patroni will set this label on the pod it is running in. Default value is `role`.
+-  **PATRONI\_KUBERNETES\_ROLE\_LABEL**: (optional) name of the label containing role (master or replica or other custom value). Patroni will set this label on the pod it runs in. Default value is ``role``.
+-  **PATRONI\_KUBERNETES\_LEADER\_LABEL\_VALUE**: (optional) value of the pod label when Postgres role is `master`. Default value is `master`.
+-  **PATRONI\_KUBERNETES\_FOLLOWER\_LABEL\_VALUE**: (optional) value of the pod label when Postgres role is `replica`. Default value is `replica`.
+-  **PATRONI\_KUBERNETES\_STANDBY\_LEADER\_LABEL\_VALUE**: (optional) value of the pod label when Postgres role is ``standby_leader``. Default value is ``master``.
+-  **PATRONI\_KUBERNETES\_TMP\_ROLE\_LABEL**: (optional) name of the temporary label containing role (master or replica). Value of this label will always use the default of corresponding role. Set only when necessary.
 -  **PATRONI\_KUBERNETES\_USE\_ENDPOINTS**: (optional) if set to true, Patroni will use Endpoints instead of ConfigMaps to run leader elections and keep cluster state.
 -  **PATRONI\_KUBERNETES\_POD\_IP**: (optional) IP address of the pod Patroni is running in. This value is required when `PATRONI_KUBERNETES_USE_ENDPOINTS` is enabled and is used to populate the leader endpoint subsets when the pod's PostgreSQL is promoted.
 -  **PATRONI\_KUBERNETES\_PORTS**: (optional) if the Service object has the name for the port, the same name must appear in the Endpoint object, otherwise service won't work. For example, if your service is defined as ``{Kind: Service, spec: {ports: [{name: postgresql, port: 5432, targetPort: 5432}]}}``, then you have to set ``PATRONI_KUBERNETES_PORTS='[{"name": "postgresql", "port": 5432}]'`` and Patroni will use it for updating subsets of the leader Endpoint. This parameter is used only if `PATRONI_KUBERNETES_USE_ENDPOINTS` is set.
@@ -135,7 +139,14 @@ PostgreSQL
 -  **PATRONI\_POSTGRESQL\_PROXY\_ADDRESS**: IP address + port through which a connection pool (e.g. pgbouncer) running next to Postgres is accessible. The value is written to the member key in DCS as ``proxy_url`` and could be used/useful for service discovery.
 -  **PATRONI\_POSTGRESQL\_DATA\_DIR**: The location of the Postgres data directory, either existing or to be initialized by Patroni.
 -  **PATRONI\_POSTGRESQL\_CONFIG\_DIR**: The location of the Postgres configuration directory, defaults to the data directory. Must be writable by Patroni.
--  **PATRONI\_POSTGRESQL\_BIN_DIR**: Path to PostgreSQL binaries. (pg_ctl, pg_rewind, pg_basebackup, postgres) The  default value is an empty string meaning that PATH environment variable will be used to find the executables.
+-  **PATRONI\_POSTGRESQL\_BIN_DIR**: Path to PostgreSQL binaries. (pg_ctl, initdb, pg_controldata, pg_basebackup, postgres, pg_isready, pg_rewind) The  default value is an empty string meaning that PATH environment variable will be used to find the executables.
+-  **PATRONI\_POSTGRESQL\_BIN\_PG\_CTL**: (optional) Custom name for ``pg_ctl`` binary.
+-  **PATRONI\_POSTGRESQL\_BIN\_INITDB**: (optional) Custom name for ``initdb`` binary.
+-  **PATRONI\_POSTGRESQL\_BIN\_PG\_CONTROLDATA**: (optional) Custom name for ``pg_controldata`` binary.
+-  **PATRONI\_POSTGRESQL\_BIN\_PG\_BASEBACKUP**: (optional) Custom name for ``pg_basebackup`` binary.
+-  **PATRONI\_POSTGRESQL\_BIN\_POSTGRES**: (optional) Custom name for ``postgres`` binary.
+-  **PATRONI\_POSTGRESQL\_BIN\_IS\_READY**: (optional) Custom name for ``pg_isready`` binary.
+-  **PATRONI\_POSTGRESQL\_BIN\_PG\_REWIND**: (optional) Custom name for ``pg_rewind`` binary.
 -  **PATRONI\_POSTGRESQL\_PGPASS**: path to the `.pgpass <https://www.postgresql.org/docs/current/static/libpq-pgpass.html>`__ password file. Patroni creates this file before executing pg\_basebackup and under some other circumstances. The location must be writable by Patroni.
 -  **PATRONI\_REPLICATION\_USERNAME**: replication username; the user will be created during initialization. Replicas will use this user to access the replication source via streaming replication
 -  **PATRONI\_REPLICATION\_PASSWORD**: replication password; the user will be created during initialization.
@@ -159,8 +170,8 @@ PostgreSQL
 -  **PATRONI\_SUPERUSER\_SSLCRLDIR**: (optional) maps to the `sslcrldir <https://www.postgresql.org/docs/current/libpq-connect.html#LIBPQ-CONNECT-SSLCRLDIR>`__ connection parameter, which specifies the location of a directory with files containing a certificate revocation list. A client will reject connecting to any server that has a certificate present in this list.
 -  **PATRONI\_SUPERUSER\_GSSENCMODE**: (optional) maps to the `gssencmode <https://www.postgresql.org/docs/current/libpq-connect.html#LIBPQ-CONNECT-GSSENCMODE>`__ connection parameter, which determines whether or with what priority a secure GSS TCP/IP connection will be negotiated with the server
 -  **PATRONI\_SUPERUSER\_CHANNEL\_BINDING**: (optional) maps to the `channel_binding <https://www.postgresql.org/docs/current/libpq-connect.html#LIBPQ-CONNECT-CHANNEL-BINDING>`__ connection parameter, which controls the client's use of channel binding.
--  **PATRONI\_REWIND\_USERNAME**: name for the user for ``pg_rewind``; the user will be created during initialization of postgres 11+ and all necessary `permissions <https://www.postgresql.org/docs/11/app-pgrewind.html#id-1.9.5.8.8>`__ will be granted.
--  **PATRONI\_REWIND\_PASSWORD**: password for the user for ``pg_rewind``; the user will be created during initialization.
+-  **PATRONI\_REWIND\_USERNAME**: (optional) name for the user for ``pg_rewind``; the user will be created during initialization of postgres 11+ and all necessary `permissions <https://www.postgresql.org/docs/11/app-pgrewind.html#id-1.9.5.8.8>`__ will be granted.
+-  **PATRONI\_REWIND\_PASSWORD**: (optional) password for the user for ``pg_rewind``; the user will be created during initialization.
 -  **PATRONI\_REWIND\_SSLMODE**: (optional) maps to the `sslmode <https://www.postgresql.org/docs/current/libpq-connect.html#LIBPQ-CONNECT-SSLMODE>`__ connection parameter, which allows a client to specify the type of TLS negotiation mode with the server. For more information on how each mode works, please visit the `PostgreSQL documentation <https://www.postgresql.org/docs/current/libpq-ssl.html#LIBPQ-SSL-SSLMODE-STATEMENTS>`__. The default mode is ``prefer``.
 -  **PATRONI\_REWIND\_SSLKEY**: (optional) maps to the `sslkey <https://www.postgresql.org/docs/current/libpq-connect.html#LIBPQ-CONNECT-SSLKEY>`__ connection parameter, which specifies the location of the secret key used with the client's certificate.
 -  **PATRONI\_REWIND\_SSLPASSWORD**: (optional) maps to the `sslpassword <https://www.postgresql.org/docs/current/libpq-connect.html#LIBPQ-CONNECT-SSLPASSWORD>`__ connection parameter, which specifies the password for the secret key specified in ``PATRONI_REWIND_SSLKEY``.
@@ -187,11 +198,21 @@ REST API
 -  **PATRONI\_RESTAPI\_ALLOWLIST\_INCLUDE\_MEMBERS**: (optional): If set to ``true`` it allows accessing unsafe REST API endpoints from other cluster members registered in DCS (IP address or hostname is taken from the members ``api_url``). Be careful, it might happen that OS will use a different IP for outgoing connections.
 -  **PATRONI\_RESTAPI\_HTTP\_EXTRA\_HEADERS**: (optional) HTTP headers let the REST API server pass additional information with an HTTP response.
 -  **PATRONI\_RESTAPI\_HTTPS\_EXTRA\_HEADERS**: (optional) HTTPS headers let the REST API server pass additional information with an HTTP response when TLS is enabled. This will also pass additional information set in ``http_extra_headers``.
+-  **PATRONI\_RESTAPI\_REQUEST\_QUEUE\_SIZE**: (optional): Sets request queue size for TCP socket used by Patroni REST API.  Once the queue is full, further requests get a "Connection denied" error. The default value is 5.
+
+.. warning::
+
+    - The ``PATRONI_RESTAPI_CONNECT_ADDRESS`` must be accessible from all nodes of a given Patroni cluster. Internally Patroni is using it during the leader race to find nodes with minimal replication lag.
+    - If you enabled client certificates validation (``PATRONI_RESTAPI_VERIFY_CLIENT`` is set to ``required``), you also **must** provide **valid client certificates** in the ``PATRONI_CTL_CERTFILE``, ``PATRONI_CTL_KEYFILE``, ``PATRONI_CTL_KEYFILE_PASSWORD``. If not provided, Patroni will not work correctly.
+
 
 CTL
 ---
--  **PATRONICTL\_CONFIG\_FILE**: location of the configuration file.
--  **PATRONI\_CTL\_INSECURE**: Allow connections to REST API without verifying SSL certs.
--  **PATRONI\_CTL\_CACERT**: Specifies the file with the CA_BUNDLE file or directory with certificates of trusted CAs to use while verifying REST API SSL certs. If not provided patronictl will use the value provided for REST API "cafile" parameter.
--  **PATRONI\_CTL\_CERTFILE**: Specifies the file with the client certificate in the PEM format. If not provided patronictl will use the value provided for REST API "certfile" parameter.
--  **PATRONI\_CTL\_KEYFILE**: Specifies the file with the client secret key in the PEM format. If not provided patronictl will use the value provided for REST API "keyfile" parameter.
+-  **PATRONICTL\_CONFIG\_FILE**: (optional) location of the configuration file.
+-  **PATRONI\_CTL\_USERNAME**: (optional) Basic-auth username for accessing protected REST API endpoints. If not provided patronictl will use the value provided for REST API "username" parameter.
+-  **PATRONI\_CTL\_PASSWORD**: (optional) Basic-auth password for accessing protected REST API endpoints. If not provided patronictl will use the value provided for REST API "password" parameter.
+-  **PATRONI\_CTL\_INSECURE**: (optional) Allow connections to REST API without verifying SSL certs.
+-  **PATRONI\_CTL\_CACERT**: (optional) Specifies the file with the CA_BUNDLE file or directory with certificates of trusted CAs to use while verifying REST API SSL certs. If not provided patronictl will use the value provided for REST API "cafile" parameter.
+-  **PATRONI\_CTL\_CERTFILE**: (optional) Specifies the file with the client certificate in the PEM format.
+-  **PATRONI\_CTL\_KEYFILE**: (optional) Specifies the file with the client secret key in the PEM format.
+-  **PATRONI\_CTL\_KEYFILE\_PASSWORD**: (optional) Specifies a password for decrypting the client keyfile.

docs/README.rst

@@ -4,7 +4,7 @@
 Introduction
 ============
 
-Patroni originated as a fork of `Governor <https://github.com/compose/governor>`__, the project from Compose. It includes plenty of new features.
+Patroni is a template for high availability (HA) PostgreSQL solutions using Python. Patroni originated as a fork of `Governor <https://github.com/compose/governor>`__, the project from Compose. It includes plenty of new features.
 
 For an example of a Docker-based deployment with Patroni, see `Spilo <https://github.com/zalando/spilo>`__, currently in use at Zalando.
 
@@ -91,7 +91,7 @@ kubernetes
 raft
     `pysyncobj` module in order to use python Raft implementation as DCS
 aws
-    `boto` in order to use AWS callbacks
+    `boto3` in order to use AWS callbacks
 
 For example, the command in order to install Patroni together with dependencies for Etcd as a DCS and AWS callbacks is:
 
@@ -145,7 +145,7 @@ run:
 YAML Configuration
 ------------------
 
-Go :ref:`here <settings>` for comprehensive information about settings for etcd, consul, and ZooKeeper. And for an example, see `postgres0.yml <https://github.com/zalando/patroni/blob/master/postgres0.yml>`__.
+Go :ref:`here <yaml_configuration>` for comprehensive information about settings for etcd, consul, and ZooKeeper. And for an example, see `postgres0.yml <https://github.com/zalando/patroni/blob/master/postgres0.yml>`__.
 
 
 Environment Configuration
@@ -179,7 +179,7 @@ That said, here are some pieces of your infrastructure you should be sure to tes
 * Network (the network in front of your system as well as the NICs [physical or virtual] themselves)
 * Disk IO
 * file limits (nofile in Linux)
-* RAM. Even if you have oomkiller turned off as suggested, the unavailability of RAM could cause issues.
+* RAM. Even if you have oomkiller turned off, the unavailability of RAM could cause issues.
 * CPU
 * Virtualization Contention (overcommitting the hypervisor)
 * Any cgroup limitation (likely to be related to the above)

docs/SETTINGS.rst

@@ -1,410 +0,0 @@
-.. _settings:
-
-===========================
-YAML Configuration Settings
-===========================
-
-.. _dynamic_configuration_settings:
-
-Dynamic configuration settings
-------------------------------
-
-Dynamic configuration is stored in the DCS (Distributed Configuration Store) and applied on all cluster nodes. Some parameters, like **loop_wait**, **ttl**, **postgresql.parameters.max_connections**, **postgresql.parameters.max_worker_processes** and so on could be set only in the dynamic configuration. Some other parameters like **postgresql.listen**, **postgresql.data_dir** could be set only locally, i.e. in the Patroni config file or via :ref:`configuration <environment>` variable. In most cases the local configuration will override the dynamic configuration. In order to change the dynamic configuration you can use either ``patronictl edit-config`` tool or Patroni :ref:`REST API <rest_api>`.
-
--  **loop\_wait**: the number of seconds the loop will sleep. Default value: 10
--  **ttl**: the TTL to acquire the leader lock (in seconds). Think of it as the length of time before initiation of the automatic failover process. Default value: 30
--  **retry\_timeout**: timeout for DCS and PostgreSQL operation retries (in seconds). DCS or network issues shorter than this will not cause Patroni to demote the leader. Default value: 10
--  **maximum\_lag\_on\_failover**: the maximum bytes a follower may lag to be able to participate in leader election.
--  **maximum\_lag\_on\_syncnode**: the maximum bytes a synchronous follower may lag before it is considered as an unhealthy candidate and swapped by healthy asynchronous follower. Patroni utilize the max replica lsn if there is more than one follower, otherwise it will use leader's current wal lsn. Default is -1, Patroni will not take action to swap synchronous unhealthy follower when the value is set to 0 or below. Please set the value high enough so Patroni won't swap synchrounous follower fequently during high transaction volume.
--  **max\_timelines\_history**: maximum number of timeline history items kept in DCS.  Default value: 0. When set to 0, it keeps the full history in DCS.
--  **primary\_start\_timeout**: the amount of time a primary is allowed to recover from failures before failover is triggered (in seconds). Default is 300 seconds. When set to 0 failover is done immediately after a crash is detected if possible. When using asynchronous replication a failover can cause lost transactions. Worst case failover time for primary failure is: loop\_wait + primary\_start\_timeout + loop\_wait, unless primary\_start\_timeout is zero, in which case it's just loop\_wait. Set the value according to your durability/availability tradeoff.
-- **primary\_stop\_timeout**: The number of seconds Patroni is allowed to wait when stopping Postgres and effective only when synchronous_mode is enabled. When set to > 0 and the synchronous_mode is enabled, Patroni sends SIGKILL to the postmaster if the stop operation is running for more than the value set by primary\_stop\_timeout. Set the value according to your durability/availability tradeoff. If the parameter is not set or set <= 0, primary\_stop\_timeout does not apply.
--  **synchronous\_mode**: turns on synchronous replication mode. In this mode a replica will be chosen as synchronous and only the latest leader and synchronous replica are able to participate in leader election. Synchronous mode makes sure that successfully committed transactions will not be lost at failover, at the cost of losing availability for writes when Patroni cannot ensure transaction durability. See :ref:`replication modes documentation <replication_modes>` for details.
--  **synchronous\_mode\_strict**: prevents disabling synchronous replication if no synchronous replicas are available, blocking all client writes to the primary. See :ref:`replication modes documentation <replication_modes>` for details.
--  **failsafe\_mode**: Enables :ref:`DCS Failsafe Mode <dcs_failsafe_mode>`. Defaults to `false`.
--  **postgresql**:
-    -  **use\_pg\_rewind**: whether or not to use pg_rewind. Defaults to `false`.
-    -  **use\_slots**: whether or not to use replication slots. Defaults to `true` on PostgreSQL 9.4+.
-    -  **recovery\_conf**: additional configuration settings written to recovery.conf when configuring follower. There is no recovery.conf anymore in PostgreSQL 12, but you may continue using this section, because Patroni handles it transparently.
-    -  **parameters**: list of configuration settings for Postgres.
--  **standby\_cluster**: if this section is defined, we want to bootstrap a standby cluster.
-    -  **host**: an address of remote node
-    -  **port**: a port of remote node
-    -  **primary\_slot\_name**: which slot on the remote node to use for replication. This parameter is optional, the default value is derived from the instance name (see function `slot_name_from_member_name`).
-    -  **create\_replica\_methods**: an ordered list of methods that can be used to bootstrap standby leader from the remote primary, can be different from the list defined in :ref:`postgresql_settings`
-    -  **restore\_command**: command to restore WAL records from the remote primary to nodes in a standby cluster, can be different from the list defined in :ref:`postgresql_settings`
-    -  **archive\_cleanup\_command**: cleanup command for standby leader
-    -  **recovery\_min\_apply\_delay**: how long to wait before actually apply WAL records on a standby leader
--  **slots**: define permanent replication slots. These slots will be preserved during switchover/failover. The logical slots are copied from the primary to a standby with restart, and after that their position advanced every **loop_wait** seconds (if necessary). Copying logical slot files performed via ``libpq`` connection and using either rewind or superuser credentials (see **postgresql.authentication** section). There is always a chance that the logical slot position on the replica is a bit behind the former primary, therefore application should be prepared that some messages could be received the second time after the failover. The easiest way of doing so - tracking ``confirmed_flush_lsn``. Enabling permanent logical replication slots requires **postgresql.use_slots** to be set and will also automatically enable the ``hot_standby_feedback``. Since the failover of logical replication slots is unsafe on PostgreSQL 9.6 and older and PostgreSQL version 10 is missing some important functions, the feature only works with PostgreSQL 11+.
-    -  **my_slot_name**: the name of replication slot. If the permanent slot name matches with the name of the current primary it will not be created. Everything else is the responsibility of the operator to make sure that there are no clashes in names between replication slots automatically created by Patroni for members and permanent replication slots.
-        -  **type**: slot type. Could be ``physical`` or ``logical``. If the slot is logical, you have to additionally define ``database`` and ``plugin``.
-        -  **database**: the database name where logical slots should be created.
-        -  **plugin**: the plugin name for the logical slot.
--  **ignore_slots**: list of sets of replication slot properties for which Patroni should ignore matching slots. This configuration/feature/etc. is useful when some replication slots are managed outside of Patroni. Any subset of matching properties will cause a slot to be ignored.
-    -  **name**: the name of the replication slot.
-    -  **type**: slot type. Can be ``physical`` or ``logical``. If the slot is logical, you may additionally define ``database`` and/or ``plugin``.
-    -  **database**: the database name (when matching a ``logical`` slot).
-    -  **plugin**: the logical decoding plugin (when matching a ``logical`` slot).
-
-Note: **slots** is a hashmap while **ignore_slots** is an array. For example:
-
-.. code:: YAML
-
-        slots:
-          permanent_logical_slot_name:
-            type: logical
-            database: my_db
-            plugin: test_decoding
-          permanent_physical_slot_name:
-            type: physical
-          ...
-        ignore_slots:
-          - name: ignored_logical_slot_name
-            type: logical
-            database: my_db
-            plugin: test_decoding
-          - name: ignored_physical_slot_name
-            type: physical
-          ...
-
-Global/Universal
-----------------
--  **name**: the name of the host. Must be unique for the cluster.
--  **namespace**: path within the configuration store where Patroni will keep information about the cluster. Default value: "/service"
--  **scope**: cluster name
-
-Log
----
--  **level**: sets the general logging level. Default value is **INFO** (see `the docs for Python logging <https://docs.python.org/3.6/library/logging.html#levels>`_)
--  **traceback\_level**: sets the level where tracebacks will be visible. Default value is **ERROR**. Set it to **DEBUG** if you want to see tracebacks only if you enable **log.level=DEBUG**.
--  **format**: sets the log formatting string. Default value is **%(asctime)s %(levelname)s: %(message)s** (see `the LogRecord attributes <https://docs.python.org/3.6/library/logging.html#logrecord-attributes>`_)
--  **dateformat**: sets the datetime formatting string. (see the `formatTime() documentation <https://docs.python.org/3.6/library/logging.html#logging.Formatter.formatTime>`_)
--  **max\_queue\_size**: Patroni is using two-step logging. Log records are written into the in-memory queue and there is a separate thread which pulls them from the queue and writes to stderr or file. The maximum size of the internal queue is limited by default by **1000** records, which is enough to keep logs for the past 1h20m.
--  **dir**: Directory to write application logs to. The directory must exist and be writable by the user executing Patroni. If you set this value, the application will retain 4 25MB logs by default. You can tune those retention values with `file_num` and `file_size` (see below).
--  **file\_num**: The number of application logs to retain.
--  **file\_size**: Size of patroni.log file (in bytes) that triggers a log rolling.
--  **loggers**: This section allows redefining logging level per python module
-    -  **patroni.postmaster: WARNING**
-    -  **urllib3: DEBUG**
-
-.. _bootstrap_settings:
-
-Bootstrap configuration
------------------------
--  **bootstrap**:
-    -  **dcs**: This section will be written into `/<namespace>/<scope>/config` of the given configuration store after initializing of new cluster. The global dynamic configuration for the cluster. Under the ``bootstrap.dcs`` you can put any of the parameters described in the :ref:`Dynamic Configuration settings <dynamic_configuration_settings>` and after Patroni initialized (bootstrapped) the new cluster, it will write this section into `/<namespace>/<scope>/config` of the configuration store. All later changes of ``bootstrap.dcs`` will not take any effect! If you want to change them please use either ``patronictl edit-config`` or Patroni :ref:`REST API <rest_api>`.
-    -  **method**: custom script to use for bootstrapping this cluster.
-       See :ref:`custom bootstrap methods documentation <custom_bootstrap>` for details.
-       When ``initdb`` is specified revert to the default ``initdb`` command. ``initdb`` is also triggered when no ``method``
-       parameter is present in the configuration file.
-    -  **initdb**: List options to be passed on to initdb.
-            -  **- data-checksums**: Must be enabled when pg_rewind is needed on 9.3.
-            -  **- encoding: UTF8**: default encoding for new databases.
-            -  **- locale: UTF8**: default locale for new databases.
-    -  **pg\_hba**: list of lines that you should add to pg\_hba.conf.
-            -  **- host all all 0.0.0.0/0 md5**.
-            -  **- host replication replicator 127.0.0.1/32 md5**: A line like this is required for replication.
-    -  **users**: Some additional users which need to be created after initializing new cluster
-        -  **admin**: the name of user
-            -  **password: zalando**:
-            -  **options**: list of options for CREATE USER statement
-                -  **- createrole**
-                -  **- createdb**
-    -  **post\_bootstrap** or **post\_init**: An additional script that will be executed after initializing the cluster. The script receives a connection string URL (with the cluster superuser as a user name). The PGPASSFILE variable is set to the location of pgpass file.
-
-.. _citus_settings:
-
-Citus
------
-Enables integration Patroni with `Citus <https://docs.citusdata.com>`__. If configured, Patroni will take care of registering Citus worker nodes on the coordinator. You can find more information about Citus support :ref:`here <citus>`.
-
--  **group**: the Citus group id, integer. Use ``0`` for coordinator and ``1``, ``2``, etc... for workers
--  **database**: the database where ``citus`` extension should be created. Must be the same on the coordinator and all workers. Currently only one database is supported.
-
-.. _consul_settings:
-
-Consul
-------
-Most of the parameters are optional, but you have to specify one of the **host** or **url**
-
--  **host**: the host:port for the Consul local agent.
--  **url**: url for the Consul local agent, in format: http(s)://host:port.
--  **port**: (optional) Consul port.
--  **scheme**: (optional) **http** or **https**, defaults to **http**.
--  **token**: (optional) ACL token.
--  **verify**: (optional) whether to verify the SSL certificate for HTTPS requests.
--  **cacert**: (optional) The ca certificate. If present it will enable validation.
--  **cert**: (optional) file with the client certificate.
--  **key**: (optional) file with the client key. Can be empty if the key is part of **cert**.
--  **dc**: (optional) Datacenter to communicate with. By default the datacenter of the host is used.
--  **consistency**: (optional) Select consul consistency mode. Possible values are ``default``, ``consistent``, or ``stale`` (more details in `consul API reference <https://www.consul.io/api/features/consistency.html/>`__)
--  **checks**: (optional) list of Consul health checks used for the session. By default an empty list is used.
--  **register\_service**: (optional) whether or not to register a service with the name defined by the scope parameter and the tag master, primary, replica, or standby-leader depending on the node's role. Defaults to **false**.
--  **service\_tags**: (optional) additional static tags to add to the Consul service apart from the role (``master``/``primary``/``replica``/``standby-leader``). By default an empty list is used.
--  **service\_check\_interval**: (optional) how often to perform health check against registered url. Defaults to '5s'.
--  **service\_check\_tls\_server\_name**: (optional) overide SNI host when connecting via TLS, see also `consul agent check API reference <https://www.consul.io/api-docs/agent/check#tlsservername>`__.
-
-The ``token`` needs to have the following ACL permissions:
-
-::
-
-    service_prefix "${scope}" {
-        policy = "write"
-    }
-    key_prefix "${namespace}/${scope}" {
-        policy = "write"
-    }
-    session_prefix "" {
-        policy = "write"
-    }
-
-Etcd
-----
-Most of the parameters are optional, but you have to specify one of the **host**, **hosts**, **url**, **proxy** or **srv**
-
--  **host**: the host:port for the etcd endpoint.
--  **hosts**: list of etcd endpoint in format host1:port1,host2:port2,etc... Could be a comma separated string or an actual yaml list.
--  **use\_proxies**: If this parameter is set to true, Patroni will consider **hosts** as a list of proxies and will not perform a topology discovery of etcd cluster.
--  **url**: url for the etcd.
--  **proxy**: proxy url for the etcd. If you are connecting to the etcd using proxy, use this parameter instead of **url**.
--  **srv**: Domain to search the SRV record(s) for cluster autodiscovery. Patroni will try to query these SRV service names for specified domain (in that order until first success): ``_etcd-client-ssl``, ``_etcd-client``, ``_etcd-ssl``, ``_etcd``, ``_etcd-server-ssl``, ``_etcd-server``. If SRV records for ``_etcd-server-ssl`` or ``_etcd-server`` are retrieved then ETCD peer protocol is used do query ETCD for available members. Otherwise hosts from SRV records will be used.
--  **srv\_suffix**: Configures a suffix to the SRV name that is queried during discovery. Use this flag to differentiate between multiple etcd clusters under the same domain. Works only with conjunction with **srv**. For example, if ``srv_suffix: foo`` and ``srv: example.org`` are set, the following DNS SRV query is made:``_etcd-client-ssl-foo._tcp.example.com`` (and so on for every possible ETCD SRV service name).
--  **protocol**: (optional) http or https, if not specified http is used. If the **url** or **proxy** is specified - will take protocol from them.
--  **username**: (optional) username for etcd authentication.
--  **password**: (optional) password for etcd authentication.
--  **cacert**: (optional) The ca certificate. If present it will enable validation.
--  **cert**: (optional) file with the client certificate.
--  **key**: (optional) file with the client key. Can be empty if the key is part of **cert**.
-
-Etcdv3
-------
-If you want that Patroni works with Etcd cluster via protocol version 3, you need to use the ``etcd3`` section in the Patroni configuration file. All configuration parameters are the same as for ``etcd``.
-
-.. warning::
-    Keys created with protocol version 2 are not visible with protocol version 3 and the other way around, therefore it is not possible to switch from ``etcd`` to ``etcd3`` just by updating Patroni config file.
-
-
-ZooKeeper
-----------
--  **hosts**: List of ZooKeeper cluster members in format: ['host1:port1', 'host2:port2', 'etc...'].
--  **use_ssl**: (optional) Whether SSL is used or not. Defaults to ``false``. If set to ``false``, all SSL specific parameters are ignored.
--  **cacert**: (optional) The CA certificate. If present it will enable validation.
--  **cert**: (optional) File with the client certificate.
--  **key**: (optional) File with the client key.
--  **key_password**: (optional) The client key password.
--  **verify**: (optional) Whether to verify certificate or not. Defaults to ``true``.
--  **set_acls**: (optional) If set, configure Kazoo to apply a default ACL to each ZNode that it creates. ACLs will assume 'x509' schema and should be specified as a dictionary with the principal as the key and one or more permissions as a list in the value.  Permissions may be one of ``CREATE``, ``READ``, ``WRITE``, ``DELETE`` or ``ADMIN``.  For example, ``set_acls: {CN=principal1: [CREATE, READ], CN=principal2: [ALL]}``.
-
-.. note::
-    It is required to install ``kazoo>=2.6.0`` to support SSL.
-
-
-Exhibitor
----------
--  **hosts**: initial list of Exhibitor (ZooKeeper) nodes in format: 'host1,host2,etc...'. This list updates automatically whenever the Exhibitor (ZooKeeper) cluster topology changes.
--  **poll\_interval**: how often the list of ZooKeeper and Exhibitor nodes should be updated from Exhibitor.
--  **port**: Exhibitor port.
-
-.. _kubernetes_settings:
-
-Kubernetes
-----------
--  **bypass\_api\_service**: (optional) When communicating with the Kubernetes API, Patroni is usually relying on the `kubernetes` service, the address of which is exposed in the pods via the `KUBERNETES_SERVICE_HOST` environment variable. If `bypass_api_service` is set to ``true``, Patroni will resolve the list of API nodes behind the service and connect directly to them.
--  **namespace**: (optional) Kubernetes namespace where Patroni pod is running. Default value is `default`.
--  **labels**: Labels in format ``{label1: value1, label2: value2}``. These labels will be used to find existing objects (Pods and either Endpoints or ConfigMaps) associated with the current cluster. Also Patroni will set them on every object (Endpoint or ConfigMap) it creates.
--  **scope\_label**: (optional) name of the label containing cluster name. Default value is `cluster-name`.
--  **role\_label**: (optional) name of the label containing role (master or replica). Patroni will set this label on the pod it runs in. Default value is ``role``.
--  **use\_endpoints**: (optional) if set to true, Patroni will use Endpoints instead of ConfigMaps to run leader elections and keep cluster state.
--  **pod\_ip**: (optional) IP address of the pod Patroni is running in. This value is required when `use_endpoints` is enabled and is used to populate the leader endpoint subsets when the pod's PostgreSQL is promoted.
--  **ports**: (optional) if the Service object has the name for the port, the same name must appear in the Endpoint object, otherwise service won't work. For example, if your service is defined as ``{Kind: Service, spec: {ports: [{name: postgresql, port: 5432, targetPort: 5432}]}}``, then you have to set ``kubernetes.ports: [{"name": "postgresql", "port": 5432}]`` and Patroni will use it for updating subsets of the leader Endpoint. This parameter is used only if `kubernetes.use_endpoints` is set.
--  **cacert**: (optional) Specifies the file with the CA_BUNDLE file with certificates of trusted CAs to use while verifying Kubernetes API SSL certs. If not provided, patroni will use the value provided by the ServiceAccount secret.
--  **retriable\_http\_codes**: (optional) list of HTTP status codes from K8s API to retry on. By default Patroni is retrying on ``500``, ``503``, and ``504``, or if K8s API response has ``retry-after`` HTTP header.
-
-
-.. _raft_settings:
-
-Raft (deprecated)
------------------
--  **self\_addr**: ``ip:port`` to listen on for Raft connections. The ``self_addr`` must be accessible from other nodes of the cluster. If not set, the node will not participate in consensus.
--  **bind\_addr**: (optional) ``ip:port`` to listen on for Raft connections. If not specified the ``self_addr`` will be used.
--  **partner\_addrs**: list of other Patroni nodes in the cluster in format: ['ip1:port', 'ip2:port', 'etc...']
--  **data\_dir**: directory where to store Raft log and snapshot. If not specified the current working directory is used.
--  **password**: (optional) Encrypt Raft traffic with a specified password, requires ``cryptography`` python module.
-
-  Short FAQ about Raft implementation
-
-  - Q: How to list all the nodes providing consensus?
-
-    A: ``syncobj_admin -conn host:port -status`` where the host:port is the address of one of the cluster nodes
-
-  - Q: Node that was a part of consensus and has gone and I can't reuse the same IP for other node. How to remove this node from the consensus?
-
-    A: ``syncobj_admin -conn host:port -remove host2:port2`` where the ``host2:port2`` is the address of the node you want to remove from consensus.
-
-  - Q: Where to get the ``syncobj_admin`` utility?
-
-    A: It is installed together with ``pysyncobj`` module (python RAFT implementation), which is Patroni dependency.
-
-  - Q: it is possible to run Patroni node without adding in to the consensus?
-
-    A: Yes, just comment out or remove ``raft.self_addr`` from Patroni configuration.
-
-  - Q: It is possible to run Patroni and PostgreSQL only on two nodes?
-
-    A: Yes, on the third node you can run ``patroni_raft_controller`` (without Patroni and PostgreSQL). In such a setup, one can temporarily lose one node without affecting the primary.
-
-
-.. _postgresql_settings:
-
-PostgreSQL
-----------
--  **postgresql**:
-    -  **authentication**:
-        -  **superuser**:
-            -  **username**: name for the superuser, set during initialization (initdb) and later used by Patroni to connect to the postgres.
-            -  **password**: password for the superuser, set during initialization (initdb).
-            -  **sslmode**: (optional) maps to the `sslmode <https://www.postgresql.org/docs/current/libpq-connect.html#LIBPQ-CONNECT-SSLMODE>`__ connection parameter, which allows a client to specify the type of TLS negotiation mode with the server. For more information on how each mode works, please visit the `PostgreSQL documentation <https://www.postgresql.org/docs/current/libpq-ssl.html#LIBPQ-SSL-SSLMODE-STATEMENTS>`__. The default mode is ``prefer``.
-            -  **sslkey**: (optional) maps to the `sslkey <https://www.postgresql.org/docs/current/libpq-connect.html#LIBPQ-CONNECT-SSLKEY>`__ connection parameter, which specifies the location of the secret key used with the client's certificate.
-            -  **sslpassword**: (optional) maps to the `sslpassword <https://www.postgresql.org/docs/current/libpq-connect.html#LIBPQ-CONNECT-SSLPASSWORD>`__ connection parameter, which specifies the password for the secret key specified in ``sslkey``.
-            -  **sslcert**: (optional) maps to the `sslcert <https://www.postgresql.org/docs/current/libpq-connect.html#LIBPQ-CONNECT-SSLCERT>`__ connection parameter, which specifies the location of the client certificate.
-            -  **sslrootcert**: (optional) maps to the `sslrootcert <https://www.postgresql.org/docs/current/libpq-connect.html#LIBPQ-CONNECT-SSLROOTCERT>`__ connection parameter, which specifies the location of a file containing one ore more certificate authorities (CA) certificates that the client will use to verify a server's certificate.
-            -  **sslcrl**: (optional) maps to the `sslcrl <https://www.postgresql.org/docs/current/libpq-connect.html#LIBPQ-CONNECT-SSLCRL>`__ connection parameter, which specifies the location of a file containing a certificate revocation list. A client will reject connecting to any server that has a certificate present in this list.
-            -  **sslcrldir**: (optional) maps to the `sslcrldir <https://www.postgresql.org/docs/current/libpq-connect.html#LIBPQ-CONNECT-SSLCRLDIR>`__ connection parameter, which specifies the location of a directory with files containing a certificate revocation list. A client will reject connecting to any server that has a certificate present in this list.
-            -  **gssencmode**: (optional) maps to the `gssencmode <https://www.postgresql.org/docs/current/libpq-connect.html#LIBPQ-CONNECT-GSSENCMODE>`__ connection parameter, which determines whether or with what priority a secure GSS TCP/IP connection will be negotiated with the server
-            -  **channel_binding**: (optional) maps to the `channel_binding <https://www.postgresql.org/docs/current/libpq-connect.html#LIBPQ-CONNECT-CHANNEL-BINDING>`__ connection parameter, which controls the client's use of channel binding.
-        -  **replication**:
-            -  **username**: replication username; the user will be created during initialization. Replicas will use this user to access the replication source via streaming replication
-            -  **password**: replication password; the user will be created during initialization.
-            -  **sslmode**: (optional) maps to the `sslmode <https://www.postgresql.org/docs/current/libpq-connect.html#LIBPQ-CONNECT-SSLMODE>`__ connection parameter, which allows a client to specify the type of TLS negotiation mode with the server. For more information on how each mode works, please visit the `PostgreSQL documentation <https://www.postgresql.org/docs/current/libpq-ssl.html#LIBPQ-SSL-SSLMODE-STATEMENTS>`__. The default mode is ``prefer``.
-            -  **sslkey**: (optional) maps to the `sslkey <https://www.postgresql.org/docs/current/libpq-connect.html#LIBPQ-CONNECT-SSLKEY>`__ connection parameter, which specifies the location of the secret key used with the client's certificate.
-            -  **sslpassword**: (optional) maps to the `sslpassword <https://www.postgresql.org/docs/current/libpq-connect.html#LIBPQ-CONNECT-SSLPASSWORD>`__ connection parameter, which specifies the password for the secret key specified in ``sslkey``.
-            -  **sslcert**: (optional) maps to the `sslcert <https://www.postgresql.org/docs/current/libpq-connect.html#LIBPQ-CONNECT-SSLCERT>`__ connection parameter, which specifies the location of the client certificate.
-            -  **sslrootcert**: (optional) maps to the `sslrootcert <https://www.postgresql.org/docs/current/libpq-connect.html#LIBPQ-CONNECT-SSLROOTCERT>`__ connection parameter, which specifies the location of a file containing one ore more certificate authorities (CA) certificates that the client will use to verify a server's certificate.
-            -  **sslcrl**: (optional) maps to the `sslcrl <https://www.postgresql.org/docs/current/libpq-connect.html#LIBPQ-CONNECT-SSLCRL>`__ connection parameter, which specifies the location of a file containing a certificate revocation list. A client will reject connecting to any server that has a certificate present in this list.
-            -  **sslcrldir**: (optional) maps to the `sslcrldir <https://www.postgresql.org/docs/current/libpq-connect.html#LIBPQ-CONNECT-SSLCRLDIR>`__ connection parameter, which specifies the location of a directory with files containing a certificate revocation list. A client will reject connecting to any server that has a certificate present in this list.
-            -  **gssencmode**: (optional) maps to the `gssencmode <https://www.postgresql.org/docs/current/libpq-connect.html#LIBPQ-CONNECT-GSSENCMODE>`__ connection parameter, which determines whether or with what priority a secure GSS TCP/IP connection will be negotiated with the server
-            -  **channel_binding**: (optional) maps to the `channel_binding <https://www.postgresql.org/docs/current/libpq-connect.html#LIBPQ-CONNECT-CHANNEL-BINDING>`__ connection parameter, which controls the client's use of channel binding.
-        -  **rewind**:
-            -  **username**: name for the user for ``pg_rewind``; the user will be created during initialization of postgres 11+ and all necessary `permissions <https://www.postgresql.org/docs/11/app-pgrewind.html#id-1.9.5.8.8>`__ will be granted.
-            -  **password**: password for the user for ``pg_rewind``; the user will be created during initialization.
-            -  **sslmode**: (optional) maps to the `sslmode <https://www.postgresql.org/docs/current/libpq-connect.html#LIBPQ-CONNECT-SSLMODE>`__ connection parameter, which allows a client to specify the type of TLS negotiation mode with the server. For more information on how each mode works, please visit the `PostgreSQL documentation <https://www.postgresql.org/docs/current/libpq-ssl.html#LIBPQ-SSL-SSLMODE-STATEMENTS>`__. The default mode is ``prefer``.
-            -  **sslkey**: (optional) maps to the `sslkey <https://www.postgresql.org/docs/current/libpq-connect.html#LIBPQ-CONNECT-SSLKEY>`__ connection parameter, which specifies the location of the secret key used with the client's certificate.
-            -  **sslpassword**: (optional) maps to the `sslpassword <https://www.postgresql.org/docs/current/libpq-connect.html#LIBPQ-CONNECT-SSLPASSWORD>`__ connection parameter, which specifies the password for the secret key specified in ``sslkey``.
-            -  **sslcert**: (optional) maps to the `sslcert <https://www.postgresql.org/docs/current/libpq-connect.html#LIBPQ-CONNECT-SSLCERT>`__ connection parameter, which specifies the location of the client certificate.
-            -  **sslrootcert**: (optional) maps to the `sslrootcert <https://www.postgresql.org/docs/current/libpq-connect.html#LIBPQ-CONNECT-SSLROOTCERT>`__ connection parameter, which specifies the location of a file containing one ore more certificate authorities (CA) certificates that the client will use to verify a server's certificate.
-            -  **sslcrl**: (optional) maps to the `sslcrl <https://www.postgresql.org/docs/current/libpq-connect.html#LIBPQ-CONNECT-SSLCRL>`__ connection parameter, which specifies the location of a file containing a certificate revocation list. A client will reject connecting to any server that has a certificate present in this list.
-            -  **sslcrldir**: (optional) maps to the `sslcrldir <https://www.postgresql.org/docs/current/libpq-connect.html#LIBPQ-CONNECT-SSLCRLDIR>`__ connection parameter, which specifies the location of a directory with files containing a certificate revocation list. A client will reject connecting to any server that has a certificate present in this list.
-            -  **gssencmode**: (optional) maps to the `gssencmode <https://www.postgresql.org/docs/current/libpq-connect.html#LIBPQ-CONNECT-GSSENCMODE>`__ connection parameter, which determines whether or with what priority a secure GSS TCP/IP connection will be negotiated with the server
-            -  **channel_binding**: (optional) maps to the `channel_binding <https://www.postgresql.org/docs/current/libpq-connect.html#LIBPQ-CONNECT-CHANNEL-BINDING>`__ connection parameter, which controls the client's use of channel binding.
-    -  **callbacks**: callback scripts to run on certain actions. Patroni will pass the action, role and cluster name. (See scripts/aws.py as an example of how to write them.)
-            -  **on\_reload**: run this script when configuration reload is triggered.
-            -  **on\_restart**: run this script when the postgres restarts (without changing role).
-            -  **on\_role\_change**: run this script when the postgres is being promoted or demoted.
-            -  **on\_start**: run this script when the postgres starts.
-            -  **on\_stop**: run this script when the postgres stops.
-    -  **connect\_address**: IP address + port through which Postgres is accessible from other nodes and applications.
-    -  **proxy\_address**: IP address + port through which a connection pool (e.g. pgbouncer) running next to Postgres is accessible. The value is written to the member key in DCS as ``proxy_url`` and could be used/useful for service discovery.
-    -  **create\_replica\_methods**: an ordered list of the create methods for turning a Patroni node into a new replica.
-       "basebackup" is the default method; other methods are assumed to refer to scripts, each of which is configured as its
-       own config item. See :ref:`custom replica creation methods documentation <custom_replica_creation>` for further explanation.
-    -  **data\_dir**: The location of the Postgres data directory, either :ref:`existing <existing_data>` or to be initialized by Patroni.
-    -  **config\_dir**: The location of the Postgres configuration directory, defaults to the data directory. Must be writable by Patroni.
-    -  **bin\_dir**: Path to PostgreSQL binaries (pg_ctl, pg_rewind, pg_basebackup, postgres). The default value is an empty string meaning that PATH environment variable will be used to find the executables.
-    -  **listen**: IP address + port that Postgres listens to; must be accessible from other nodes in the cluster, if you're using streaming replication. Multiple comma-separated addresses are permitted, as long as the port component is appended after to the last one with a colon, i.e. ``listen: 127.0.0.1,127.0.0.2:5432``. Patroni will use the first address from this list to establish local connections to the PostgreSQL node.
-    -  **use\_unix\_socket**: specifies that Patroni should prefer to use unix sockets to connect to the cluster. Default value is ``false``. If ``unix_socket_directories`` is defined, Patroni will use the first suitable value from it to connect to the cluster and fallback to tcp if nothing is suitable. If ``unix_socket_directories`` is not specified in ``postgresql.parameters``, Patroni will assume that the default value should be used and omit ``host`` from the connection parameters.
-    -  **use\_unix\_socket\_repl**: specifies that Patroni should prefer to use unix sockets for replication user cluster connection. Default value is ``false``. If ``unix_socket_directories`` is defined, Patroni will use the first suitable value from it to connect to the cluster and fallback to tcp if nothing is suitable. If ``unix_socket_directories`` is not specified in ``postgresql.parameters``, Patroni will assume that the default value should be used and omit ``host`` from the connection parameters.
-    -  **pgpass**: path to the `.pgpass <https://www.postgresql.org/docs/current/static/libpq-pgpass.html>`__ password file. Patroni creates this file before executing pg\_basebackup, the post_init script and under some other circumstances. The location must be writable by Patroni.
-    -  **recovery\_conf**: additional configuration settings written to recovery.conf when configuring follower.
-    -  **custom\_conf** : path to an optional custom ``postgresql.conf`` file, that will be used in place of ``postgresql.base.conf``. The file must exist on all cluster nodes, be readable by PostgreSQL and will be included from its location on the real ``postgresql.conf``. Note that Patroni will not monitor this file for changes, nor backup it. However, its settings can still be overridden by Patroni's own configuration facilities - see :ref:`dynamic configuration <dynamic_configuration>` for details.
-    -  **parameters**: list of configuration settings for Postgres. Many of these are required for replication to work.
-    -  **pg\_hba**: list of lines that Patroni will use to generate ``pg_hba.conf``. This parameter has higher priority than ``bootstrap.pg_hba``. Together with :ref:`dynamic configuration <dynamic_configuration>` it simplifies management of ``pg_hba.conf``.
-            -  **- host all all 0.0.0.0/0 md5**.
-            -  **- host replication replicator 127.0.0.1/32 md5**: A line like this is required for replication.
-    -  **pg\_ident**: list of lines that Patroni will use to generate ``pg_ident.conf``. Together with :ref:`dynamic configuration <dynamic_configuration>` it simplifies management of ``pg_ident.conf``.
-            -  **- mapname1 systemname1 pguser1**.
-            -  **- mapname1 systemname2 pguser2**.
-    -  **pg\_ctl\_timeout**: How long should pg_ctl wait when doing ``start``, ``stop`` or ``restart``. Default value is 60 seconds.
-    -  **use\_pg\_rewind**: try to use pg\_rewind on the former leader when it joins cluster as a replica.
-    -  **remove\_data\_directory\_on\_rewind\_failure**: If this option is enabled, Patroni will remove the PostgreSQL data directory and recreate the replica. Otherwise it will try to follow the new leader. Default value is **false**.
-    -  **remove\_data\_directory\_on\_diverged\_timelines**: Patroni will remove the PostgreSQL data directory and recreate the replica if it notices that timelines are diverging and the former primary can not start streaming from the new primary. This option is useful when ``pg_rewind`` can not be used. While performing timelines divergence check on PostgreSQL v10 and older Patroni will try to connect with replication credential to the "postgres" database. Hence, such access should be allowed in the  pg_hba.conf. Default value is **false**.
-    -  **replica\_method**: for each create_replica_methods other than basebackup, you would add a configuration section of the same name. At a minimum, this should include "command" with a full path to the actual script to be executed. Other configuration parameters will be passed along to the script in the form "parameter=value".
-    -  **pre\_promote**: a fencing script that executes during a failover after acquiring the leader lock but before promoting the replica. If the script exits with a non-zero code, Patroni does not promote the replica and removes the leader key from DCS.
-
-.. _restapi_settings:
-
-REST API
---------
--  **restapi**:
-        -  **connect\_address**: IP address (or hostname) and port, to access the Patroni's :ref:`REST API <rest_api>`. All the members of the cluster must be able to connect to this address, so unless the Patroni setup is intended for a demo inside the localhost, this address must be a non "localhost" or loopback address (ie: "localhost" or "127.0.0.1"). It can serve as an endpoint for HTTP health checks (read below about the "listen" REST API parameter), and also for user queries (either directly or via the REST API), as well as for the health checks done by the cluster members during leader elections (for example, to determine whether the leader is still running, or if there is a node which has a WAL position that is ahead of the one doing the query; etc.) The connect_address is put in the member key in DCS, making it possible to translate the member name into the address to connect to its REST API.
-
-        -  **listen**: IP address (or hostname) and port that Patroni will listen to for the REST API - to provide also the same health checks and cluster messaging between the participating nodes, as described above. to provide health-check information for HAProxy (or any other load balancer capable of doing a HTTP "OPTION" or "GET" checks).
-
-        -  **authentication**: (optional)
-            -  **username**: Basic-auth username to protect unsafe REST API endpoints.
-            -  **password**: Basic-auth password to protect unsafe REST API endpoints.
-        -  **certfile**: (optional): Specifies the file with the certificate in the PEM format. If the certfile is not specified or is left empty, the API server will work without SSL.
-        -  **keyfile**: (optional): Specifies the file with the secret key in the PEM format.
-        -  **keyfile\_password**: (optional): Specifies a password for decrypting the keyfile.
-        -  **cafile**: (optional): Specifies the file with the CA_BUNDLE with certificates of trusted CAs to use while verifying client certs.
-        -  **ciphers**: (optional): Specifies the permitted cipher suites (e.g. "ECDHE-RSA-AES256-GCM-SHA384:DHE-RSA-AES256-GCM-SHA384:ECDHE-RSA-AES128-GCM-SHA256:DHE-RSA-AES128-GCM-SHA256:!SSLv1:!SSLv2:!SSLv3:!TLSv1:!TLSv1.1")
-        -  **verify\_client**: (optional): ``none`` (default), ``optional`` or ``required``. When ``none`` REST API will not check client certificates. When ``required`` client certificates are required for all REST API calls. When ``optional`` client certificates are required for all unsafe REST API endpoints. When ``required`` is used, then client authentication succeeds, if the certificate signature verification succeeds.  For ``optional`` the client cert will only be checked for ``PUT``, ``POST``, ``PATCH``, and ``DELETE`` requests.
-        -  **allowlist**: (optional): Specifies the set of hosts that are allowed to call unsafe REST API endpoints. The single element could be a host name, an IP address or a network address using CIDR notation. By default ``allow all`` is used. In case if ``allowlist`` or ``allowlist_include_members`` are set, anything that is not included is rejected.
-        -  **allowlist\_include\_members**: (optional): If set to ``true`` it allows accessing unsafe REST API endpoints from other cluster members registered in DCS (IP address or hostname is taken from the members ``api_url``). Be careful, it might happen that OS will use a different IP for outgoing connections.
-        -  **http\_extra\_headers**: (optional): HTTP headers let the REST API server pass additional information with an HTTP response.
-        -  **https\_extra\_headers**: (optional): HTTPS headers let the REST API server pass additional information with an HTTP response when TLS is enabled. This will also pass additional information set in ``http_extra_headers``.
-
-Here is an example of both **http_extra_headers** and **https_extra_headers**:
-
-.. code:: YAML
-
-        restapi:
-          listen: <listen>
-          connect_address: <connect_address>
-          authentication:
-            username: <username>
-            password: <password>
-          http_extra_headers:
-            'X-Frame-Options': 'SAMEORIGIN'
-            'X-XSS-Protection': '1; mode=block'
-            'X-Content-Type-Options': 'nosniff'
-          cafile: <ca file>
-          certfile: <cert>
-          keyfile: <key>
-          https_extra_headers:
-            'Strict-Transport-Security': 'max-age=31536000; includeSubDomains'
-
-.. _patronictl_settings:
-
-CTL
----
-- **ctl**: (optional)
-    -  **insecure**: Allow connections to REST API without verifying SSL certs.
-    -  **cacert**: Specifies the file with the CA_BUNDLE file or directory with certificates of trusted CAs to use while verifying REST API SSL certs. If not provided patronictl will use the value provided for REST API "cafile" parameter.
-    -  **certfile**: Specifies the file with the client certificate in the PEM format. If not provided patronictl will use the value provided for REST API "certfile" parameter.
-    -  **keyfile**: Specifies the file with the client secret key in the PEM format. If not provided patronictl will use the value provided for REST API "keyfile" parameter.
-    -  **keyfile\_password**: Specifies a password for decrypting the keyfile. If not provided patronictl will use the value provided for REST API "keyfile\_password" parameter.
-
-Watchdog
---------
-- **mode**: ``off``, ``automatic`` or ``required``. When ``off`` watchdog is disabled. When ``automatic`` watchdog will be used if available, but ignored if it is not. When ``required`` the node will not become a leader unless watchdog can be successfully enabled.
-- **device**: Path to watchdog device. Defaults to ``/dev/watchdog``.
-- **safety_margin**: Number of seconds of safety margin between watchdog triggering and leader key expiration.
-
-.. _tags_settings:
-
-Tags
-----
-- **nofailover**: ``true`` or ``false``, controls whether this node is allowed to participate in the leader race and become a leader. Defaults to ``false``
-- **clonefrom**: ``true`` or ``false``. If set to ``true`` other nodes might prefer to use this node for bootstrap (take ``pg_basebackup`` from). If there are several nodes with ``clonefrom`` tag set to ``true`` the node to bootstrap from will be chosen randomly. The default value is ``false``.
-- **noloadbalance**: ``true`` or ``false``. If set to ``true`` the node will return HTTP Status Code 503 for the ``GET /replica`` REST API health-check and therefore will be excluded from the load-balancing. Defaults to ``false``.
-- **replicatefrom**: The IP address/hostname of another replica. Used to support cascading replication.
-- **nosync**: ``true`` or ``false``. If set to ``true`` the node will never be selected as a synchronous replica.
-
-In addition to these predefined tags, you can also add your own ones:
-
-- **key1**: ``true``
-- **key2**: ``false``
-- **key3**: ``1.4``
-- **key4**: ``"RandomString"``
-
-Tags are visible in the :ref:`REST API <rest_api>` and ``patronictl list`` You can also check for an instance health using these tags. If the tag isn't defined for an instance, or if the respective value doesn't match the querying value, it will return HTTP Status Code 503.

docs/conf.py

@@ -20,10 +20,15 @@
 import os
 
 import sys
+
 sys.path.insert(0, os.path.abspath('..'))
 
 from patroni.version import __version__
 
+project_root = os.path.abspath(os.path.join(os.path.dirname(__file__), '..'))
+module_dir = os.path.abspath(os.path.join(project_root, 'patroni'))
+excludes = ['tests', 'setup.py', 'conf']
+
 # -- General configuration ------------------------------------------------
 
 # If your documentation needs a minimal Sphinx version, state it here.
@@ -33,11 +38,21 @@ from patroni.version import __version__
 # Add any Sphinx extension module names here, as strings. They can be
 # extensions coming with Sphinx (named 'sphinx.ext.*') or your custom
 # ones.
-extensions = ['sphinx.ext.intersphinx',
+extensions = [
+    'sphinx.ext.intersphinx',
     'sphinx.ext.todo',
     'sphinx.ext.mathjax',
     'sphinx.ext.ifconfig',
-    'sphinx.ext.viewcode']
+    # 'sphinx.ext.viewcode',
+    'sphinx_github_style',  # Generate "View on GitHub" for source code
+    'sphinxcontrib.apidoc',  # For generating module docs from code
+    'sphinx.ext.autodoc',  # For generating module docs from docstrings
+    'sphinx.ext.napoleon',  # For Google and Numpy formatted docstrings
+]
+apidoc_module_dir = module_dir
+apidoc_output_dir = 'modules'
+apidoc_excluded_paths = excludes
+apidoc_separate_modules = True
 
 # Add any paths that contain templates here, relative to this directory.
 templates_path = ['_templates']
@@ -70,7 +85,7 @@ release = __version__
 #
 # This is also used if you do content translation via gettext catalogs.
 # Usually you set "language" from the command line for these cases.
-language = None
+language = 'en'
 
 # List of patterns, relative to source directory, that match files and
 # directories to ignore when looking for source files.
@@ -90,10 +105,10 @@ todo_include_todos = True
 # a list of builtin themes.
 #
 
+html_theme = 'sphinx_rtd_theme'
 on_rtd = os.environ.get('READTHEDOCS', None) == 'True'
 if not on_rtd:  # only import and set the theme if we're building docs locally
     import sphinx_rtd_theme
-    html_theme = 'sphinx_rtd_theme'
     html_theme_path = [sphinx_rtd_theme.get_html_theme_path()]
 
 # Theme options are theme-specific and customize the look and feel of a theme
@@ -107,6 +122,34 @@ if not on_rtd:  # only import and set the theme if we're building docs locally
 # so a file named "default.css" will overwrite the builtin "default.css".
 html_static_path = ['_static']
 
+# Replace "source" links with "edit on GitHub" when using rtd theme
+html_context = {
+    'display_github': True,
+    'github_user': 'zalando',
+    'github_repo': 'patroni',
+    'github_version': 'master',
+    'conf_py_path': '/docs/',
+}
+
+# sphinx-github-style options, https://sphinx-github-style.readthedocs.io/en/latest/index.html
+
+# The name of the top-level package.
+top_level = "patroni"
+
+# The blob to link to on GitHub - any of "head", "last_tag", or "{blob}"
+# linkcode_blob = 'head'
+
+# The link to your GitHub repository formatted as https://github.com/user/repo
+# If not provided, will attempt to create the link from the html_context dict
+# linkcode_url = f"https://github.com/{html_context['github_user']}/" \
+#                f"{html_context['github_repo']}/{html_context['github_version']}"
+
+# The text to use for the linkcode link
+# linkcode_link_text: str = "View on GitHub"
+
+# A linkcode_resolve() function to use for resolving the link target
+# linkcode_resolve: types.FunctionType
+
 
 # -- Options for HTMLHelp output ------------------------------------------
 
@@ -165,7 +208,6 @@ texinfo_documents = [
 ]
 
 
-
 # -- Options for Epub output ----------------------------------------------
 
 # Bibliographic Dublin Core info.
@@ -187,9 +229,56 @@ epub_copyright = copyright
 epub_exclude_files = ['search.html']
 
 
-
 # Example configuration for intersphinx: refer to the Python standard library.
-intersphinx_mapping = {'https://docs.python.org/': None}
+intersphinx_mapping = {'python': ('https://docs.python.org/', None)}
+
+
+# Remove these pages from index, references, toc trees, etc.
+# If the builder is not 'html' then add the API docs modules index to pages to be removed.
+exclude_from_builder = {
+    'latex': ['modules/modules'],
+    'epub': ['modules/modules'],
+}
+# Internal holding list, anything added here will always be excluded
+_docs_to_remove = []
+
+
+def builder_inited(app):
+    """Run during Sphinx `builder-inited` phase.
+
+    Set a config value to builder name and add module docs to `docs_to_remove`.
+    """
+    print(f'The builder is: {app.builder.name}')
+    app.add_config_value('builder', app.builder.name, 'env')
+
+    # Remove pages when builder matches any referenced in exclude_from_builder
+    if exclude_from_builder.get(app.builder.name):
+        _docs_to_remove.extend(exclude_from_builder[app.builder.name])
+
+
+def env_get_outdated(app, env, added, changed, removed):
+    """Run during Sphinx `env-get-outdated` phase.
+
+    Remove the items listed in `docs_to_remove` from known pages.
+    """
+    added.difference_update(_docs_to_remove)
+    changed.difference_update(_docs_to_remove)
+    removed.update(_docs_to_remove)
+    return []
+
+
+def doctree_read(app, doctree):
+    """Run during Sphinx `doctree-read` phase.
+
+    Remove the items listed in `docs_to_remove` from the table of contents.
+    """
+    from sphinx import addnodes
+    for toc_tree_node in doctree.traverse(addnodes.toctree):
+        for e in toc_tree_node['entries']:
+            ref = str(e[1])
+            if ref in _docs_to_remove:
+                toc_tree_node['entries'].remove(e)
+
 
 # A possibility to have an own stylesheet, to add new rules or override existing ones
 # For the latter case, the CSS specificity of the rules should be higher than the default ones
@@ -198,3 +287,8 @@ def setup(app):
         app.add_css_file('custom.css')
     else:
         app.add_stylesheet('custom.css')
+
+    # Run extra steps to remove module docs when running with a non-html builder
+    app.connect('builder-inited', builder_inited)
+    app.connect('env-get-outdated', env_get_outdated)
+    app.connect('doctree-read', doctree_read)

docs/contributing_guidelines.rst

@@ -0,0 +1,182 @@
+.. _contributing_guidelines:
+
+Contributing guidelines
+=======================
+
+Wanna contribute to Patroni? Yay - here is how!
+
+Chatting
+--------
+
+Just want to chat with other Patroni users?  Looking for interactive troubleshooting help? Join us on channel `#patroni <https://postgresteam.slack.com/archives/C9XPYG92A>`__ in the `PostgreSQL Slack <https://pgtreats.info/slack-invite>`__.
+
+Running tests
+-------------
+
+Requirements for running behave tests:
+
+1. PostgreSQL packages need to be installed.
+2. PostgreSQL binaries must be available in your `PATH`. You may need to add them to the path with something like `PATH=/usr/lib/postgresql/11/bin:$PATH python -m behave`.
+3. If you'd like to test with external DCSs (e.g., Etcd, Consul, and Zookeeper) you'll need the packages installed and respective services running and accepting unencrypted/unprotected connections on localhost and default port. In the case of Etcd or Consul, the behave test suite could start them up if binaries are available in the `PATH`.
+
+Install dependencies:
+
+.. code-block:: bash
+
+    # You may want to use Virtualenv or specify pip3.
+    pip install -r requirements.txt
+    pip install -r requirements.dev.txt
+
+After you have all dependencies installed, you can run the various test suites:
+
+.. code-block:: bash
+
+    # You may want to use Virtualenv or specify python3.
+
+    # Run flake8 to check syntax and formatting:
+    python setup.py flake8
+
+    # Run the pytest suite in tests/:
+    python setup.py test
+
+    # Run the behave (https://behave.readthedocs.io/en/latest/) test suite in features/;
+    # modify DCS as desired (raft has no dependencies so is the easiest to start with):
+    DCS=raft python -m behave
+
+Testing with tox
+----------------
+
+To run tox tests you only need to install one dependency (other than Python)
+
+.. code-block:: bash
+
+    pip install tox>=4
+
+If you wish to run `behave` tests then you also need docker installed.
+
+Tox configuration in `tox.ini` has "environments" to run the following tasks:
+
+* lint: Python code lint with `flake8`
+* test: unit tests for all available python interpreters with `pytest`,
+  generates XML reports or HTML reports if a TTY is detected
+* dep: detect package dependency conflicts using `pipdeptree`
+* type: static type checking with `pyright`
+* black: code formatting with `black`
+* docker-build: build docker image used for the `behave` env
+* docker-cmd: run arbitrary command with the above image
+* docker-behave-etcd: run tox for behave tests with above image
+* py*behave: run behave with available python interpreters (without docker, although
+  this is what is called inside docker containers)
+* docs: build docs with `sphinx`
+
+Running tox
+^^^^^^^^^^^
+
+To run the default env list; dep, lint, test, and docs, just run:
+
+.. code-block:: bash
+
+    tox
+
+The `test` envs can be run with the label `test`:
+
+.. code-block:: bash
+
+   tox -m test
+
+The `behave` docker tests can be run with the label `behave`:
+
+.. code-block:: bash
+
+   tox -m behave
+
+Similarly, docs has the label `docs`.
+
+All other envs can be run with their respective env names:
+
+.. code-block:: bash
+
+   tox -e lint
+   tox -e py39-test-lin
+
+It is also possible to select partial env lists using `factors`. For example, if you want to run
+all envs for python 3.10:
+
+.. code-block:: bash
+
+    tox -f py310
+
+This is equivalent to running all the envs listed below:
+
+.. code-block:: bash
+
+    $ tox -l -f py310
+    py310-test-lin
+    py310-test-mac
+    py310-test-win
+    py310-type-lin
+    py310-type-mac
+    py310-type-win
+    py310-behave-etcd-lin
+    py310-behave-etcd-win
+    py310-behave-etcd-mac
+
+
+You can list all configured combinations of environments with tox (>=v4) like so
+
+.. code-block:: bash
+
+    tox l
+
+The envs `test` and `docs` will attempt to open the HTML output files
+when the job completes, if tox is run with an active terminal. This
+is intended to be for benefit of the developer running this env locally.
+It will attempt to run `open` on a mac and `xdg-open` on Linux.
+To use a different command set the env var `OPEN_CMD` to the name or path of
+the command. If this step fails it will not fail the run overall.
+If you want to disable this facility set the env var `OPEN_CMD` to the `:` no-op command.
+
+.. code-block:: bash
+
+   OPEN_CMD=: tox -m docs
+
+Behave tests
+^^^^^^^^^^^^
+
+Behave tests with `-m behave` will build docker images based on PG_MAJOR version 11 through 15 and then run all
+behave tests. This can take quite a long time to run so you might want to limit the scope to a select version of
+Postgres or to a specific feature set or steps.
+
+To specify the version of postgres include the full name of the dependent image build env that you want and then the
+behave env name. For instance if you want Postgres 15 use:
+
+.. code-block:: bash
+
+    tox -e pg14-docker-build,pg14-docker-behave-etcd-lin
+
+If on the other hand you want to test a specific feature you can pass positional arguments to behave. This will run
+the watchdog behave feature test scenario with all versions of Postgres.
+
+.. code-block:: bash
+
+    tox -m behave -- features/watchdog.feature
+
+Of course you can combine the two.
+
+Reporting issues
+----------------
+
+If you have a question about patroni or have a problem using it, please read the :ref:`README <readme>` before filing an issue.
+Also double check with the current issues on our `Issues Tracker <https://github.com/zalando/patroni/issues>`__.
+
+Contributing a pull request
+---------------------------
+
+1) Submit a comment to the relevant issue or create a new issue describing your proposed change.
+2) Do a fork, develop and test your code changes.
+3) Include documentation
+4) Submit a pull request.
+
+You'll get feedback about your pull request as soon as possible.
+
+Happy Patroni hacking ;-)

docs/dcs_failsafe_mode.rst

@@ -23,7 +23,7 @@ In general, it is impossible to distinguish between these two from a single node
 DCS Failsafe Mode
 -----------------
 
-We introduce a new special option, the ``failsafe_mode``. It could be enabled only via global configuration stored in the DCS ``/config`` key. If the failsafe mode is enabled and the leader lock update in DCS failed due to reasons different from the version/value/index mismatch, Postgres may continue to run as a primary if it can access all known members of the cluster via Patroni REST API.
+We introduce a new special option, the ``failsafe_mode``. It could be enabled only via global :ref:`dynamic configuration <dynamic_configuration>` stored in the DCS ``/config`` key. If the failsafe mode is enabled and the leader lock update in DCS failed due to reasons different from the version/value/index mismatch, Postgres may continue to run as a primary if it can access all known members of the cluster via Patroni REST API.
 
 
 Low-level implementation details
@@ -53,7 +53,7 @@ F.A.Q.
 - What if all members of the Patroni cluster are lost while DCS is down?
 
   Patroni could be configured to create the new replica from the backup even when the cluster doesn't have a leader. But, if the new member isn't present in the ``/failsafe`` key, it will not be able to grab the leader lock and promote.
-  
+
 - What will happen if the primary lost access to DCS while replicas didn't?
 
   The primary will execute the failsafe code and contact all known replicas. These replicas will use this information as an indicator that the primary is alive and will not start the leader race even if the leader lock in DCS has expired.

docs/dynamic_configuration.rst

@@ -1,89 +1,83 @@
 .. _dynamic_configuration:
 
-Patroni configuration
-=====================
+==============================
+Dynamic Configuration Settings
+==============================
 
-Patroni configuration is stored in the DCS (Distributed Configuration Store). There are 3 types of configuration:
+Dynamic configuration is stored in the DCS (Distributed Configuration Store) and applied on all cluster nodes.
 
-- Dynamic configuration.
-	These options can be set in DCS at any time. If the options changed are not part of the startup configuration,
-	they are applied asynchronously (upon the next wake up cycle) to every node, which gets subsequently reloaded.
-	If the node requires a restart to apply the configuration (for options with context postmaster, if their values
-	have changed), a special flag, ``pending_restart`` indicating this, is set in the members.data JSON.
-	Additionally, the node status also indicates this, by showing ``"restart_pending": true``.
+In order to change the dynamic configuration you can use either ``patronictl edit-config`` tool or Patroni :ref:`REST API <rest_api>`.
 
-- Local :ref:`configuration <settings>` (patroni.yml).
-	These options are defined in the configuration file and take precedence over dynamic configuration.
-	patroni.yml could be changed and reloaded in runtime (without restart of Patroni) by sending SIGHUP to the Patroni process, performing ``POST /reload`` REST-API request or executing ``patronictl reload``.
+-  **loop\_wait**: the number of seconds the loop will sleep. Default value: 10
+-  **ttl**: the TTL to acquire the leader lock (in seconds). Think of it as the length of time before initiation of the automatic failover process. Default value: 30
+-  **retry\_timeout**: timeout for DCS and PostgreSQL operation retries (in seconds). DCS or network issues shorter than this will not cause Patroni to demote the leader. Default value: 10
+-  **maximum\_lag\_on\_failover**: the maximum bytes a follower may lag to be able to participate in leader election.
+-  **maximum\_lag\_on\_syncnode**: the maximum bytes a synchronous follower may lag before it is considered as an unhealthy candidate and swapped by healthy asynchronous follower. Patroni utilize the max replica lsn if there is more than one follower, otherwise it will use leader's current wal lsn. Default is -1, Patroni will not take action to swap synchronous unhealthy follower when the value is set to 0 or below. Please set the value high enough so Patroni won't swap synchrounous follower fequently during high transaction volume.
+-  **max\_timelines\_history**: maximum number of timeline history items kept in DCS.  Default value: 0. When set to 0, it keeps the full history in DCS.
+-  **primary\_start\_timeout**: the amount of time a primary is allowed to recover from failures before failover is triggered (in seconds). Default is 300 seconds. When set to 0 failover is done immediately after a crash is detected if possible. When using asynchronous replication a failover can cause lost transactions. Worst case failover time for primary failure is: loop\_wait + primary\_start\_timeout + loop\_wait, unless primary\_start\_timeout is zero, in which case it's just loop\_wait. Set the value according to your durability/availability tradeoff.
+-  **primary\_stop\_timeout**: The number of seconds Patroni is allowed to wait when stopping Postgres and effective only when synchronous_mode is enabled. When set to > 0 and the synchronous_mode is enabled, Patroni sends SIGKILL to the postmaster if the stop operation is running for more than the value set by primary\_stop\_timeout. Set the value according to your durability/availability tradeoff. If the parameter is not set or set <= 0, primary\_stop\_timeout does not apply.
+-  **synchronous\_mode**: turns on synchronous replication mode. In this mode a replica will be chosen as synchronous and only the latest leader and synchronous replica are able to participate in leader election. Synchronous mode makes sure that successfully committed transactions will not be lost at failover, at the cost of losing availability for writes when Patroni cannot ensure transaction durability. See :ref:`replication modes documentation <replication_modes>` for details.
+-  **synchronous\_mode\_strict**: prevents disabling synchronous replication if no synchronous replicas are available, blocking all client writes to the primary. See :ref:`replication modes documentation <replication_modes>` for details.
+-  **failsafe\_mode**: Enables :ref:`DCS Failsafe Mode <dcs_failsafe_mode>`. Defaults to `false`.
+-  **postgresql**:
 
-- Environment :ref:`configuration <environment>`.
-	It is possible to set/override some of the "Local" configuration parameters with environment variables.
-	Environment configuration is very useful when you are running in a dynamic environment and you don't know some of the parameters in advance (for example it's not possible to know your external IP address when you are running inside ``docker``).
+   -  **use\_pg\_rewind**: whether or not to use pg_rewind. Defaults to `false`.
+   -  **use\_slots**: whether or not to use replication slots. Defaults to `true` on PostgreSQL 9.4+.
+   -  **recovery\_conf**: additional configuration settings written to recovery.conf when configuring follower. There is no recovery.conf anymore in PostgreSQL 12, but you may continue using this section, because Patroni handles it transparently.
+   -  **parameters**: list of configuration settings for Postgres.
 
-The local configuration can be either a single YAML file or a directory. When it is a directory, all YAML files in that directory are loaded one by one in sorted order. In case a key is defined in multiple files, the occurrence in the last file takes precedence.
+   -  **pg\_hba**: list of lines that Patroni will use to generate ``pg_hba.conf``. Patroni ignores this parameter if ``hba_file`` PostgreSQL parameter is set to a non-default value.
 
-Some of the PostgreSQL parameters must hold the same values on the primary and the replicas. For those, values set either in the local patroni configuration files or via the environment variables take no effect. To alter or set their values one must change the shared configuration in the DCS. Below is the actual list of such parameters together with the default values:
+      -  **- host all all 0.0.0.0/0 md5**
+      -  **- host replication replicator 127.0.0.1/32 md5**: A line like this is required for replication.
 
-- max_connections: 100
-- max_locks_per_transaction: 64
-- max_worker_processes: 8
-- max_prepared_transactions: 0
-- wal_level: hot_standby
-- wal_log_hints: on
-- track_commit_timestamp: off
+   -  **pg\_ident**: list of lines that Patroni will use to generate ``pg_ident.conf``. Patroni ignores this parameter if ``ident_file`` PostgreSQL parameter is set to a non-default value.
 
-For the parameters below, PostgreSQL does not require equal values among the primary and all the replicas. However, considering the possibility of a replica to become the primary at any time, it doesn't really make sense to set them differently; therefore, Patroni restricts setting their values to the Dynamic configuration
+      -  **- mapname1 systemname1 pguser1**
+      -  **- mapname1 systemname2 pguser2**
 
-- max_wal_senders: 5
-- max_replication_slots: 5
-- wal_keep_segments: 8
-- wal_keep_size: 128MB
+-  **standby\_cluster**: if this section is defined, we want to bootstrap a standby cluster.
 
-These parameters are validated to ensure they are sane, or meet a minimum value.
+   -  **host**: an address of remote node
+   -  **port**: a port of remote node
+   -  **primary\_slot\_name**: which slot on the remote node to use for replication. This parameter is optional, the default value is derived from the instance name (see function `slot_name_from_member_name`).
+   -  **create\_replica\_methods**: an ordered list of methods that can be used to bootstrap standby leader from the remote primary, can be different from the list defined in :ref:`postgresql_settings`
+   -  **restore\_command**: command to restore WAL records from the remote primary to nodes in a standby cluster, can be different from the list defined in :ref:`postgresql_settings`
+   -  **archive\_cleanup\_command**: cleanup command for standby leader
+   -  **recovery\_min\_apply\_delay**: how long to wait before actually apply WAL records on a standby leader
 
-There are some other Postgres parameters controlled by Patroni:
+-  **slots**: define permanent replication slots. These slots will be preserved during switchover/failover. Permanent slots that don't exist will be created by Patroni. The physical slots are maintained only in the current primary. The logical slots are copied from the primary to a standby with restart, and after that their position advanced every **loop_wait** seconds (if necessary). Copying logical slot files performed via ``libpq`` connection and using either rewind or superuser credentials (see **postgresql.authentication** section). There is always a chance that the logical slot position on the replica is a bit behind the former primary, therefore application should be prepared that some messages could be received the second time after the failover. The easiest way of doing so - tracking ``confirmed_flush_lsn``. Enabling permanent logical replication slots requires **postgresql.use_slots** to be set and will also automatically enable the ``hot_standby_feedback``. Since the failover of logical replication slots is unsafe on PostgreSQL 9.6 and older and PostgreSQL version 10 is missing some important functions, the feature only works with PostgreSQL 11+.
 
-- listen_addresses - is set either from ``postgresql.listen`` or from ``PATRONI_POSTGRESQL_LISTEN`` environment variable
-- port - is set either from ``postgresql.listen`` or from ``PATRONI_POSTGRESQL_LISTEN`` environment variable
-- cluster_name - is set either from ``scope`` or from ``PATRONI_SCOPE`` environment variable
-- hot_standby: on
+   -  **my\_slot\_name**: the name of the permanent replication slot. If the permanent slot name matches with the name of the current leader it will not be created. Please note that Patroni does not make checks for permanent slot names added to this configuration matching those that Patroni creates automatically for members. If those names are added, Patroni will ensure that any slots that were created are not removed even if the member becomes unresponsive, situation which would normally result in the slot's removal by Patroni. Although this can be useful in some situations, such as when importing existing members to a new Patroni cluster (see :ref:`Convert a Standalone to a Patroni Cluster <existing_data>` for details), caution should be exercised by the operator that these clashes in names are not persisted in the DCS due to its effect on normal functioning of Patroni.
 
-To be on the safe side parameters from the above lists are not written into ``postgresql.conf``, but passed as a list of arguments to the ``pg_ctl start`` which gives them the highest precedence, even above `ALTER SYSTEM <https://www.postgresql.org/docs/current/static/sql-altersystem.html>`__
+      -  **type**: slot type. Could be ``physical`` or ``logical``. If the slot is logical, you have to additionally define ``database`` and ``plugin``.
+      -  **database**: the database name where logical slots should be created.
+      -  **plugin**: the plugin name for the logical slot.
 
+-  **ignore\_slots**: list of sets of replication slot properties for which Patroni should ignore matching slots. This configuration/feature/etc. is useful when some replication slots are managed outside of Patroni. Any subset of matching properties will cause a slot to be ignored.
 
-When applying the local or dynamic configuration options, the following actions are taken:
+   -  **name**: the name of the replication slot.
+   -  **type**: slot type. Can be ``physical`` or ``logical``. If the slot is logical, you may additionally define ``database`` and/or ``plugin``.
+   -  **database**: the database name (when matching a ``logical`` slot).
+   -  **plugin**: the logical decoding plugin (when matching a ``logical`` slot).
 
-- The node first checks if there is a postgresql.base.conf or if the ``custom_conf`` parameter is set.
-- If the `custom_conf` parameter is set, it will take the file specified on it as a base configuration, ignoring `postgresql.base.conf` and `postgresql.conf`.
-- If the `custom_conf` parameter is not set and `postgresql.base.conf` exists, it contains the renamed "original" configuration and it will be used as a base configuration.
-- If there is no `custom_conf` nor `postgresql.base.conf`, the original postgresql.conf is taken and renamed to postgresql.base.conf.
-- The dynamic options (with the exceptions above) are dumped into the postgresql.conf and an include is set in
-  postgresql.conf to the used base configuration (either postgresql.base.conf or what is on ``custom_conf``). Therefore, we would be able to apply new options without re-reading the configuration file to check if the include is present not.
-- Some parameters that are essential for Patroni to manage the cluster are overridden using the command line.
-- If some of the options that require restart are changed (we should look at the context in pg_settings and at the actual
-  values of those options), a pending_restart flag of a given node is set. This flag is reset on any restart.
+Note: **slots** is a hashmap while **ignore_slots** is an array. For example:
 
-The parameters would be applied in the following order (run-time are given the highest priority):
+.. code:: YAML
 
-1. load parameters from file `postgresql.base.conf` (or from a `custom_conf` file, if set)
-2. load parameters from file `postgresql.conf`
-3. load parameters from file `postgresql.auto.conf`
-4. run-time parameter using `-o --name=value`
-
-This allows configuration for all the nodes (2), configuration for a specific node using `ALTER SYSTEM` (3) and ensures that parameters essential to the running of Patroni are enforced (4), as well as leaves room for configuration tools that manage `postgresql.conf` directly without involving Patroni (1).
-
-
-Also, the following Patroni configuration options can be changed only dynamically:
-
-- ttl: 30
-- loop_wait: 10
-- retry_timeouts: 10
-- maximum_lag_on_failover: 1048576
-- max_timelines_history: 0
-- check_timeline: false
-- postgresql.use_slots: true
-
-Upon changing these options, Patroni will read the relevant section of the configuration stored in DCS and change its
-run-time values.
-
-Patroni nodes are dumping the state of the DCS options to disk upon for every change of the configuration into the file ``patroni.dynamic.json`` located in the Postgres data directory. Only the leader is allowed to restore these options from the on-disk dump if these are completely absent from the DCS or if they are invalid.
+        slots:
+          permanent_logical_slot_name:
+            type: logical
+            database: my_db
+            plugin: test_decoding
+          permanent_physical_slot_name:
+            type: physical
+          ...
+        ignore_slots:
+          - name: ignored_logical_slot_name
+            type: logical
+            database: my_db
+            plugin: test_decoding
+          - name: ignored_physical_slot_name
+            type: physical
+          ...

docs/existing_data.rst

@@ -10,18 +10,58 @@ To deploy a Patroni cluster without using a pre-existing PostgreSQL instance, se
 Procedure
 ---------
 
-A Patroni cluster can be started with a data directory from a single-node PostgreSQL database. This is achieved by following closely these steps:
+You can find below an overview of steps for converting an existing Postgres cluster to a Patroni managed cluster. In the steps we assume all nodes that are part of the existing cluster are currently up and running, and that you *do not* intend to change Postgres configuration while the migration is ongoing. The steps:
 
-1. Manually start PostgreSQL daemon
-2. Create Patroni superuser and replication users as defined in the :ref:`authentication <postgresql_settings>` section of the Patroni configuration. If this user is created in SQL, the following queries achieve this:
+#. Create the Postgres users as explained for :ref:`authentication <postgresql_settings>` section of the Patroni configuration. You can find sample SQL commands to create the users in the code block below, in which you need to replace the usernames and passwords as per your environment. If you already have the relevant users, then you can skip this step.
 
-.. code-block:: sql
+   .. code-block:: sql
 
-   CREATE USER $PATRONI_SUPERUSER_USERNAME WITH SUPERUSER ENCRYPTED PASSWORD '$PATRONI_SUPERUSER_PASSWORD';
-   CREATE USER $PATRONI_REPLICATION_USERNAME WITH REPLICATION ENCRYPTED PASSWORD '$PATRONI_REPLICATION_PASSWORD';
+      -- Patroni superuser
+      -- Replace PATRONI_SUPERUSER_USERNAME and PATRONI_SUPERUSER_PASSWORD accordingly
+      CREATE USER PATRONI_SUPERUSER_USERNAME WITH SUPERUSER ENCRYPTED PASSWORD 'PATRONI_SUPERUSER_PASSWORD';
 
-3. Start Patroni (e.g. ``patroni /etc/patroni/patroni.yml``). It automatically detects that PostgreSQL daemon is already running but its configuration might be out-of-date.
-4. Ask Patroni to restart the node with ``patronictl restart cluster-name node-name``. This step is only required if PostgreSQL configuration is out-of-date.
+      -- Patroni replication user
+      -- Replace PATRONI_REPLICATION_USERNAME and PATRONI_REPLICATION_PASSWORD accordingly
+      CREATE USER PATRONI_REPLICATION_USERNAME WITH REPLICATION ENCRYPTED PASSWORD 'PATRONI_REPLICATION_PASSWORD';
+
+      -- Patroni rewind user, if you intend to enable use_pg_rewind in your Patroni configuration
+      -- Replace PATRONI_REWIND_USERNAME and PATRONI_REWIND_PASSWORD accordingly
+      CREATE USER PATRONI_REWIND_USERNAME WITH ENCRYPTED PASSWORD 'PATRONI_REWIND_PASSWORD';
+      GRANT EXECUTE ON function pg_catalog.pg_ls_dir(text, boolean, boolean) TO PATRONI_REWIND_USERNAME;
+      GRANT EXECUTE ON function pg_catalog.pg_stat_file(text, boolean) TO PATRONI_REWIND_USERNAME;
+      GRANT EXECUTE ON function pg_catalog.pg_read_binary_file(text) TO PATRONI_REWIND_USERNAME;
+      GRANT EXECUTE ON function pg_catalog.pg_read_binary_file(text, bigint, bigint, boolean) TO PATRONI_REWIND_USERNAME;
+
+#. Perform the following steps on all Postgres nodes. Perform all steps on one node before proceeding with the next node. Start with the primary node, then proceed with each standby node:
+
+   #. If you are running Postgres through systemd, then disable the Postgres systemd unit. This is performed as Patroni manages starting and stopping the Postgres daemon.
+
+   #. Create a YAML configuration file for Patroni.
+
+      * **Note (specific for the primary node):** If you have replication slots being used for replication between cluster members, then it is recommended that you enable ``use_slots`` and configure the existing replication slots as permanent via the ``slots`` configuration item. Be aware that Patroni automatically creates replication slots for replication between members, and drops replication slots that it does not recognize, when ``use_slots`` is enabled. The idea of using permanent slots here is to allow your existing slots to persist while the migration to Patroni is in progress. See :ref:`YAML Configuration Settings <yaml_configuration>` for details.
+
+   #. Start Patroni using the ``patroni`` systemd service unit. It automatically detects that Postgres is already running and starts monitoring the instance.
+
+#. Hand over Postgres "start up procedure" to Patroni. In order to do that you need to restart the cluster members through ``patronictl restart cluster-name member-name`` command. For minimal downtime you might want to split this step into:
+
+   #. Immediate restart of the standby nodes.
+   #. Scheduled restart of the primary node within a maintenance window.
+
+#. If you configured permanent slots in step ``1.2.``, then you should remove them from ``slots`` configuration through ``patronictl edit-config cluster-name member-name`` command once the ``restart_lsn`` of the slots created by Patroni is able to catch up with the ``restart_lsn`` of the original slots for the corresponding members. By removing the slots from ``slots`` configuration you will allow Patroni to drop the original slots from your cluster once they are not needed anymore. You can find below an example query to check the ``restart_lsn`` of a couple slots, so you can compare them:
+
+   .. code-block:: sql
+
+      -- Assume original_slot_for_member_x is the name of the slot in your original
+      -- cluster for replicating changes to member X, and slot_for_member_x is the
+      -- slot created by Patroni for that purpose. You need restart_lsn of
+      -- slot_for_member_x to be >= restart_lsn of original_slot_for_member_x
+      SELECT slot_name,
+             restart_lsn
+      FROM pg_replication_slots
+      WHERE slot_name IN (
+          'original_slot_for_member_x',
+          'slot_for_member_x'
+      )
 
 .. _major_upgrade:
 
@@ -30,14 +70,14 @@ Major Upgrade of PostgreSQL Version
 
 The only possible way to do a major upgrade currently is:
 
-1. Stop Patroni
-2. Upgrade PostgreSQL binaries and perform `pg_upgrade <https://www.postgresql.org/docs/current/pgupgrade.html>`_ on the primary node
-3. Update patroni.yml
-4. Remove the initialize key from DCS or wipe complete cluster state from DCS. The second one could be achieved by running ``patronictl remove <cluster-name>``. It is necessary because pg_upgrade runs initdb which actually creates a new database with a new PostgreSQL system identifier.
-5. If you wiped the cluster state in the previous step, you may wish to copy patroni.dynamic.json from old data dir to the new one.  It will help you to retain some PostgreSQL parameters you had set before.
-6. Start Patroni on the primary node.
-7. Upgrade PostgreSQL binaries, update patroni.yml and wipe the data_dir on standby nodes.
-8. Start Patroni on the standby nodes and wait for the replication to complete.
+#. Stop Patroni
+#. Upgrade PostgreSQL binaries and perform `pg_upgrade <https://www.postgresql.org/docs/current/pgupgrade.html>`_ on the primary node
+#. Update patroni.yml
+#. Remove the initialize key from DCS or wipe complete cluster state from DCS. The second one could be achieved by running ``patronictl remove <cluster-name>``. It is necessary because pg_upgrade runs initdb which actually creates a new database with a new PostgreSQL system identifier.
+#. If you wiped the cluster state in the previous step, you may wish to copy patroni.dynamic.json from old data dir to the new one.  It will help you to retain some PostgreSQL parameters you had set before.
+#. Start Patroni on the primary node.
+#. Upgrade PostgreSQL binaries, update patroni.yml and wipe the data_dir on standby nodes.
+#. Start Patroni on the standby nodes and wait for the replication to complete.
 
 Running pg_upgrade on standby nodes is not supported by PostgreSQL. If you know what you are doing, you can try the rsync procedure described in https://www.postgresql.org/docs/current/pgupgrade.html instead of wiping data_dir on standby nodes. The safest way is however to let Patroni replicate the data for you.
 

docs/ha_multi_dc.rst

@@ -1,8 +1,8 @@
 .. _ha_multi_dc:
 
-=================
+===================
 HA multi datacenter
-=================
+===================
 
 The high availability of a PostgreSQL cluster deployed in multiple data centers is based on replication, which can be synchronous or asynchronous (`replication_modes <replication_modes.rst>`_).
 
@@ -12,7 +12,7 @@ In both cases, it is important to be clear about the following concepts:
 - You should run the odd number of etcd, ZooKeeper or Consul nodes: 3 or 5!
 
 Synchronous Replication
-----------------------------
+-----------------------
 
 To have a multi DC cluster that can automatically tolerate a zone drop, a minimum of 3 is required.
 
@@ -22,12 +22,12 @@ The architecture diagram would be the following:
 
 We must deploy a cluster of etcd, ZooKeeper or Consul through the different DC, with a minimum of 3 nodes, one in each zone.
 
-Regarding postgres, we must deploy at least 2 nodes, in different DC. Then you have to set ``synchronous_mode: true`` in the global configuration (``patronictl edit-config``).
+Regarding postgres, we must deploy at least 2 nodes, in different DC. Then you have to set ``synchronous_mode: true`` in the global :ref:`dynamic configuration <dynamic_configuration>`.
 
 This enables sync replication and the primary node will choose one of the nodes as synchronous.
 
 Asynchronous Replication
-----------------------------------
+------------------------
 
 With only two data centers it would be better to have two independent etcd clusters and run Patroni :ref:`standby cluster <standby_cluster>` in the second data center. If the first site is down, you can MANUALLY promote the ``standby_cluster``.
 
@@ -37,7 +37,7 @@ The architecture diagram would be the following:
 
 Automatic promotion is not possible, because DC2 will never able to figure out the state of DC1.
 
-You should not use ``pg_ctl promote`` in this scenario, you need "manually promote" the healthy cluster with ``patronictl edit-config`` and remove ``standby_cluster`` section from there.
+You should not use ``pg_ctl promote`` in this scenario, you need "manually promote" the healthy cluster by removing ``standby_cluster`` section from the :ref:`dynamic configuration <dynamic_configuration>`.
 
 .. warning::
     If the source cluster is still up and running and you promote the standby cluster you create a split-brain.

docs/index.rst

@@ -6,11 +6,11 @@
 Introduction
 ============
 
-Patroni is a template for you to create your own customized, high-availability solution using Python and - for maximum accessibility - a distributed configuration store like `ZooKeeper <https://zookeeper.apache.org/>`__, `etcd <https://github.com/coreos/etcd>`__, `Consul <https://github.com/hashicorp/consul>`__ or `Kubernetes <https://kubernetes.io>`__. Database engineers, DBAs, DevOps engineers, and SREs who are looking to quickly deploy HA PostgreSQL in the datacenter-or anywhere else-will hopefully find it useful.
+Patroni is a template for high availability (HA) PostgreSQL solutions using Python. For maximum accessibility, Patroni supports a variety of distributed configuration stores like `ZooKeeper <https://zookeeper.apache.org/>`__, `etcd <https://github.com/coreos/etcd>`__, `Consul <https://github.com/hashicorp/consul>`__ or `Kubernetes <https://kubernetes.io>`__. Database engineers, DBAs, DevOps engineers, and SREs who are looking to quickly deploy HA PostgreSQL in datacenters — or anywhere else — will hopefully find it useful.
 
 We call Patroni a "template" because it is far from being a one-size-fits-all or plug-and-play replication system. It will have its own caveats. Use wisely. There are many ways to run high availability with PostgreSQL; for a list, see the `PostgreSQL Documentation <https://wiki.postgresql.org/wiki/Replication,_Clustering,_and_Connection_Pooling>`__.
 
-Currently supported PostgreSQL versions: 9.3 to 15.
+Currently supported PostgreSQL versions: 9.3 to 16.
 
 **Note to Citus users**: Starting from 3.0 Patroni nicely integrates with the `Citus <https://github.com/citusdata/citus>`__ database extension to Postgres. Please check the :ref:`Citus support page <citus>` in the Patroni documentation for more info about how to use Patroni high availability together with a Citus distributed cluster.
 
@@ -22,26 +22,31 @@ Currently supported PostgreSQL versions: 9.3 to 15.
    :caption: Contents:
 
    README
-   citus
-   dynamic_configuration
-   dcs_failsafe_mode
+   patroni_configuration
    rest_api
-   existing_data
-   ENVIRONMENT
-   SETTINGS
-   security
    replica_bootstrap
    replication_modes
-   ha_multi_dc
-   pause
-   kubernetes
    watchdog
+   pause
+   dcs_failsafe_mode
+   kubernetes
+   citus
+   existing_data
+   security
+   ha_multi_dc
    releases
    CONTRIBUTING
 
 Indices and tables
 ==================
 
-* :ref:`genindex`
-* :ref:`modindex`
-* :ref:`search`
+.. ifconfig:: builder == 'html'
+
+  * :ref:`genindex`
+  * :ref:`modindex`
+  * :ref:`search`
+
+.. ifconfig:: builder != 'html'
+
+  * :ref:`genindex`
+  * :ref:`search`

docs/kubernetes.rst

@@ -32,6 +32,58 @@ Configuration
 
 Patroni Kubernetes :ref:`settings <kubernetes_settings>` and :ref:`environment variables <kubernetes_environment>` are described in the general chapters of the documentation.
 
+.. _kubernetes_role_values:
+
+Customize role label
+^^^^^^^^^^^^^^^^^^^^
+
+By default, Patroni will set corresponding labels on the pod it runs in based on node's role, such as ``role=master``.
+The key and value of label can be customized by `kubernetes.role_label`, `kubernetes.leader_label_value`, `kubernetes.follower_label_value` and `kubernetes.standby_leader_label_value`.
+
+Note that if you migrate from default role labels to custom ones, you can reduce downtime by following migration steps:
+
+1. Add a temporary label using original role value for the pod with `kubernetes.tmp_role_label` (like ``tmp_role``). Once pods are restarted they will get following labels set by Patroni:
+
+  .. code:: YAML
+
+    labels:
+      cluster-name: foo
+      role: master
+      tmp_role: master
+
+2. After all pods have been updated, modify the service selector to select the temporary label.
+
+  .. code:: YAML
+
+    selector:
+      cluster-name: foo
+      tmp_role: master
+
+3. Add your custom role label (e.g., set `kubernetes.leader_label_value=primary`). Once pods are restarted they will get following new labels set by Patroni:
+
+  .. code:: YAML
+
+    labels:
+      cluster-name: foo
+      role: primary
+      tmp_role: master
+
+4. After all pods have been updated again, modify the service selector to use new role value.
+
+  .. code:: YAML
+
+    selector:
+      cluster-name: foo
+      role: primary
+
+5. Finally, remove the temporary label from your configuration and update all pods.
+
+  .. code:: YAML
+
+    labels:
+      cluster-name: foo
+      role: primary
+
 Examples
 --------
 

docs/patroni_configuration.rst

@@ -0,0 +1,108 @@
+.. _patroni_configuration:
+
+Patroni configuration
+=====================
+
+.. toctree::
+   :hidden:
+
+   dynamic_configuration
+   yaml_configuration
+   ENVIRONMENT
+
+
+There are 3 types of Patroni configuration:
+
+- Global :ref:`dynamic configuration <dynamic_configuration>`.
+	These options are stored in the DCS (Distributed Configuration Store) and applied on all cluster nodes.
+	Dynamic configuration can be set at any time using ``patronictl edit-config`` tool or Patroni :ref:`REST API <rest_api>`.
+	If the options changed are not part of the startup configuration, they are applied asynchronously (upon the next wake up cycle)
+	to every node, which gets subsequently reloaded.
+	If the node requires a restart to apply the configuration (for `PostgreSQL parameters <https://www.postgresql.org/docs/current/view-pg-settings.html>`__ with context postmaster, if their values
+	have changed), a special flag ``pending_restart`` indicating this is set in the members.data JSON.
+	Additionally, the node status indicates this by showing ``"restart_pending": true``.
+
+- Local :ref:`configuration file <yaml_configuration>` (patroni.yml).
+	These options are defined in the configuration file and take precedence over dynamic configuration.
+	``patroni.yml`` can be changed and reloaded at runtime (without restart of Patroni) by sending SIGHUP to the Patroni process, performing ``POST /reload`` REST-API request or executing ``patronictl reload``. Local configuration can be either a single YAML file or a directory. When it is a directory, all YAML files in that directory are loaded one by one in sorted order. In case a key is defined in multiple files, the occurrence in the last file takes precedence.
+
+- :ref:`Environment configuration <environment>`.
+	It is possible to set/override some of the "Local" configuration parameters with environment variables.
+	Environment configuration is very useful when you are running in a dynamic environment and you don't know some of the parameters in advance (for example it's not possible to know your external IP address when you are running inside ``docker``).
+
+
+Important rules
+---------------
+
+PostgreSQL parameters controlled by Patroni
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+Some of the PostgreSQL parameters **must hold the same values on the primary and the replicas**. For those, **values set either in the local patroni configuration files or via the environment variables take no effect**. To alter or set their values one must change the shared configuration in the DCS. Below is the actual list of such parameters together with the default values:
+
+- **max_connections**: 100
+- **max_locks_per_transaction**: 64
+- **max_worker_processes**: 8
+- **max_prepared_transactions**: 0
+- **wal_level**: hot_standby
+- **wal_log_hints**: on
+- **track_commit_timestamp**: off
+
+For the parameters below, PostgreSQL does not require equal values among the primary and all the replicas. However, considering the possibility of a replica to become the primary at any time, it doesn't really make sense to set them differently; therefore, **Patroni restricts setting their values to the** :ref:`dynamic configuration <dynamic_configuration>`.
+
+- **max_wal_senders**: 5
+- **max_replication_slots**: 5
+- **wal_keep_segments**: 8
+- **wal_keep_size**: 128MB
+
+These parameters are validated to ensure they are sane, or meet a minimum value.
+
+There are some other Postgres parameters controlled by Patroni:
+
+- **listen_addresses** - is set either from ``postgresql.listen`` or from ``PATRONI_POSTGRESQL_LISTEN`` environment variable
+- **port** - is set either from ``postgresql.listen`` or from ``PATRONI_POSTGRESQL_LISTEN`` environment variable
+- **cluster_name** - is set either from ``scope`` or from ``PATRONI_SCOPE`` environment variable
+- **hot_standby: on**
+
+To be on the safe side parameters from the above lists are not written into ``postgresql.conf``, but passed as a list of arguments to the ``pg_ctl start`` which gives them the highest precedence, even above `ALTER SYSTEM <https://www.postgresql.org/docs/current/static/sql-altersystem.html>`__
+
+There also are some parameters like **postgresql.listen**, **postgresql.data_dir** that **can be set only locally**, i.e. in the Patroni :ref:`config file <yaml_configuration>` or via :ref:`configuration <environment>` variable. In most cases the local configuration will override the dynamic configuration.
+
+
+When applying the local or dynamic configuration options, the following actions are taken:
+
+- The node first checks if there is a `postgresql.base.conf` or if the ``custom_conf`` parameter is set.
+- If the ``custom_conf`` parameter is set, it will take the file specified on it as a base configuration, ignoring `postgresql.base.conf` and `postgresql.conf`.
+- If the ``custom_conf`` parameter is not set and `postgresql.base.conf` exists, it contains the renamed "original" configuration and it will be used as a base configuration.
+- If there is no ``custom_conf``` nor `postgresql.base.conf`, the original `postgresql.conf`` is taken and renamed to postgresql.base.conf.
+- The dynamic options (with the exceptions above) are dumped into the `postgresql.conf`` and an include is set in
+  postgresql.conf to the used base configuration (either `postgresql.base.conf` or what is on ``custom_conf``). Therefore, we would be able to apply new options without re-reading the configuration file to check if the include is present not.
+- Some parameters that are essential for Patroni to manage the cluster are overridden using the command line.
+- If some of the options that require restart are changed (we should look at the context in pg_settings and at the actual
+  values of those options), a pending_restart flag of a given node is set. This flag is reset on any restart.
+
+The parameters would be applied in the following order (run-time are given the highest priority):
+
+1. load parameters from file `postgresql.base.conf` (or from a ``custom_conf`` file, if set)
+2. load parameters from file `postgresql.conf`
+3. load parameters from file `postgresql.auto.conf`
+4. run-time parameter using `-o --name=value`
+
+This allows configuration for all the nodes (2), configuration for a specific node using ``ALTER SYSTEM`` (3) and ensures that parameters essential to the running of Patroni are enforced (4), as well as leaves room for configuration tools that manage `postgresql.conf` directly without involving Patroni (1).
+
+
+Patroni configuration parameters
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+Also the following Patroni configuration options **can be changed only dynamically**:
+
+- **ttl**: 30
+- **loop_wait**: 10
+- **retry_timeouts**: 10
+- **maximum_lag_on_failover**: 1048576
+- **max_timelines_history**: 0
+- **check_timeline**: false
+- **postgresql.use_slots**: true
+
+Upon changing these options, Patroni will read the relevant section of the configuration stored in DCS and change its run-time values.
+
+Patroni nodes are dumping the state of the DCS options to disk upon for every change of the configuration into the file ``patroni.dynamic.json`` located in the Postgres data directory. Only the leader is allowed to restore these options from the on-disk dump if these are completely absent from the DCS or if they are invalid.

docs/replication_modes.rst

@@ -49,7 +49,7 @@ on at least two nodes, enable ``synchronous_mode_strict`` in addition to the
 ``synchronous_mode``. This parameter prevents Patroni from switching off the
 synchronous replication on the primary when no synchronous standby candidates
 are available. As a downside, the primary is not be available for writes
-(unless the Postgres transaction explicitly turns of ``synchronous_mode``),
+(unless the Postgres transaction explicitly turns off ``synchronous_mode``),
 blocking all client write requests until at least one synchronous replica comes
 up.
 

docs/rest_api.rst

@@ -30,7 +30,8 @@ For all health check ``GET`` requests Patroni returns a JSON document with the s
 
 - ``GET /replica?tag_key1=value1&tag_key2=value2``: replica check endpoint. In addition, It will also check for user defined tags ``key1`` and ``key2`` and their respective values in the **tags** section of the yaml configuration management. If the tag isn't defined for an instance, or if the value in the yaml configuration doesn't match the querying value, it will return HTTP Status Code 503.
 
- In the following requests, since we are checking for the leader or standby-leader status, Patroni doesn't apply any of the user defined tags and they will be ignored.
+  In the following requests, since we are checking for the leader or standby-leader status, Patroni doesn't apply any of the user defined tags and they will be ignored.
+
   - ``GET /?tag_key1=value1&tag_key2=value2``
   - ``GET /leader?tag_key1=value1&tag_key2=value2``
   - ``GET /primary?tag_key1=value1&tag_key2=value2``
@@ -140,8 +141,8 @@ Retrieve the Patroni metrics in Prometheus format through the ``GET /metrics`` e
 	# TYPE patroni_replica gauge
 	patroni_replica{scope="batman"} 0
 	# HELP patroni_sync_standby Value is 1 if this node is a sync standby replica, 0 otherwise.
-        # TYPE patroni_sync_standby gauge
-        patroni_sync_standby{scope="batman"} 0
+	# TYPE patroni_sync_standby gauge
+	patroni_sync_standby{scope="batman"} 0
 	# HELP patroni_xlog_received_location Current location of the received Postgres transaction log, 0 if this node is not a replica.
 	# TYPE patroni_xlog_received_location counter
 	patroni_xlog_received_location{scope="batman"} 0
@@ -154,6 +155,12 @@ Retrieve the Patroni metrics in Prometheus format through the ``GET /metrics`` e
 	# HELP patroni_xlog_paused Value is 1 if the Postgres xlog is paused, 0 otherwise.
 	# TYPE patroni_xlog_paused gauge
 	patroni_xlog_paused{scope="batman"} 0
+	# HELP patroni_postgres_streaming Value is 1 if Postgres is streaming, 0 otherwise.
+	# TYPE patroni_postgres_streaming gauge
+	patroni_postgres_streaming{scope="batman"} 1
+	# HELP patroni_postgres_in_archive_recovery Value is 1 if Postgres is replicating from archive, 0 otherwise.
+	# TYPE patroni_postgres_in_archive_recovery gauge
+	patroni_postgres_in_archive_recovery{scope="batman"} 0
 	# HELP patroni_postgres_server_version Version of Postgres (if running), 0 otherwise.
 	# TYPE patroni_postgres_server_version gauge
 	patroni_postgres_server_version {scope="batman"} 140004

docs/security.rst

@@ -13,7 +13,7 @@ Patroni and patronictl both store and retrieve data to/from the DCS.
 
 Despite DCS doesn't contain any sensitive information, it allows changing some of Patroni/Postgres configuration. Therefore the very first thing that should be protected is DCS itself.
 
-The details of protection depend on the type of DCS used. The authentication and encryption parameters (tokens/basic-auth/client certificates) for the supported types of DCS are covered in :ref:`SETTINGS <bootstrap_settings>`
+The details of protection depend on the type of DCS used. The authentication and encryption parameters (tokens/basic-auth/client certificates) for the supported types of DCS are covered in :ref:`settings <yaml_configuration>`.
 
 The general recommendation is to enable TLS for all DCS communication.
 
@@ -32,6 +32,6 @@ When TLS for the REST API is enabled and a PKI is established, mutual authentica
 
 The ``restapi`` section parameters enable TLS client authentication to the server. Depending on the value of the ``verify_client`` parameter, the API server requires a successful client certificate verification for both safe and unsafe API calls (``verify_client: required``), or only for unsafe API calls (``verify_client: optional``), or for no API calls (``verify_client: none``).
 
-The ``ctl`` section parameters enable TLS server authentication to the client (the ``patronictl`` tool which uses the same config as patroni). Set ``insecure: true`` to disable the server certificate verification by the client. See :ref:`SETTINGS <patronictl_settings>` for a detailed description of the TLS client parameters.
+The ``ctl`` section parameters enable TLS server authentication to the client (the ``patronictl`` tool which uses the same config as patroni). Set ``insecure: true`` to disable the server certificate verification by the client. See :ref:`settings <patronictl_settings>` for a detailed description of the TLS client parameters.
 
 Protecting the PostgreSQL database proper from unauthorized access is beyond the scope of this document and is covered in https://www.postgresql.org/docs/current/client-authentication.html

docs/yaml_configuration.rst

@@ -0,0 +1,394 @@
+.. _yaml_configuration:
+
+============================
+YAML Configuration Settings
+============================
+
+
+Global/Universal
+----------------
+-  **name**: the name of the host. Must be unique for the cluster.
+-  **namespace**: path within the configuration store where Patroni will keep information about the cluster. Default value: "/service"
+-  **scope**: cluster name
+
+Log
+---
+-  **level**: sets the general logging level. Default value is **INFO** (see `the docs for Python logging <https://docs.python.org/3.6/library/logging.html#levels>`_)
+-  **traceback\_level**: sets the level where tracebacks will be visible. Default value is **ERROR**. Set it to **DEBUG** if you want to see tracebacks only if you enable **log.level=DEBUG**.
+-  **format**: sets the log formatting string. Default value is **%(asctime)s %(levelname)s: %(message)s** (see `the LogRecord attributes <https://docs.python.org/3.6/library/logging.html#logrecord-attributes>`_)
+-  **dateformat**: sets the datetime formatting string. (see the `formatTime() documentation <https://docs.python.org/3.6/library/logging.html#logging.Formatter.formatTime>`_)
+-  **max\_queue\_size**: Patroni is using two-step logging. Log records are written into the in-memory queue and there is a separate thread which pulls them from the queue and writes to stderr or file. The maximum size of the internal queue is limited by default by **1000** records, which is enough to keep logs for the past 1h20m.
+-  **dir**: Directory to write application logs to. The directory must exist and be writable by the user executing Patroni. If you set this value, the application will retain 4 25MB logs by default. You can tune those retention values with `file_num` and `file_size` (see below).
+-  **file\_num**: The number of application logs to retain.
+-  **file\_size**: Size of patroni.log file (in bytes) that triggers a log rolling.
+-  **loggers**: This section allows redefining logging level per python module
+
+   -  **patroni.postmaster: WARNING**
+   -  **urllib3: DEBUG**
+
+.. _bootstrap_settings:
+
+Bootstrap configuration
+-----------------------
+-  **bootstrap**:
+
+   -  **dcs**: This section will be written into `/<namespace>/<scope>/config` of the given configuration store after initializing of new cluster. The global dynamic configuration for the cluster. Under the ``bootstrap.dcs`` you can put any of the parameters described in the :ref:`Dynamic Configuration settings <dynamic_configuration>` and after Patroni initialized (bootstrapped) the new cluster, it will write this section into `/<namespace>/<scope>/config` of the configuration store. All later changes of ``bootstrap.dcs`` will not take any effect! If you want to change them please use either ``patronictl edit-config`` or Patroni :ref:`REST API <rest_api>`.
+   -  **method**: custom script to use for bootstrapping this cluster.
+
+      See :ref:`custom bootstrap methods documentation <custom_bootstrap>` for details.
+      When ``initdb`` is specified revert to the default ``initdb`` command. ``initdb`` is also triggered when no ``method``
+      parameter is present in the configuration file.
+   -  **initdb**: (optional) list options to be passed on to initdb.
+
+      -  **- data-checksums**: Must be enabled when pg_rewind is needed on 9.3.
+      -  **- encoding: UTF8**: default encoding for new databases.
+      -  **- locale: UTF8**: default locale for new databases.
+   -  **users**: Some additional users which need to be created after initializing new cluster, see :ref:`Bootstrap users configuration <bootstrap_users_configuration>` below.
+   -  **post\_bootstrap** or **post\_init**: An additional script that will be executed after initializing the cluster. The script receives a connection string URL (with the cluster superuser as a user name). The PGPASSFILE variable is set to the location of pgpass file.
+
+.. _bootstrap_users_configuration:
+
+Bootstrap users configuration
+=============================
+
+Users which need to be created after initializing the cluster:
+
+-  **admin**: the name of user
+
+  -  **password**: (optional) password for the user
+  -  **options**: list of options for CREATE USER statement
+
+    -  **- createrole**
+    -  **- createdb**
+
+.. _citus_settings:
+
+Citus
+-----
+Enables integration Patroni with `Citus <https://docs.citusdata.com>`__. If configured, Patroni will take care of registering Citus worker nodes on the coordinator. You can find more information about Citus support :ref:`here <citus>`.
+
+-  **group**: the Citus group id, integer. Use ``0`` for coordinator and ``1``, ``2``, etc... for workers
+-  **database**: the database where ``citus`` extension should be created. Must be the same on the coordinator and all workers. Currently only one database is supported.
+
+.. _consul_settings:
+
+Consul
+------
+Most of the parameters are optional, but you have to specify one of the **host** or **url**
+
+-  **host**: the host:port for the Consul local agent.
+-  **url**: url for the Consul local agent, in format: http(s)://host:port.
+-  **port**: (optional) Consul port.
+-  **scheme**: (optional) **http** or **https**, defaults to **http**.
+-  **token**: (optional) ACL token.
+-  **verify**: (optional) whether to verify the SSL certificate for HTTPS requests.
+-  **cacert**: (optional) The ca certificate. If present it will enable validation.
+-  **cert**: (optional) file with the client certificate.
+-  **key**: (optional) file with the client key. Can be empty if the key is part of **cert**.
+-  **dc**: (optional) Datacenter to communicate with. By default the datacenter of the host is used.
+-  **consistency**: (optional) Select consul consistency mode. Possible values are ``default``, ``consistent``, or ``stale`` (more details in `consul API reference <https://www.consul.io/api/features/consistency.html/>`__)
+-  **checks**: (optional) list of Consul health checks used for the session. By default an empty list is used.
+-  **register\_service**: (optional) whether or not to register a service with the name defined by the scope parameter and the tag master, primary, replica, or standby-leader depending on the node's role. Defaults to **false**.
+-  **service\_tags**: (optional) additional static tags to add to the Consul service apart from the role (``master``/``primary``/``replica``/``standby-leader``). By default an empty list is used.
+-  **service\_check\_interval**: (optional) how often to perform health check against registered url. Defaults to '5s'.
+-  **service\_check\_tls\_server\_name**: (optional) overide SNI host when connecting via TLS, see also `consul agent check API reference <https://www.consul.io/api-docs/agent/check#tlsservername>`__.
+
+The ``token`` needs to have the following ACL permissions:
+
+::
+
+    service_prefix "${scope}" {
+        policy = "write"
+    }
+    key_prefix "${namespace}/${scope}" {
+        policy = "write"
+    }
+    session_prefix "" {
+        policy = "write"
+    }
+
+Etcd
+----
+Most of the parameters are optional, but you have to specify one of the **host**, **hosts**, **url**, **proxy** or **srv**
+
+-  **host**: the host:port for the etcd endpoint.
+-  **hosts**: list of etcd endpoint in format host1:port1,host2:port2,etc... Could be a comma separated string or an actual yaml list.
+-  **use\_proxies**: If this parameter is set to true, Patroni will consider **hosts** as a list of proxies and will not perform a topology discovery of etcd cluster.
+-  **url**: url for the etcd.
+-  **proxy**: proxy url for the etcd. If you are connecting to the etcd using proxy, use this parameter instead of **url**.
+-  **srv**: Domain to search the SRV record(s) for cluster autodiscovery. Patroni will try to query these SRV service names for specified domain (in that order until first success): ``_etcd-client-ssl``, ``_etcd-client``, ``_etcd-ssl``, ``_etcd``, ``_etcd-server-ssl``, ``_etcd-server``. If SRV records for ``_etcd-server-ssl`` or ``_etcd-server`` are retrieved then ETCD peer protocol is used do query ETCD for available members. Otherwise hosts from SRV records will be used.
+-  **srv\_suffix**: Configures a suffix to the SRV name that is queried during discovery. Use this flag to differentiate between multiple etcd clusters under the same domain. Works only with conjunction with **srv**. For example, if ``srv_suffix: foo`` and ``srv: example.org`` are set, the following DNS SRV query is made:``_etcd-client-ssl-foo._tcp.example.com`` (and so on for every possible ETCD SRV service name).
+-  **protocol**: (optional) http or https, if not specified http is used. If the **url** or **proxy** is specified - will take protocol from them.
+-  **username**: (optional) username for etcd authentication.
+-  **password**: (optional) password for etcd authentication.
+-  **cacert**: (optional) The ca certificate. If present it will enable validation.
+-  **cert**: (optional) file with the client certificate.
+-  **key**: (optional) file with the client key. Can be empty if the key is part of **cert**.
+
+Etcdv3
+------
+If you want that Patroni works with Etcd cluster via protocol version 3, you need to use the ``etcd3`` section in the Patroni configuration file. All configuration parameters are the same as for ``etcd``.
+
+.. warning::
+    Keys created with protocol version 2 are not visible with protocol version 3 and the other way around, therefore it is not possible to switch from ``etcd`` to ``etcd3`` just by updating Patroni config file.
+
+
+ZooKeeper
+----------
+-  **hosts**: List of ZooKeeper cluster members in format: ['host1:port1', 'host2:port2', 'etc...'].
+-  **use_ssl**: (optional) Whether SSL is used or not. Defaults to ``false``. If set to ``false``, all SSL specific parameters are ignored.
+-  **cacert**: (optional) The CA certificate. If present it will enable validation.
+-  **cert**: (optional) File with the client certificate.
+-  **key**: (optional) File with the client key.
+-  **key_password**: (optional) The client key password.
+-  **verify**: (optional) Whether to verify certificate or not. Defaults to ``true``.
+-  **set_acls**: (optional) If set, configure Kazoo to apply a default ACL to each ZNode that it creates. ACLs will assume 'x509' schema and should be specified as a dictionary with the principal as the key and one or more permissions as a list in the value.  Permissions may be one of ``CREATE``, ``READ``, ``WRITE``, ``DELETE`` or ``ADMIN``.  For example, ``set_acls: {CN=principal1: [CREATE, READ], CN=principal2: [ALL]}``.
+
+.. note::
+    It is required to install ``kazoo>=2.6.0`` to support SSL.
+
+
+Exhibitor
+---------
+-  **hosts**: initial list of Exhibitor (ZooKeeper) nodes in format: 'host1,host2,etc...'. This list updates automatically whenever the Exhibitor (ZooKeeper) cluster topology changes.
+-  **poll\_interval**: how often the list of ZooKeeper and Exhibitor nodes should be updated from Exhibitor.
+-  **port**: Exhibitor port.
+
+.. _kubernetes_settings:
+
+Kubernetes
+----------
+-  **bypass\_api\_service**: (optional) When communicating with the Kubernetes API, Patroni is usually relying on the `kubernetes` service, the address of which is exposed in the pods via the `KUBERNETES_SERVICE_HOST` environment variable. If `bypass_api_service` is set to ``true``, Patroni will resolve the list of API nodes behind the service and connect directly to them.
+-  **namespace**: (optional) Kubernetes namespace where Patroni pod is running. Default value is `default`.
+-  **labels**: Labels in format ``{label1: value1, label2: value2}``. These labels will be used to find existing objects (Pods and either Endpoints or ConfigMaps) associated with the current cluster. Also Patroni will set them on every object (Endpoint or ConfigMap) it creates.
+-  **scope\_label**: (optional) name of the label containing cluster name. Default value is `cluster-name`.
+-  **role\_label**: (optional) name of the label containing role (master or replica or other custom value). Patroni will set this label on the pod it runs in. Default value is ``role``.
+-  **leader\_label\_value**: (optional) value of the pod label when Postgres role is ``master``. Default value is ``master``.
+-  **follower\_label\_value**: (optional) value of the pod label when Postgres role is ``replica``. Default value is ``replica``.
+-  **standby\_leader\_label\_value**: (optional) value of the pod label when Postgres role is ``standby_leader``. Default value is ``master``.
+-  **tmp_\role\_label**: (optional) name of the temporary label containing role (master or replica). Value of this label will always use the default of corresponding role. Set only when necessary.
+-  **use\_endpoints**: (optional) if set to true, Patroni will use Endpoints instead of ConfigMaps to run leader elections and keep cluster state.
+-  **pod\_ip**: (optional) IP address of the pod Patroni is running in. This value is required when `use_endpoints` is enabled and is used to populate the leader endpoint subsets when the pod's PostgreSQL is promoted.
+-  **ports**: (optional) if the Service object has the name for the port, the same name must appear in the Endpoint object, otherwise service won't work. For example, if your service is defined as ``{Kind: Service, spec: {ports: [{name: postgresql, port: 5432, targetPort: 5432}]}}``, then you have to set ``kubernetes.ports: [{"name": "postgresql", "port": 5432}]`` and Patroni will use it for updating subsets of the leader Endpoint. This parameter is used only if `kubernetes.use_endpoints` is set.
+-  **cacert**: (optional) Specifies the file with the CA_BUNDLE file with certificates of trusted CAs to use while verifying Kubernetes API SSL certs. If not provided, patroni will use the value provided by the ServiceAccount secret.
+-  **retriable\_http\_codes**: (optional) list of HTTP status codes from K8s API to retry on. By default Patroni is retrying on ``500``, ``503``, and ``504``, or if K8s API response has ``retry-after`` HTTP header.
+
+
+.. _raft_settings:
+
+Raft (deprecated)
+-----------------
+-  **self\_addr**: ``ip:port`` to listen on for Raft connections. The ``self_addr`` must be accessible from other nodes of the cluster. If not set, the node will not participate in consensus.
+-  **bind\_addr**: (optional) ``ip:port`` to listen on for Raft connections. If not specified the ``self_addr`` will be used.
+-  **partner\_addrs**: list of other Patroni nodes in the cluster in format: ['ip1:port', 'ip2:port', 'etc...']
+-  **data\_dir**: directory where to store Raft log and snapshot. If not specified the current working directory is used.
+-  **password**: (optional) Encrypt Raft traffic with a specified password, requires ``cryptography`` python module.
+
+   Short FAQ about Raft implementation
+
+   - Q: How to list all the nodes providing consensus?
+
+     A: ``syncobj_admin -conn host:port -status`` where the host:port is the address of one of the cluster nodes
+
+   - Q: Node that was a part of consensus and has gone and I can't reuse the same IP for other node. How to remove this node from the consensus?
+
+     A: ``syncobj_admin -conn host:port -remove host2:port2`` where the ``host2:port2`` is the address of the node you want to remove from consensus.
+
+   - Q: Where to get the ``syncobj_admin`` utility?
+
+     A: It is installed together with ``pysyncobj`` module (python RAFT implementation), which is Patroni dependency.
+
+   - Q: it is possible to run Patroni node without adding in to the consensus?
+
+     A: Yes, just comment out or remove ``raft.self_addr`` from Patroni configuration.
+
+   - Q: It is possible to run Patroni and PostgreSQL only on two nodes?
+
+     A: Yes, on the third node you can run ``patroni_raft_controller`` (without Patroni and PostgreSQL). In such a setup, one can temporarily lose one node without affecting the primary.
+
+
+.. _postgresql_settings:
+
+PostgreSQL
+----------
+-  **postgresql**:
+
+   -  **authentication**:
+
+      -  **superuser**:
+
+         -  **username**: name for the superuser, set during initialization (initdb) and later used by Patroni to connect to the postgres.
+         -  **password**: password for the superuser, set during initialization (initdb).
+         -  **sslmode**: (optional) maps to the `sslmode <https://www.postgresql.org/docs/current/libpq-connect.html#LIBPQ-CONNECT-SSLMODE>`__ connection parameter, which allows a client to specify the type of TLS negotiation mode with the server. For more information on how each mode works, please visit the `PostgreSQL documentation <https://www.postgresql.org/docs/current/libpq-ssl.html#LIBPQ-SSL-SSLMODE-STATEMENTS>`__. The default mode is ``prefer``.
+         -  **sslkey**: (optional) maps to the `sslkey <https://www.postgresql.org/docs/current/libpq-connect.html#LIBPQ-CONNECT-SSLKEY>`__ connection parameter, which specifies the location of the secret key used with the client's certificate.
+         -  **sslpassword**: (optional) maps to the `sslpassword <https://www.postgresql.org/docs/current/libpq-connect.html#LIBPQ-CONNECT-SSLPASSWORD>`__ connection parameter, which specifies the password for the secret key specified in ``sslkey``.
+         -  **sslcert**: (optional) maps to the `sslcert <https://www.postgresql.org/docs/current/libpq-connect.html#LIBPQ-CONNECT-SSLCERT>`__ connection parameter, which specifies the location of the client certificate.
+         -  **sslrootcert**: (optional) maps to the `sslrootcert <https://www.postgresql.org/docs/current/libpq-connect.html#LIBPQ-CONNECT-SSLROOTCERT>`__ connection parameter, which specifies the location of a file containing one ore more certificate authorities (CA) certificates that the client will use to verify a server's certificate.
+         -  **sslcrl**: (optional) maps to the `sslcrl <https://www.postgresql.org/docs/current/libpq-connect.html#LIBPQ-CONNECT-SSLCRL>`__ connection parameter, which specifies the location of a file containing a certificate revocation list. A client will reject connecting to any server that has a certificate present in this list.
+         -  **sslcrldir**: (optional) maps to the `sslcrldir <https://www.postgresql.org/docs/current/libpq-connect.html#LIBPQ-CONNECT-SSLCRLDIR>`__ connection parameter, which specifies the location of a directory with files containing a certificate revocation list. A client will reject connecting to any server that has a certificate present in this list.
+         -  **gssencmode**: (optional) maps to the `gssencmode <https://www.postgresql.org/docs/current/libpq-connect.html#LIBPQ-CONNECT-GSSENCMODE>`__ connection parameter, which determines whether or with what priority a secure GSS TCP/IP connection will be negotiated with the server
+         -  **channel_binding**: (optional) maps to the `channel_binding <https://www.postgresql.org/docs/current/libpq-connect.html#LIBPQ-CONNECT-CHANNEL-BINDING>`__ connection parameter, which controls the client's use of channel binding.
+      -  **replication**:
+
+         -  **username**: replication username; the user will be created during initialization. Replicas will use this user to access the replication source via streaming replication
+         -  **password**: replication password; the user will be created during initialization.
+         -  **sslmode**: (optional) maps to the `sslmode <https://www.postgresql.org/docs/current/libpq-connect.html#LIBPQ-CONNECT-SSLMODE>`__ connection parameter, which allows a client to specify the type of TLS negotiation mode with the server. For more information on how each mode works, please visit the `PostgreSQL documentation <https://www.postgresql.org/docs/current/libpq-ssl.html#LIBPQ-SSL-SSLMODE-STATEMENTS>`__. The default mode is ``prefer``.
+         -  **sslkey**: (optional) maps to the `sslkey <https://www.postgresql.org/docs/current/libpq-connect.html#LIBPQ-CONNECT-SSLKEY>`__ connection parameter, which specifies the location of the secret key used with the client's certificate.
+         -  **sslpassword**: (optional) maps to the `sslpassword <https://www.postgresql.org/docs/current/libpq-connect.html#LIBPQ-CONNECT-SSLPASSWORD>`__ connection parameter, which specifies the password for the secret key specified in ``sslkey``.
+         -  **sslcert**: (optional) maps to the `sslcert <https://www.postgresql.org/docs/current/libpq-connect.html#LIBPQ-CONNECT-SSLCERT>`__ connection parameter, which specifies the location of the client certificate.
+         -  **sslrootcert**: (optional) maps to the `sslrootcert <https://www.postgresql.org/docs/current/libpq-connect.html#LIBPQ-CONNECT-SSLROOTCERT>`__ connection parameter, which specifies the location of a file containing one ore more certificate authorities (CA) certificates that the client will use to verify a server's certificate.
+         -  **sslcrl**: (optional) maps to the `sslcrl <https://www.postgresql.org/docs/current/libpq-connect.html#LIBPQ-CONNECT-SSLCRL>`__ connection parameter, which specifies the location of a file containing a certificate revocation list. A client will reject connecting to any server that has a certificate present in this list.
+         -  **sslcrldir**: (optional) maps to the `sslcrldir <https://www.postgresql.org/docs/current/libpq-connect.html#LIBPQ-CONNECT-SSLCRLDIR>`__ connection parameter, which specifies the location of a directory with files containing a certificate revocation list. A client will reject connecting to any server that has a certificate present in this list.
+         -  **gssencmode**: (optional) maps to the `gssencmode <https://www.postgresql.org/docs/current/libpq-connect.html#LIBPQ-CONNECT-GSSENCMODE>`__ connection parameter, which determines whether or with what priority a secure GSS TCP/IP connection will be negotiated with the server
+         -  **channel_binding**: (optional) maps to the `channel_binding <https://www.postgresql.org/docs/current/libpq-connect.html#LIBPQ-CONNECT-CHANNEL-BINDING>`__ connection parameter, which controls the client's use of channel binding.
+      -  **rewind**:
+
+         -  **username**: (optional) name for the user for ``pg_rewind``; the user will be created during initialization of postgres 11+ and all necessary `permissions <https://www.postgresql.org/docs/11/app-pgrewind.html#id-1.9.5.8.8>`__ will be granted.
+         -  **password**: (optional) password for the user for ``pg_rewind``; the user will be created during initialization.
+         -  **sslmode**: (optional) maps to the `sslmode <https://www.postgresql.org/docs/current/libpq-connect.html#LIBPQ-CONNECT-SSLMODE>`__ connection parameter, which allows a client to specify the type of TLS negotiation mode with the server. For more information on how each mode works, please visit the `PostgreSQL documentation <https://www.postgresql.org/docs/current/libpq-ssl.html#LIBPQ-SSL-SSLMODE-STATEMENTS>`__. The default mode is ``prefer``.
+         -  **sslkey**: (optional) maps to the `sslkey <https://www.postgresql.org/docs/current/libpq-connect.html#LIBPQ-CONNECT-SSLKEY>`__ connection parameter, which specifies the location of the secret key used with the client's certificate.
+         -  **sslpassword**: (optional) maps to the `sslpassword <https://www.postgresql.org/docs/current/libpq-connect.html#LIBPQ-CONNECT-SSLPASSWORD>`__ connection parameter, which specifies the password for the secret key specified in ``sslkey``.
+         -  **sslcert**: (optional) maps to the `sslcert <https://www.postgresql.org/docs/current/libpq-connect.html#LIBPQ-CONNECT-SSLCERT>`__ connection parameter, which specifies the location of the client certificate.
+         -  **sslrootcert**: (optional) maps to the `sslrootcert <https://www.postgresql.org/docs/current/libpq-connect.html#LIBPQ-CONNECT-SSLROOTCERT>`__ connection parameter, which specifies the location of a file containing one ore more certificate authorities (CA) certificates that the client will use to verify a server's certificate.
+         -  **sslcrl**: (optional) maps to the `sslcrl <https://www.postgresql.org/docs/current/libpq-connect.html#LIBPQ-CONNECT-SSLCRL>`__ connection parameter, which specifies the location of a file containing a certificate revocation list. A client will reject connecting to any server that has a certificate present in this list.
+         -  **sslcrldir**: (optional) maps to the `sslcrldir <https://www.postgresql.org/docs/current/libpq-connect.html#LIBPQ-CONNECT-SSLCRLDIR>`__ connection parameter, which specifies the location of a directory with files containing a certificate revocation list. A client will reject connecting to any server that has a certificate present in this list.
+         -  **gssencmode**: (optional) maps to the `gssencmode <https://www.postgresql.org/docs/current/libpq-connect.html#LIBPQ-CONNECT-GSSENCMODE>`__ connection parameter, which determines whether or with what priority a secure GSS TCP/IP connection will be negotiated with the server
+         -  **channel_binding**: (optional) maps to the `channel_binding <https://www.postgresql.org/docs/current/libpq-connect.html#LIBPQ-CONNECT-CHANNEL-BINDING>`__ connection parameter, which controls the client's use of channel binding.
+
+   -  **callbacks**: callback scripts to run on certain actions. Patroni will pass the action, role and cluster name. (See scripts/aws.py as an example of how to write them.)
+
+      -  **on\_reload**: run this script when configuration reload is triggered.
+      -  **on\_restart**: run this script when the postgres restarts (without changing role).
+      -  **on\_role\_change**: run this script when the postgres is being promoted or demoted.
+      -  **on\_start**: run this script when the postgres starts.
+      -  **on\_stop**: run this script when the postgres stops.
+   -  **connect\_address**: IP address + port through which Postgres is accessible from other nodes and applications.
+   -  **proxy\_address**: IP address + port through which a connection pool (e.g. pgbouncer) running next to Postgres is accessible. The value is written to the member key in DCS as ``proxy_url`` and could be used/useful for service discovery.
+   -  **create\_replica\_methods**: an ordered list of the create methods for turning a Patroni node into a new replica.
+      "basebackup" is the default method; other methods are assumed to refer to scripts, each of which is configured as its
+      own config item. See :ref:`custom replica creation methods documentation <custom_replica_creation>` for further explanation.
+   -  **data\_dir**: The location of the Postgres data directory, either :ref:`existing <existing_data>` or to be initialized by Patroni.
+   -  **config\_dir**: The location of the Postgres configuration directory, defaults to the data directory. Must be writable by Patroni.
+   -  **bin\_dir**: (optional) Path to PostgreSQL binaries (pg_ctl, initdb, pg_controldata, pg_basebackup, postgres, pg_isready, pg_rewind). If not provided or is an empty string, PATH environment variable will be used to find the executables.
+   -  **bin\_name**: (optional) Make it possible to override Postgres binary names, if you are using a custom Postgres distribution:
+
+      - **pg\_ctl**: (optional) Custom name for ``pg_ctl`` binary.
+      - **initdb**: (optional) Custom name for ``initdb`` binary.
+      - **pg\controldata**: (optional) Custom name for ``pg_controldata`` binary.
+      - **pg\_basebackup**: (optional) Custom name for ``pg_basebackup`` binary.
+      - **postgres**: (optional) Custom name for ``postgres`` binary.
+      - **pg\_isready**: (optional) Custom name for ``pg_isready`` binary.
+      - **pg\_rewind**: (optional) Custom name for ``pg_rewind`` binary.
+   -  **listen**: IP address + port that Postgres listens to; must be accessible from other nodes in the cluster, if you're using streaming replication. Multiple comma-separated addresses are permitted, as long as the port component is appended after to the last one with a colon, i.e. ``listen: 127.0.0.1,127.0.0.2:5432``. Patroni will use the first address from this list to establish local connections to the PostgreSQL node.
+   -  **use\_unix\_socket**: specifies that Patroni should prefer to use unix sockets to connect to the cluster. Default value is ``false``. If ``unix_socket_directories`` is defined, Patroni will use the first suitable value from it to connect to the cluster and fallback to tcp if nothing is suitable. If ``unix_socket_directories`` is not specified in ``postgresql.parameters``, Patroni will assume that the default value should be used and omit ``host`` from the connection parameters.
+   -  **use\_unix\_socket\_repl**: specifies that Patroni should prefer to use unix sockets for replication user cluster connection. Default value is ``false``. If ``unix_socket_directories`` is defined, Patroni will use the first suitable value from it to connect to the cluster and fallback to tcp if nothing is suitable. If ``unix_socket_directories`` is not specified in ``postgresql.parameters``, Patroni will assume that the default value should be used and omit ``host`` from the connection parameters.
+   -  **pgpass**: path to the `.pgpass <https://www.postgresql.org/docs/current/static/libpq-pgpass.html>`__ password file. Patroni creates this file before executing pg\_basebackup, the post_init script and under some other circumstances. The location must be writable by Patroni.
+   -  **recovery\_conf**: additional configuration settings written to recovery.conf when configuring follower.
+   -  **custom\_conf** : path to an optional custom ``postgresql.conf`` file, that will be used in place of ``postgresql.base.conf``. The file must exist on all cluster nodes, be readable by PostgreSQL and will be included from its location on the real ``postgresql.conf``. Note that Patroni will not monitor this file for changes, nor backup it. However, its settings can still be overridden by Patroni's own configuration facilities - see :ref:`dynamic configuration <patroni_configuration>` for details.
+   -  **parameters**: list of configuration settings for Postgres. Many of these are required for replication to work.
+   -  **pg\_hba**: list of lines that Patroni will use to generate ``pg_hba.conf``. Patroni ignores this parameter if ``hba_file`` PostgreSQL parameter is set to a non-default value. Together with :ref:`dynamic configuration <dynamic_configuration>` this parameter simplifies management of ``pg_hba.conf``.
+
+      -  **- host all all 0.0.0.0/0 md5**
+      -  **- host replication replicator 127.0.0.1/32 md5**: A line like this is required for replication.
+   -  **pg\_ident**: list of lines that Patroni will use to generate ``pg_ident.conf``. Patroni ignores this parameter if ``ident_file`` PostgreSQL parameter is set to a non-default value. Together with :ref:`dynamic configuration <dynamic_configuration>` this parameter simplifies management of ``pg_ident.conf``.
+
+      -  **- mapname1 systemname1 pguser1**
+      -  **- mapname1 systemname2 pguser2**
+   -  **pg\_ctl\_timeout**: How long should pg_ctl wait when doing ``start``, ``stop`` or ``restart``. Default value is 60 seconds.
+   -  **use\_pg\_rewind**: try to use pg\_rewind on the former leader when it joins cluster as a replica.
+   -  **remove\_data\_directory\_on\_rewind\_failure**: If this option is enabled, Patroni will remove the PostgreSQL data directory and recreate the replica. Otherwise it will try to follow the new leader. Default value is **false**.
+   -  **remove\_data\_directory\_on\_diverged\_timelines**: Patroni will remove the PostgreSQL data directory and recreate the replica if it notices that timelines are diverging and the former primary can not start streaming from the new primary. This option is useful when ``pg_rewind`` can not be used. While performing timelines divergence check on PostgreSQL v10 and older Patroni will try to connect with replication credential to the "postgres" database. Hence, such access should be allowed in the pg_hba.conf. Default value is **false**.
+   -  **replica\_method**: for each create_replica_methods other than basebackup, you would add a configuration section of the same name. At a minimum, this should include "command" with a full path to the actual script to be executed. Other configuration parameters will be passed along to the script in the form "parameter=value".
+   -  **pre\_promote**: a fencing script that executes during a failover after acquiring the leader lock but before promoting the replica. If the script exits with a non-zero code, Patroni does not promote the replica and removes the leader key from DCS.
+   -  **before\_stop**: a script that executes immediately prior to stopping postgres. As opposed to a callback, this script runs synchronously, blocking shutdown until it has completed. The return code of this script does not impact whether shutdown proceeds afterwards.
+
+.. _restapi_settings:
+
+REST API
+--------
+-  **restapi**:
+
+   -  **connect\_address**: IP address (or hostname) and port, to access the Patroni's :ref:`REST API <rest_api>`. All the members of the cluster must be able to connect to this address, so unless the Patroni setup is intended for a demo inside the localhost, this address must be a non "localhost" or loopback address (ie: "localhost" or "127.0.0.1"). It can serve as an endpoint for HTTP health checks (read below about the "listen" REST API parameter), and also for user queries (either directly or via the REST API), as well as for the health checks done by the cluster members during leader elections (for example, to determine whether the leader is still running, or if there is a node which has a WAL position that is ahead of the one doing the query; etc.) The connect_address is put in the member key in DCS, making it possible to translate the member name into the address to connect to its REST API.
+   -  **listen**: IP address (or hostname) and port that Patroni will listen to for the REST API - to provide also the same health checks and cluster messaging between the participating nodes, as described above. to provide health-check information for HAProxy (or any other load balancer capable of doing a HTTP "OPTION" or "GET" checks).
+   -  **authentication**: (optional)
+
+      -  **username**: Basic-auth username to protect unsafe REST API endpoints.
+      -  **password**: Basic-auth password to protect unsafe REST API endpoints.
+   -  **certfile**: (optional): Specifies the file with the certificate in the PEM format. If the certfile is not specified or is left empty, the API server will work without SSL.
+   -  **keyfile**: (optional): Specifies the file with the secret key in the PEM format.
+   -  **keyfile\_password**: (optional): Specifies a password for decrypting the keyfile.
+   -  **cafile**: (optional): Specifies the file with the CA_BUNDLE with certificates of trusted CAs to use while verifying client certs.
+   -  **ciphers**: (optional): Specifies the permitted cipher suites (e.g. "ECDHE-RSA-AES256-GCM-SHA384:DHE-RSA-AES256-GCM-SHA384:ECDHE-RSA-AES128-GCM-SHA256:DHE-RSA-AES128-GCM-SHA256:!SSLv1:!SSLv2:!SSLv3:!TLSv1:!TLSv1.1")
+   -  **verify\_client**: (optional): ``none`` (default), ``optional`` or ``required``. When ``none`` REST API will not check client certificates. When ``required`` client certificates are required for all REST API calls. When ``optional`` client certificates are required for all unsafe REST API endpoints. When ``required`` is used, then client authentication succeeds, if the certificate signature verification succeeds.  For ``optional`` the client cert will only be checked for ``PUT``, ``POST``, ``PATCH``, and ``DELETE`` requests.
+   -  **allowlist**: (optional): Specifies the set of hosts that are allowed to call unsafe REST API endpoints. The single element could be a host name, an IP address or a network address using CIDR notation. By default ``allow all`` is used. In case if ``allowlist`` or ``allowlist_include_members`` are set, anything that is not included is rejected.
+   -  **allowlist\_include\_members**: (optional): If set to ``true`` it allows accessing unsafe REST API endpoints from other cluster members registered in DCS (IP address or hostname is taken from the members ``api_url``). Be careful, it might happen that OS will use a different IP for outgoing connections.
+   -  **http\_extra\_headers**: (optional): HTTP headers let the REST API server pass additional information with an HTTP response.
+   -  **https\_extra\_headers**: (optional): HTTPS headers let the REST API server pass additional information with an HTTP response when TLS is enabled. This will also pass additional information set in ``http_extra_headers``.
+   -  **request_queue_size**: (optional): Sets request queue size for TCP socket used by Patroni REST API.  Once the queue is full, further requests get a "Connection denied" error. The default value is 5.
+
+Here is an example of both **http_extra_headers** and **https_extra_headers**:
+
+.. code:: YAML
+
+        restapi:
+          listen: <listen>
+          connect_address: <connect_address>
+          authentication:
+            username: <username>
+            password: <password>
+          http_extra_headers:
+            'X-Frame-Options': 'SAMEORIGIN'
+            'X-XSS-Protection': '1; mode=block'
+            'X-Content-Type-Options': 'nosniff'
+          cafile: <ca file>
+          certfile: <cert>
+          keyfile: <key>
+          https_extra_headers:
+            'Strict-Transport-Security': 'max-age=31536000; includeSubDomains'
+
+.. warning::
+
+    - The ``restapi.connect_address`` must be accessible from all nodes of a given Patroni cluster. Internally Patroni is using it during the leader race to find nodes with minimal replication lag.
+    - If you enabled client certificates validation (``restapi.verify_client`` is set to ``required``), you also **must** provide **valid client certificates** in the ``ctl.certfile``, ``ctl.keyfile``, ``ctl.keyfile_password``. If not provided, Patroni will not work correctly.
+
+
+.. _patronictl_settings:
+
+CTL
+---
+-  **ctl**: (optional)
+
+   -  **authentication**:
+
+      -  **username**: Basic-auth username for accessing protected REST API endpoints. If not provided patronictl will use the value provided for REST API "username" parameter.
+      -  **password**: Basic-auth password for accessing protected REST API endpoints. If not provided patronictl will use the value provided for REST API "password" parameter.
+   -  **insecure**: Allow connections to REST API without verifying SSL certs.
+   -  **cacert**: Specifies the file with the CA_BUNDLE file or directory with certificates of trusted CAs to use while verifying REST API SSL certs. If not provided patronictl will use the value provided for REST API "cafile" parameter.
+   -  **certfile**: Specifies the file with the client certificate in the PEM format.
+   -  **keyfile**: Specifies the file with the client secret key in the PEM format.
+   -  **keyfile\_password**: Specifies a password for decrypting the client keyfile.
+
+Watchdog
+--------
+-  **mode**: ``off``, ``automatic`` or ``required``. When ``off`` watchdog is disabled. When ``automatic`` watchdog will be used if available, but ignored if it is not. When ``required`` the node will not become a leader unless watchdog can be successfully enabled.
+-  **device**: Path to watchdog device. Defaults to ``/dev/watchdog``.
+-  **safety_margin**: Number of seconds of safety margin between watchdog triggering and leader key expiration.
+
+.. _tags_settings:
+
+Tags
+----
+-  **nofailover**: ``true`` or ``false``, controls whether this node is allowed to participate in the leader race and become a leader. Defaults to ``false``
+-  **clonefrom**: ``true`` or ``false``. If set to ``true`` other nodes might prefer to use this node for bootstrap (take ``pg_basebackup`` from). If there are several nodes with ``clonefrom`` tag set to ``true`` the node to bootstrap from will be chosen randomly. The default value is ``false``.
+-  **noloadbalance**: ``true`` or ``false``. If set to ``true`` the node will return HTTP Status Code 503 for the ``GET /replica`` REST API health-check and therefore will be excluded from the load-balancing. Defaults to ``false``.
+-  **replicatefrom**: The IP address/hostname of another replica. Used to support cascading replication.
+-  **nosync**: ``true`` or ``false``. If set to ``true`` the node will never be selected as a synchronous replica.
+
+In addition to these predefined tags, you can also add your own ones:
+
+-  **key1**: ``true``
+-  **key2**: ``false``
+-  **key3**: ``1.4``
+-  **key4**: ``"RandomString"``
+
+Tags are visible in the :ref:`REST API <rest_api>` and ``patronictl list`` You can also check for an instance health using these tags. If the tag isn't defined for an instance, or if the respective value doesn't match the querying value, it will return HTTP Status Code 503.

features/Dockerfile

@@ -0,0 +1,94 @@
+# syntax = docker/dockerfile:1.5
+# Used only for running tests using tox, see ../tox.ini
+ARG PG_MAJOR
+ARG PGHOME=/home/postgres
+ARG LC_ALL=C.UTF-8
+ARG LANG=C.UTF-8
+ARG BASE_IMAGE=postgres
+
+FROM ${BASE_IMAGE}:${PG_MAJOR}
+
+ARG PGHOME
+ARG LC_ALL
+ARG LANG
+
+ENV PGHOME="$PGHOME"
+ENV PG_USER="${PG_USER:-postgres}"
+ENV PG_GROUP="${PG_GROUP:-$PG_USER}"
+ENV LC_ALL="$LC_ALL"
+ENV LANG="$LANG"
+
+ARG ETCDVERSION=3.3.13
+ENV ETCDVERSION="$ETCDVERSION"
+ARG ETCDURL="https://github.com/coreos/etcd/releases/download/v$ETCDVERSION"
+
+USER root
+RUN set -ex \
+    && apt-get update \
+    && apt-get reinstall init-system-helpers \
+    && apt-get install -y \
+      python3-pip \
+      python3-dev \
+      rsync \
+      curl \
+      gcc \
+      golang \
+      jq  \
+      locales  \
+      sudo \
+      busybox \
+      net-tools \
+      iputils-ping \
+    && rm -rf /var/cache/apt \
+    && python3 -m pip install --no-cache-dir tox \
+    \
+    && mkdir -p "$PGHOME" \
+    && sed -i "s|/var/lib/postgresql.*|$PGHOME:/bin/bash|" /etc/passwd \
+    && chown -R "$PG_USER:$PG_GROUP" /var/log /home/postgres \
+    \
+    # Download etcd \
+    && curl -sL "$ETCDURL/etcd-v$ETCDVERSION-linux-$(dpkg --print-architecture).tar.gz" \
+       | tar xz -C /usr/local/bin --strip=1 --wildcards --no-anchored etcd etcdctl
+
+
+# This Dockerfile syntax only works with docker buildx and the syntax
+# line at the top of this file.
+COPY <<EOF /tox-wrapper.sh
+#!/usr/bin/env bash
+set -ex
+copy_output() {
+    if [[ -d "\$PGHOME/src/features/output" && /src/features ]] ;then
+        cp -a "\$PGHOME/src/features/output" "/src/features/output-\$HOSTNAME"
+        find "/src/features/output-\$HOSTNAME" -type f -exec chmod 666 {} \\;
+        find "/src/features/output-\$HOSTNAME" -type d -exec chmod 777 {} \\;
+    fi
+}
+
+# Ensure the copy is ran if the container is stopped with `docker stop` or `docker kill`
+trap 'copy_output' SIGTERM
+# For architectures such as aarch we need to get the respective GOARCH
+# so we can tell etcd we're ok with running an unsupported architecture.
+export ETCD_UNSUPPORTED_ARCH=$(go env GOARCH)
+cd /src
+runuser -u "\$PG_USER" -- \\
+    find . ! -readable 2>/dev/null \\
+    | sed 's|^./||' >/tmp/copy_exclude.lst \\
+    || true
+runuser -u "\$PG_USER" -- \\
+    rsync -a \\
+    --exclude=.tox \\
+    --exclude="features/output*" \\
+    --exclude-from="/tmp/copy_exclude.lst" \\
+    . "\$PGHOME/src/"
+cd "\$PGHOME/src"
+runuser -u "\$PG_USER" -w ETCD_UNSUPPORTED_ARCH -- "\$@" &
+wait $!
+# SIGINT whilst child proc is running is not seen by trap so we run a copy here instead of using
+# trap copy_output SIGINT EXIT
+copy_output
+EOF
+RUN chmod +x /tox-wrapper.sh
+
+VOLUME /src
+
+ENTRYPOINT ["/tox-wrapper.sh"]

features/basic_replication.feature

@@ -72,14 +72,14 @@ Feature: basic replication
     Then table bar is present on postgres1 after 20 seconds
     And Response on GET http://127.0.0.1:8010/config contains master_start_timeout after 10 seconds
 
-  Scenario: check immediate failover when master_start_timeout=0
-    Given I kill postmaster on postgres2
-    Then postgres1 is a leader after 10 seconds
-    And postgres1 role is the primary after 10 seconds
-
   Scenario: check rejoin of the former primary with pg_rewind
     Given I add the table splitbrain to postgres0
     And I start postgres0
     Then postgres0 role is the secondary after 20 seconds
-    When I add the table buz to postgres1
+    When I add the table buz to postgres2
     Then table buz is present on postgres0 after 20 seconds
+
+  @reject-duplicate-name
+  Scenario: check graceful rejection when two nodes have the same name
+    Given I start duplicate postgres0 on port 8011
+    Then there is a "Can't start; there is already a node named 'postgres0' running" CRITICAL in the dup-postgres0 patroni log

features/citus.feature

@@ -10,20 +10,21 @@ Feature: citus
     And I start postgres3 in citus group 1
     Then replication works from postgres0 to postgres1 after 15 seconds
     Then replication works from postgres2 to postgres3 after 15 seconds
-    And postgres0 is registered in the postgres0 as the worker in group 0
-    And postgres2 is registered in the postgres0 as the worker in group 1
+    And postgres0 is registered in the postgres0 as the primary in group 0 after 5 seconds
+    And postgres2 is registered in the postgres0 as the primary in group 1 after 5 seconds
 
   Scenario: coordinator failover updates pg_dist_node
     Given I run patronictl.py failover batman --group 0 --candidate postgres1 --force
     Then postgres1 role is the primary after 10 seconds
+    And "members/postgres0" key in a group 0 in DCS has state=running after 15 seconds
     And replication works from postgres1 to postgres0 after 15 seconds
+    And postgres1 is registered in the postgres2 as the primary in group 0 after 5 seconds
     And "sync" key in a group 0 in DCS has sync_standby=postgres0 after 15 seconds
-    And postgres1 is registered in the postgres2 as the worker in group 0
-    When I run patronictl.py failover batman --group 0 --candidate postgres0 --force
+    When I run patronictl.py switchover batman --group 0 --candidate postgres0 --force
     Then postgres0 role is the primary after 10 seconds
     And replication works from postgres0 to postgres1 after 15 seconds
+    And postgres0 is registered in the postgres2 as the primary in group 0 after 5 seconds
     And "sync" key in a group 0 in DCS has sync_standby=postgres1 after 15 seconds
-    And postgres0 is registered in the postgres2 as the worker in group 0
 
   Scenario: worker switchover doesn't break client queries on the coordinator
     Given I create a distributed table on postgres0
@@ -31,16 +32,17 @@ Feature: citus
     When I run patronictl.py switchover batman --group 1 --force
     Then I receive a response returncode 0
     And postgres3 role is the primary after 10 seconds
+    And "members/postgres2" key in a group 1 in DCS has state=running after 15 seconds
     And replication works from postgres3 to postgres2 after 15 seconds
+    And postgres3 is registered in the postgres0 as the primary in group 1 after 5 seconds
     And "sync" key in a group 1 in DCS has sync_standby=postgres2 after 15 seconds
-    And postgres3 is registered in the postgres0 as the worker in group 1
     And a thread is still alive
     When I run patronictl.py switchover batman --group 1 --force
     Then I receive a response returncode 0
     And postgres2 role is the primary after 10 seconds
     And replication works from postgres2 to postgres3 after 15 seconds
+    And postgres2 is registered in the postgres0 as the primary in group 1 after 5 seconds
     And "sync" key in a group 1 in DCS has sync_standby=postgres3 after 15 seconds
-    And postgres2 is registered in the postgres0 as the worker in group 1
     And a thread is still alive
     When I stop a thread
     Then a distributed table on postgres0 has expected rows
@@ -52,7 +54,7 @@ Feature: citus
     Then I receive a response returncode 0
     And postgres2 role is the primary after 10 seconds
     And replication works from postgres2 to postgres3 after 15 seconds
-    And postgres2 is registered in the postgres0 as the worker in group 1
+    And postgres2 is registered in the postgres0 as the primary in group 1 after 5 seconds
     And a thread is still alive
     When I stop a thread
     Then a distributed table on postgres0 has expected rows
@@ -64,8 +66,7 @@ Feature: citus
     When I run patronictl.py edit-config batman --group 2 -s ttl=20 --force
     Then I receive a response returncode 0
     And I receive a response output "+ttl: 20"
-    When I sleep for 2 seconds
-    Then postgres4 is registered in the postgres2 as the worker in group 2
+    Then postgres4 is registered in the postgres2 as the primary in group 2 after 5 seconds
     When I shut down postgres4
     Then There is a transaction in progress on postgres0 changing pg_dist_node
     When I run patronictl.py restart batman postgres2 --group 1 --force

features/environment.py

@@ -7,6 +7,7 @@ import psutil
 import re
 import shutil
 import signal
+import stat
 import subprocess
 import sys
 import tempfile
@@ -51,15 +52,14 @@ class AbstractController(abc.ABC):
         self._log = open(os.path.join(self._output_dir, self._name + '.log'), 'a')
         self._handle = self._start()
 
-        assert self._has_started(), "Process {0} is not running after being started".format(self._name)
-
         max_wait_limit *= self._context.timeout_multiplier
         for _ in range(max_wait_limit):
+            assert self._has_started(), "Process {0} is not running after being started".format(self._name)
             if self._is_accessible():
                 break
             time.sleep(1)
         else:
-            assert False,\
+            assert False, \
                 "{0} instance is not available for queries after {1} seconds".format(self._name, max_wait_limit)
 
     def stop(self, kill=False, timeout=15, _=False):
@@ -191,7 +191,7 @@ class PatroniController(AbstractController):
             config['raft'] = {'data_dir': self._output_dir, 'self_addr': 'localhost:' + os.environ['RAFT_PORT']}
 
         host = config['restapi']['listen'].rsplit(':', 1)[0]
-        config['restapi']['listen'] = config['restapi']['connect_address'] = '{0}:{1}'.format(host, 8008+int(name[-1]))
+        config['restapi']['listen'] = config['restapi']['connect_address'] = '{}:{}'.format(host, 8008 + int(name[-1]))
 
         host = config['postgresql']['listen'].rsplit(':', 1)[0]
         config['postgresql']['listen'] = config['postgresql']['connect_address'] = '{0}:{1}'.format(host, self.__PORT)
@@ -251,9 +251,9 @@ class PatroniController(AbstractController):
                         'parameters': {
                             'wal_keep_segments': 100,
                             'archive_mode': 'on',
-                            'archive_command': (PatroniPoolController.ARCHIVE_RESTORE_SCRIPT +
-                                                ' --mode archive ' +
-                                                '--dirname {} --filename %f --pathname %p').format(
+                            'archive_command': (PatroniPoolController.ARCHIVE_RESTORE_SCRIPT
+                                                + ' --mode archive '
+                                                + '--dirname {} --filename %f --pathname %p').format(
                                                     os.path.join(self._work_directory, 'data', 'wal_archive'))
                         }
                     }
@@ -343,6 +343,13 @@ class PatroniController(AbstractController):
                         '--datadir=' + os.path.join(self._work_directory, dest),
                         '--dbname=' + self.backup_source])
 
+    def read_patroni_log(self, level):
+        try:
+            with open(str(os.path.join(self._output_dir or '', self._name + ".log"))) as f:
+                return [line for line in f.readlines() if line[24:24 + len(level)] == level]
+        except IOError:
+            return []
+
 
 class ProcessHang(object):
 
@@ -594,7 +601,7 @@ class KubernetesController(AbstractExternalDcsController):
                 api_process = 'kube-apiserver'
             elif context.startswith('k3d-'):
                 container = '{0}-server-0'.format(context)
-                api_process = 'k3s'
+                api_process = 'k3s server'
             else:
                 return super(KubernetesController, self)._is_running()
             try:
@@ -801,7 +808,7 @@ class PatroniPoolController(object):
             raise Exception  # this one should never happen because the previous line will always raise and exception
         except Exception as e:
             self._context.postgres_supports_ssl = isinstance(e, subprocess.CalledProcessError)\
-                    and 'SSL is not supported by this build' not in e.output.decode()
+                and 'SSL is not supported by this build' not in e.output.decode()
 
     @property
     def patroni_path(self):
@@ -826,7 +833,7 @@ class PatroniPoolController(object):
 
     def __getattr__(self, func):
         if func not in ['stop', 'query', 'write_label', 'read_label', 'check_role_has_changed_to',
-                        'add_tag_to_config', 'get_watchdog', 'patroni_hang', 'backup']:
+                        'add_tag_to_config', 'get_watchdog', 'patroni_hang', 'backup', 'read_patroni_log']:
             raise AttributeError("PatroniPoolController instance has no attribute '{0}'".format(func))
 
         def wrapper(name, *args, **kwargs):
@@ -853,8 +860,8 @@ class PatroniPoolController(object):
             'bootstrap': {
                 'method': 'pg_basebackup',
                 'pg_basebackup': {
-                    'command': " ".join(self.BACKUP_SCRIPT +
-                                        ['--walmethod=stream', '--dbname="{0}"'.format(f.backup_source)])
+                    'command': " ".join(self.BACKUP_SCRIPT
+                                        + ['--walmethod=stream', '--dbname="{0}"'.format(f.backup_source)])
                 },
                 'dcs': {
                     'postgresql': {
@@ -867,9 +874,9 @@ class PatroniPoolController(object):
             'postgresql': {
                 'parameters': {
                     'archive_mode': 'on',
-                    'archive_command': (self.ARCHIVE_RESTORE_SCRIPT + ' --mode archive ' +
-                                        '--dirname {} --filename %f --pathname %p').format(
-                                        os.path.join(self.patroni_path, 'data', 'wal_archive_clone').replace('\\', '/'))
+                    'archive_command': (self.ARCHIVE_RESTORE_SCRIPT + ' --mode archive '
+                                        + '--dirname {} --filename %f --pathname %p')
+                    .format(os.path.join(self.patroni_path, 'data', 'wal_archive_clone').replace('\\', '/'))
                 },
                 'authentication': {
                     'superuser': {'password': 'zalando1'},
@@ -885,13 +892,13 @@ class PatroniPoolController(object):
             'bootstrap': {
                 'method': 'backup_restore',
                 'backup_restore': {
-                    'command': (self.BACKUP_RESTORE_SCRIPT + ' --sourcedir=' +
-                                os.path.join(self.patroni_path, 'data', 'basebackup').replace('\\', '/')),
+                    'command': (self.BACKUP_RESTORE_SCRIPT + ' --sourcedir='
+                                + os.path.join(self.patroni_path, 'data', 'basebackup').replace('\\', '/')),
                     'recovery_conf': {
                         'recovery_target_action': 'promote',
                         'recovery_target_timeline': 'latest',
-                        'restore_command': (self.ARCHIVE_RESTORE_SCRIPT + ' --mode restore ' +
-                                            '--dirname {} --filename %f --pathname %p').format(
+                        'restore_command': (self.ARCHIVE_RESTORE_SCRIPT + ' --mode restore '
+                                            + '--dirname {} --filename %f --pathname %p').format(
                             os.path.join(self.patroni_path, 'data', 'wal_archive_clone').replace('\\', '/'))
                     }
                 }
@@ -910,14 +917,14 @@ class PatroniPoolController(object):
             'scope': cluster_name,
             'postgresql': {
                 'recovery_conf': {
-                    'restore_command': (self.ARCHIVE_RESTORE_SCRIPT + ' --mode restore ' +
-                                        '--dirname {} --filename %f --pathname %p').format(
-                                        os.path.join(self.patroni_path, 'data', 'wal_archive').replace('\\', '/'))
+                    'restore_command': (self.ARCHIVE_RESTORE_SCRIPT + ' --mode restore '
+                                        + '--dirname {} --filename %f --pathname %p')
+                    .format(os.path.join(self.patroni_path, 'data', 'wal_archive').replace('\\', '/'))
                 },
                 'create_replica_methods': ['no_leader_bootstrap'],
                 'no_leader_bootstrap': {
-                    'command': (self.BACKUP_RESTORE_SCRIPT + ' --sourcedir=' +
-                                os.path.join(self.patroni_path, 'data', 'basebackup').replace('\\', '/')),
+                    'command': (self.BACKUP_RESTORE_SCRIPT + ' --sourcedir='
+                                + os.path.join(self.patroni_path, 'data', 'basebackup').replace('\\', '/')),
                     'no_leader': '1'
                 }
             }
@@ -1060,9 +1067,11 @@ def before_all(context):
     try:
         with open(os.devnull, 'w') as null:
             ret = subprocess.call(['openssl', 'req', '-nodes', '-new', '-x509', '-subj', '/CN=batman.patroni',
-                                   '-keyout', context.keyfile, '-out', context.certfile], stdout=null, stderr=null)
+                                   '-addext', 'subjectAltName=IP:127.0.0.1', '-keyout', context.keyfile,
+                                   '-out', context.certfile], stdout=null, stderr=null)
             if ret != 0:
                 raise Exception
+            os.chmod(context.keyfile, stat.S_IWRITE | stat.S_IREAD)
     except Exception:
         context.keyfile = context.certfile = None
 
@@ -1073,7 +1082,9 @@ def before_all(context):
                            'PATRONI_RESTAPI_CERTFILE': context.certfile,
                            'PATRONI_RESTAPI_KEYFILE': context.keyfile,
                            'PATRONI_RESTAPI_VERIFY_CLIENT': 'required',
-                           'PATRONI_CTL_INSECURE': 'on'})
+                           'PATRONI_CTL_INSECURE': 'on',
+                           'PATRONI_CTL_CERTFILE': context.certfile,
+                           'PATRONI_CTL_KEYFILE': context.keyfile})
         ctl.update({'cacert': context.certfile, 'certfile': context.certfile, 'keyfile': context.keyfile})
     context.request_executor = PatroniRequest({'ctl': ctl}, True)
     context.dcs_ctl = context.pctl.known_dcs[context.pctl.dcs](context)
@@ -1135,3 +1146,5 @@ def before_scenario(context, scenario):
                 break
     if 'dcs-failsafe' in scenario.effective_tags and not context.dcs_ctl._handle:
         scenario.skip('it is not possible to control state of {0} from tests'.format(context.dcs_ctl.name()))
+    if 'reject-duplicate-name' in scenario.effective_tags and context.dcs_ctl.name() == 'raft':
+        scenario.skip('Flaky test with Raft')

features/ignored_slots.feature

@@ -10,7 +10,7 @@ Feature: ignored slots
     When I shut down postgres1
     And I start postgres1
     Then postgres1 is a leader after 10 seconds
-    And "members/postgres1" key in DCS has role=master after 3 seconds
+    And "members/postgres1" key in DCS has role=master after 10 seconds
     # Make sure Patroni has finished telling Postgres it should be accepting writes.
     And postgres1 role is the primary after 20 seconds
     # 1. Create our test logical replication slot.
@@ -31,19 +31,19 @@ Feature: ignored slots
     And postgres1 has a logical replication slot named unmanaged_slot_3 with the test_decoding plugin
 
     When I start postgres0
-    Then "members/postgres0" key in DCS has role=replica after 3 seconds
+    Then "members/postgres0" key in DCS has role=replica after 10 seconds
     And postgres0 role is the secondary after 20 seconds
     # Verify that the replica has advanced beyond the point in the WAL
     # where we created the replication slot so that on the next failover
     # cycle we don't accidentally rewind to before the slot creation.
     And replication works from postgres1 to postgres0 after 20 seconds
     When I shut down postgres1
-    Then "members/postgres0" key in DCS has role=master after 3 seconds
+    Then "members/postgres0" key in DCS has role=master after 10 seconds
 
     # 2. After a failover the server (now a replica) still has the slot.
     When I start postgres1
     Then postgres1 role is the secondary after 20 seconds
-    And "members/postgres1" key in DCS has role=replica after 3 seconds
+    And "members/postgres1" key in DCS has role=replica after 10 seconds
     # give Patroni time to sync replication slots
     And I sleep for 2 seconds
     And postgres1 has a logical replication slot named unmanaged_slot_0 with the test_decoding plugin
@@ -54,7 +54,7 @@ Feature: ignored slots
 
     # 3. After a failover the server (now a primary) still has the slot.
     When I shut down postgres0
-    Then "members/postgres1" key in DCS has role=master after 3 seconds
+    Then "members/postgres1" key in DCS has role=master after 10 seconds
     And postgres1 has a logical replication slot named unmanaged_slot_0 with the test_decoding plugin
     And postgres1 has a logical replication slot named unmanaged_slot_1 with the test_decoding plugin
     And postgres1 has a logical replication slot named unmanaged_slot_2 with the test_decoding plugin

features/patroni_api.feature

@@ -35,30 +35,30 @@ Scenario: check local configuration reload
 	Then I receive a response code 202
 
 Scenario: check dynamic configuration change via DCS
-	Given I run patronictl.py edit-config -s 'ttl=10' -p 'max_connections=101' --force batman
-	Then I receive a response returncode 0
-	And I receive a response output "+ttl: 10"
+	Given I issue a PATCH request to http://127.0.0.1:8008/config with {"ttl": 20, "postgresql": {"parameters": {"max_connections": "101"}}}
+	Then I receive a response code 200
 	And Response on GET http://127.0.0.1:8008/patroni contains pending_restart after 11 seconds
 	When I issue a GET request to http://127.0.0.1:8008/config
 	Then I receive a response code 200
-	And I receive a response ttl 10
+	And I receive a response ttl 20
 	When I issue a GET request to http://127.0.0.1:8008/patroni
 	Then I receive a response code 200
 	And I receive a response tags {'new_tag': 'new_value'}
 	And I sleep for 4 seconds
 
 Scenario: check the scheduled restart
-	Given I issue a PATCH request to http://127.0.0.1:8008/config with {"postgresql": {"parameters": {"superuser_reserved_connections": "6"}}}
-	Then I receive a response code 200
-		And Response on GET http://127.0.0.1:8008/patroni contains pending_restart after 5 seconds
+	Given I run patronictl.py edit-config -p 'superuser_reserved_connections=6' --force batman
+	Then I receive a response returncode 0
+	And I receive a response output "+    superuser_reserved_connections: 6"
+	And Response on GET http://127.0.0.1:8008/patroni contains pending_restart after 5 seconds
 	Given I issue a scheduled restart at http://127.0.0.1:8008 in 5 seconds with {"role": "replica"}
 	Then I receive a response code 202
-		And I sleep for 8 seconds
-		And Response on GET http://127.0.0.1:8008/patroni contains pending_restart after 10 seconds
+	And I sleep for 8 seconds
+	And Response on GET http://127.0.0.1:8008/patroni contains pending_restart after 10 seconds
 	Given I issue a scheduled restart at http://127.0.0.1:8008 in 5 seconds with {"restart_pending": "True"}
 	Then I receive a response code 202
-		And Response on GET http://127.0.0.1:8008/patroni does not contain pending_restart after 10 seconds
-		And postgres0 role is the primary after 10 seconds
+	And Response on GET http://127.0.0.1:8008/patroni does not contain pending_restart after 10 seconds
+	And postgres0 role is the primary after 10 seconds
 
 Scenario: check API requests for the primary-replica pair in the pause mode
 	Given I start postgres1
@@ -68,6 +68,7 @@ Scenario: check API requests for the primary-replica pair in the pause mode
 	When I kill postmaster on postgres1
 	And I issue a GET request to http://127.0.0.1:8009/replica
 	Then I receive a response code 503
+	And "members/postgres1" key in DCS has state=stopped after 10 seconds
 	When I run patronictl.py restart batman postgres1 --force
 	Then I receive a response returncode 0
 	Then replication works from postgres0 to postgres1 after 20 seconds
@@ -76,15 +77,15 @@ Scenario: check API requests for the primary-replica pair in the pause mode
 	Then I receive a response code 200
 	And I receive a response state running
 	And I receive a response role replica
-	When I run patronictl.py reinit batman postgres1 --force
+	When I run patronictl.py reinit batman postgres1 --force --wait
 	Then I receive a response returncode 0
 	And I receive a response output "Success: reinitialize for member postgres1"
+	And postgres1 role is the secondary after 30 seconds
+	And replication works from postgres0 to postgres1 after 20 seconds
 	When I run patronictl.py restart batman postgres0 --force
 	Then I receive a response returncode 0
 	And I receive a response output "Success: restart on member postgres0"
 	And postgres0 role is the primary after 5 seconds
-	When I sleep for 10 seconds
-	Then postgres1 role is the secondary after 15 seconds
 
 Scenario: check the switchover via the API in the pause mode
 	Given I issue a POST request to http://127.0.0.1:8008/switchover with {"leader": "postgres0", "candidate": "postgres1"}

features/recovery.feature

@@ -0,0 +1,24 @@
+Feature: recovery
+  We want to check that crashed postgres is started back
+
+  Scenario: check that timeline is not incremented when primary is started after crash
+    Given I start postgres0
+    Then postgres0 is a leader after 10 seconds
+    And there is a non empty initialize key in DCS after 15 seconds
+    When I start postgres1
+    And I add the table foo to postgres0
+    Then table foo is present on postgres1 after 20 seconds
+    When I kill postmaster on postgres0
+    Then postgres0 role is the primary after 10 seconds
+    When I issue a GET request to http://127.0.0.1:8008/
+    Then I receive a response code 200
+    And I receive a response role master
+    And I receive a response timeline 1
+
+  Scenario: check immediate failover when master_start_timeout=0
+    Given I issue a PATCH request to http://127.0.0.1:8008/config with {"master_start_timeout": 0}
+    Then I receive a response code 200
+    And Response on GET http://127.0.0.1:8008/config contains master_start_timeout after 10 seconds
+    When I kill postmaster on postgres0
+    Then postgres1 is a leader after 10 seconds
+    And postgres1 role is the primary after 10 seconds

features/standby_cluster.feature

@@ -13,6 +13,10 @@ Feature: standby cluster
     When I start postgres0
     Then "members/postgres0" key in DCS has state=running after 10 seconds
     And replication works from postgres1 to postgres0 after 15 seconds
+    When I issue a GET request to http://127.0.0.1:8008/patroni
+    Then I receive a response code 200
+    And I receive a response replication_state streaming
+    And "members/postgres0" key in DCS has replication_state=streaming after 10 seconds
 
   @slot-advance
   Scenario: check permanent logical slots are synced to the replica
@@ -34,6 +38,9 @@ Feature: standby cluster
     Then postgres1 is a leader of batman1 after 10 seconds
     When I add the table foo to postgres0
     Then table foo is present on postgres1 after 20 seconds
+    When I issue a GET request to http://127.0.0.1:8009/patroni
+    Then I receive a response code 200
+    And I receive a response replication_state streaming
     And I sleep for 3 seconds
     When I issue a GET request to http://127.0.0.1:8009/primary
     Then I receive a response code 503
@@ -44,6 +51,9 @@ Feature: standby cluster
     When I start postgres2 in a cluster batman1
     Then postgres2 role is the replica after 24 seconds
     And table foo is present on postgres2 after 20 seconds
+    When I issue a GET request to http://127.0.0.1:8010/patroni
+    Then I receive a response code 200
+    And I receive a response replication_state streaming
     And postgres1 does not have a logical replication slot named test_logical
 
   Scenario: check failover

features/steps/basic_replication.py

@@ -9,6 +9,22 @@ def start_patroni(context, name):
     return context.pctl.start(name)
 
 
+@step('I start duplicate {name:w} on port {port:d}')
+def start_duplicate_patroni(context, name, port):
+    config = {
+        "name": name,
+        "restapi": {
+            "listen": "127.0.0.1:{0}".format(port)
+        }
+    }
+    try:
+        context.pctl.start('dup-' + name, custom_config=config)
+        assert False, "Process was expected to fail"
+    except AssertionError as e:
+        assert 'is not running after being started' in str(e), \
+            "No error was raised by duplicate start of {0} ".format(name)
+
+
 @step('I shut down {name:w}')
 def stop_patroni(context, name):
     return context.pctl.stop(name, timeout=60)
@@ -38,7 +54,7 @@ def toggle_wal_replay(context, action, pg_name):
     # pause or resume the wal replay process
     try:
         version = context.pctl.query(pg_name, "SHOW server_version_num").fetchone()[0]
-        wal_name = 'xlog' if int(version)/10000 < 10 else 'wal'
+        wal_name = 'xlog' if int(version) / 10000 < 10 else 'wal'
         context.pctl.query(pg_name, "SELECT pg_{0}_replay_{1}()".format(wal_name, action))
     except pg.Error as e:
         assert False, "Error during {0} wal recovery on {1}: {2}".format(action, pg_name, e)
@@ -72,14 +88,14 @@ def table_is_present_on(context, table_name, pg_name, max_replication_delay):
             break
         sleep(1)
     else:
-        assert False,\
+        assert False, \
             "Table {0} is not present on {1} after {2} seconds".format(table_name, pg_name, max_replication_delay)
 
 
 @then('{pg_name:w} role is the {pg_role:w} after {max_promotion_timeout:d} seconds')
 def check_role(context, pg_name, pg_role, max_promotion_timeout):
     max_promotion_timeout *= context.timeout_multiplier
-    assert context.pctl.check_role_has_changed_to(pg_name, pg_role, timeout=int(max_promotion_timeout)),\
+    assert context.pctl.check_role_has_changed_to(pg_name, pg_role, timeout=int(max_promotion_timeout)), \
         "{0} role didn't change to {1} after {2} seconds".format(pg_name, pg_role, max_promotion_timeout)
 
 
@@ -90,3 +106,10 @@ def replication_works(context, primary, replica, time_limit):
         When I add the table test_{0} to {1}
         Then table test_{0} is present on {2} after {3} seconds
     """.format(int(time()), primary, replica, time_limit))
+
+
+@then('there is a "{message}" {level:w} in the {node} patroni log')
+def check_patroni_log(context, message, level, node):
+    messsages_of_level = context.pctl.read_patroni_log(node, level)
+    assert any(message in line for line in messsages_of_level), \
+        "There was no {0} {1} in the {2} patroni log".format(message, level, node)

features/steps/citus.py

@@ -35,7 +35,7 @@ def check_group_member(context, name, group, key, value, time_limit):
         except Exception:
             pass
         time.sleep(1)
-    assert False, ("{0} in a group {1} does not have {2}={3} (found {4}) in dcs" +
+    assert False, ("{0} in a group {1} does not have {2}={3} (found {4}) in dcs"
                    " after {5} seconds").format(name, group, key, value, response, time_limit)
 
 
@@ -44,12 +44,24 @@ def start_citus(context, name, group):
     return context.pctl.start(name, custom_config={"citus": {"database": "postgres", "group": int(group)}})
 
 
-@step('{name1:w} is registered in the {name2:w} as the worker in group {group:d}')
-def check_registration(context, name1, name2, group):
+@step('{name1:w} is registered in the {name2:w} as the {role:w} in group {group:d} after {time_limit:d} seconds')
+def check_registration(context, name1, name2, role, group, time_limit):
+    time_limit *= context.timeout_multiplier
+    max_time = time.time() + int(time_limit)
+
     worker_port = int(context.pctl.query(name1, "SHOW port").fetchone()[0])
-    r = context.pctl.query(name2, "SELECT nodeport FROM pg_catalog.pg_dist_node WHERE groupid = {0}".format(group))
-    assert worker_port == r.fetchone()[0],\
-        "Worker {0} is not registered in pg_dist_node on the coordinator {1}".format(name1, name2)
+
+    while time.time() < max_time:
+        try:
+            cur = context.pctl.query(name2, "SELECT nodeport, noderole"
+                                            " FROM pg_catalog.pg_dist_node WHERE groupid = {0}".format(group))
+            mapping = {r[0]: r[1] for r in cur}
+            if mapping.get(worker_port) == role:
+                return
+        except Exception:
+            pass
+        time.sleep(1)
+    assert False, "Node {0} is not registered in pg_dist_node on the node {1}".format(name1, name2)
 
 
 @step('I create a distributed table on {name:w}')
@@ -93,7 +105,7 @@ def thread_is_alive(context):
 @step("I stop a thread")
 def stop_insert_thread(context):
     context.thread_stop_event.set()
-    context.thread.join(1*context.timeout_multiplier)
+    context.thread.join(1 * context.timeout_multiplier)
     assert not context.thread.is_alive(), "Thread is still alive"
 
 
@@ -113,5 +125,5 @@ def check_transaction(context, name):
 
 @step("a transaction finishes in {timeout:d} seconds")
 def check_transaction_timeout(context, timeout):
-    assert (datetime.now(tzutc) - context.xact_start).seconds > timeout,\
-            "a transaction finished earlier than in {0} seconds".format(timeout)
+    assert (datetime.now(tzutc) - context.xact_start).seconds > timeout, \
+        "a transaction finished earlier than in {0} seconds".format(timeout)

features/steps/patroni_api.py

@@ -98,7 +98,7 @@ def do_run(context, cmd):
 @then('I receive a response {component:w} {data}')
 def check_response(context, component, data):
     if component == 'code':
-        assert context.status_code == int(data),\
+        assert context.status_code == int(data), \
             "status code {0} != {1}, response: {2}".format(context.status_code, data, context.response)
     elif component == 'returncode':
         assert context.status_code == int(data), "return code {0} != {1}, {2}".format(context.status_code,
@@ -158,7 +158,7 @@ def check_http_response(context, url, value, timeout, negate=False):
             break
         time.sleep(1)
     else:
-        assert False,\
+        assert False, \
             "Value {0} is {1} present in response after {2} seconds".format(value, "not" if not negate else "", timeout)
 
 

features/steps/standby_cluster.py

@@ -16,8 +16,8 @@ def start_patroni(context, name, cluster_name):
         "postgresql": {
             "callbacks": callbacks(context, name),
             "backup_restore": {
-                "command": (context.pctl.PYTHON + " features/backup_restore.py --sourcedir=" +
-                            os.path.join(context.pctl.patroni_path, 'data', 'basebackup').replace('\\', '/'))}
+                "command": (context.pctl.PYTHON + " features/backup_restore.py --sourcedir="
+                            + os.path.join(context.pctl.patroni_path, 'data', 'basebackup').replace('\\', '/'))}
         }
     })
 

kubernetes/Dockerfile.citus

@@ -7,11 +7,13 @@ RUN export DEBIAN_FRONTEND=noninteractive \
     && apt-get upgrade -y \
     && apt-cache depends patroni | sed -n -e 's/.* Depends: \(python3-.\+\)$/\1/p' \
             | grep -Ev '^python3-(sphinx|etcd|consul|kazoo|kubernetes)' \
-            | xargs apt-get install -y busybox vim-tiny curl jq less locales git python3-pip python3-wheel \
+            | xargs apt-get install -y busybox vim-tiny curl jq less locales git python3-pip python3-wheel lsb-release \
     ## Make sure we have a en_US.UTF-8 locale available
     && localedef -i en_US -c -f UTF-8 -A /usr/share/locale/locale.alias en_US.UTF-8 \
-    && curl https://install.citusdata.com/community/deb.sh | bash \
-    && apt-get -y install postgresql-15-citus-11.2 \
+    && echo "deb [signed-by=/etc/apt/trusted.gpg.d/citusdata_community.gpg] https://packagecloud.io/citusdata/community/debian/ $(lsb_release -cs) main" > /etc/apt/sources.list.d/citusdata_community.list \
+    && curl -sL https://packagecloud.io/citusdata/community/gpgkey | gpg --dearmor > /etc/apt/trusted.gpg.d/citusdata_community.gpg \
+    && apt-get update -y \
+    && apt-get -y install postgresql-$PG_MAJOR-citus-11.3 \
     && pip3 install setuptools \
     && pip3 install 'git+https://github.com/zalando/patroni.git#egg=patroni[kubernetes]' \
     && PGHOME=/home/postgres \
@@ -32,7 +34,9 @@ ADD entrypoint.sh /
 ENV PGSSLMODE=verify-ca PGSSLKEY=/etc/ssl/private/ssl-cert-snakeoil.key PGSSLCERT=/etc/ssl/certs/ssl-cert-snakeoil.pem PGSSLROOTCERT=/etc/ssl/certs/ssl-cert-snakeoil.pem
 
 RUN sed -i 's/^postgresql:/&\n  basebackup:\n    checkpoint: fast/' /entrypoint.sh \
-    && sed -i "s|^    postgresql:|&\n      pg_hba:\n      - local all all trust\n      - hostssl replication all all md5 clientcert=$PGSSLMODE\n      - hostssl all all all md5 clientcert=$PGSSLMODE\n      parameters:\n        max_connections: 100\n        shared_buffers: 16MB\n        ssl: 'on'\n        ssl_ca_file: $PGSSLROOTCERT\n        ssl_cert_file: $PGSSLCERT\n        ssl_key_file: $PGSSLKEY\n        citus.node_conninfo: 'sslrootcert=$PGSSLROOTCERT sslkey=$PGSSLKEY sslcert=$PGSSLCERT sslmode=$PGSSLMODE'|"  /entrypoint.sh \
+    && sed -i "s|^    postgresql:|&\n      parameters:\n        max_connections: 100\n        shared_buffers: 16MB\n        ssl: 'on'\n        ssl_ca_file: $PGSSLROOTCERT\n        ssl_cert_file: $PGSSLCERT\n        ssl_key_file: $PGSSLKEY\n        citus.node_conninfo: 'sslrootcert=$PGSSLROOTCERT sslkey=$PGSSLKEY sslcert=$PGSSLCERT sslmode=$PGSSLMODE'|"  /entrypoint.sh \
+    && sed -i 's/^      pg_hba:/&\n      - local all all trust/' /entrypoint.sh \
+    && sed -i "s/^\(.*\) \(.*\) \(.*\) \(.*\) \(.*\) md5.*$/\1 hostssl \3 \4 all md5 clientcert=$PGSSLMODE/" /entrypoint.sh \
     && sed -i "s#^    \(superuser\|replication\):#&\n      sslmode: $PGSSLMODE\n      sslkey: $PGSSLKEY\n      sslcert: $PGSSLCERT\n      sslrootcert: $PGSSLROOTCERT#" /entrypoint.sh
 
 EXPOSE 5432 8008

kubernetes/entrypoint.sh

@@ -12,15 +12,15 @@ bootstrap:
   dcs:
     postgresql:
       use_pg_rewind: true
+      pg_hba:
+      - host all all 0.0.0.0/0 md5
+      - host replication ${PATRONI_REPLICATION_USERNAME} ${PATRONI_KUBERNETES_POD_IP}/16 md5
   initdb:
   - auth-host: md5
   - auth-local: trust
   - encoding: UTF8
   - locale: en_US.UTF-8
   - data-checksums
-  pg_hba:
-  - host all all 0.0.0.0/0 md5
-  - host replication ${PATRONI_REPLICATION_USERNAME} ${PATRONI_KUBERNETES_POD_IP}/16 md5
 restapi:
   connect_address: '${PATRONI_KUBERNETES_POD_IP}:8008'
 postgresql:

patroni.spec

@@ -16,7 +16,10 @@ def hiddenimports():
 a = Analysis(['patroni/__main__.py'],
              pathex=[],
              binaries=None,
-             datas=None,
+             datas=[
+                ('patroni/postgresql/available_parameters/*.yml', 'patroni/postgresql/available_parameters'),
+                ('patroni/postgresql/available_parameters/*.yaml', 'patroni/postgresql/available_parameters'),
+            ],
              hiddenimports=hiddenimports(),
              hookspath=[],
              runtime_hooks=[],

patroni/__init__.py

@@ -1,17 +1,54 @@
+"""Define general variables and functions for :mod:`patroni`.
+
+:var PATRONI_ENV_PREFIX: prefix for Patroni related configuration environment variables.
+:var KUBERNETES_ENV_PREFIX: prefix for Kubernetes related configuration environment variables.
+:var MIN_PSYCOPG2: minimum version of :mod:`psycopg2` required by Patroni to work.
+"""
+
 import sys
 
+from typing import Any, Callable, Iterator, Tuple
+
 PATRONI_ENV_PREFIX = 'PATRONI_'
 KUBERNETES_ENV_PREFIX = 'KUBERNETES_'
 MIN_PSYCOPG2 = (2, 5, 4)
 
 
-def fatal(string, *args):
-    sys.stderr.write('FATAL: ' + string.format(*args) + '\n')
-    sys.exit(1)
+def fatal(string: str, *args: Any) -> None:
+    """Write a fatal message to stderr and exit with code ``1``.
+
+    :param string: message to be written before exiting.
+    """
+    sys.exit('FATAL: ' + string.format(*args))
 
 
-def parse_version(version):
-    def _parse_version(version):
+def parse_version(version: str) -> Tuple[int, ...]:
+    """Convert *version* from human-readable format to tuple of integers.
+
+    .. note::
+        Designed for easy comparison of software versions in Python.
+
+    :param version: human-readable software version, e.g. ``2.5.4``.
+
+    :returns: tuple of *version* parts, each part as an integer.
+
+    :Example:
+
+        >>> parse_version('2.5.4')
+        (2, 5, 4)
+    """
+    def _parse_version(version: str) -> Iterator[int]:
+        """Yield each part of a human-readable version string as an integer.
+
+        :param version: human-readable software version, e.g. ``2.5.4``.
+
+        :yields: each part of *version* as an integer.
+
+        :Example:
+
+            >>> tuple(_parse_version('2.5.4'))
+            (2, 5, 4)
+        """
         for e in version.split('.'):
             try:
                 yield int(e)
@@ -20,10 +57,25 @@ def parse_version(version):
     return tuple(_parse_version(version.split(' ')[0]))
 
 
-# We pass MIN_PSYCOPG2 and parse_version as arguments to simplify usage of check_psycopg from the setup.py
-def check_psycopg(_min_psycopg2=MIN_PSYCOPG2, _parse_version=parse_version):
+def check_psycopg(_min_psycopg2: Tuple[int, ...] = MIN_PSYCOPG2,
+                  _parse_version: Callable[[str], Tuple[int, ...]] = parse_version) -> None:
+    """Ensure at least one among :mod:`psycopg2` or :mod:`psycopg` libraries are available in the environment.
+
+    .. note::
+        We pass ``MIN_PSYCOPG2`` and :func:`parse_version` as arguments to simplify usage of :func:`check_psycopg` from
+        the ``setup.py``.
+
+    .. note::
+        Patroni chooses :mod:`psycopg2` over :mod:`psycopg`, if possible.
+
+        If nothing meeting the requirements is found, then exit with a fatal message.
+
+    :param _min_psycopg2: minimum required version in case :mod:`psycopg2` is chosen.
+    :param _parse_version: function used to parse :mod:`psycopg2`/:mod:`psycopg` version into a comparable object.
+    """
     min_psycopg2_str = '.'.join(map(str, _min_psycopg2))
 
+    # try psycopg2
     try:
         from psycopg2 import __version__
         if _parse_version(__version__) >= _min_psycopg2:
@@ -32,10 +84,11 @@ def check_psycopg(_min_psycopg2=MIN_PSYCOPG2, _parse_version=parse_version):
     except ImportError:
         version_str = None
 
+    # try psycopg3
     try:
         from psycopg import __version__
     except ImportError:
         error = 'Patroni requires psycopg2>={0}, psycopg2-binary, or psycopg>=3.0'.format(min_psycopg2_str)
-        if version_str:
+        if version_str is not None:
             error += ', but only psycopg2=={0} is available'.format(version_str)
         fatal(error)

patroni/__main__.py

@@ -1,16 +1,23 @@
 import logging
 import os
 import signal
+import sys
 import time
 
-from patroni.daemon import AbstractPatroniDaemon, abstract_main
+from argparse import Namespace
+from typing import Any, Dict, Optional, TYPE_CHECKING
+
+from patroni.daemon import AbstractPatroniDaemon, abstract_main, get_base_arg_parser
+
+if TYPE_CHECKING:  # pragma: no cover
+    from .config import Config
 
 logger = logging.getLogger(__name__)
 
 
 class Patroni(AbstractPatroniDaemon):
 
-    def __init__(self, config):
+    def __init__(self, config: 'Config') -> None:
         from patroni.api import RestApiServer
         from patroni.dcs import get_dcs
         from patroni.ha import Ha
@@ -23,19 +30,22 @@ class Patroni(AbstractPatroniDaemon):
 
         self.version = __version__
         self.dcs = get_dcs(self.config)
+        self.request = PatroniRequest(self.config, True)
+
+        self.ensure_unique_name()
+
         self.watchdog = Watchdog(self.config)
         self.load_dynamic_configuration()
 
         self.postgresql = Postgresql(self.config['postgresql'])
         self.api = RestApiServer(self, self.config['restapi'])
-        self.request = PatroniRequest(self.config, True)
         self.ha = Ha(self)
 
         self.tags = self.get_tags()
         self.next_run = time.time()
-        self.scheduled_restart = {}
+        self.scheduled_restart: Dict[str, Any] = {}
 
-    def load_dynamic_configuration(self):
+    def load_dynamic_configuration(self) -> None:
         from patroni.exceptions import DCSError
         while True:
             try:
@@ -53,19 +63,41 @@ class Patroni(AbstractPatroniDaemon):
                 logger.warning('Can not get cluster from dcs')
                 time.sleep(5)
 
-    def get_tags(self):
+    def ensure_unique_name(self) -> None:
+        """A helper method to prevent splitbrain from operator naming error."""
+        from urllib.parse import urlparse
+        from urllib3.connection import HTTPConnection
+        from patroni.dcs import Member
+
+        cluster = self.dcs.get_cluster()
+        if not cluster:
+            return
+        member = cluster.get_member(self.config['name'], False)
+        if not isinstance(member, Member):
+            return
+        try:
+            parts = urlparse(member.api_url)
+            if isinstance(parts.hostname, str):
+                connection = HTTPConnection(parts.hostname, port=parts.port or 80, timeout=3)
+                connection.connect()
+                logger.fatal("Can't start; there is already a node named '%s' running", self.config['name'])
+                sys.exit(1)
+        except Exception:
+            return
+
+    def get_tags(self) -> Dict[str, Any]:
         return {tag: value for tag, value in self.config.get('tags', {}).items()
                 if tag not in ('clonefrom', 'nofailover', 'noloadbalance', 'nosync') or value}
 
     @property
-    def nofailover(self):
+    def nofailover(self) -> bool:
         return bool(self.tags.get('nofailover', False))
 
     @property
-    def nosync(self):
+    def nosync(self) -> bool:
         return bool(self.tags.get('nosync', False))
 
-    def reload_config(self, sighup=False, local=False):
+    def reload_config(self, sighup: bool = False, local: Optional[bool] = False) -> None:
         try:
             super(Patroni, self).reload_config(sighup, local)
             if local:
@@ -87,7 +119,7 @@ class Patroni(AbstractPatroniDaemon):
     def noloadbalance(self):
         return bool(self.tags.get('noloadbalance', False))
 
-    def schedule_next_run(self):
+    def schedule_next_run(self) -> None:
         self.next_run += self.dcs.loop_wait
         current_time = time.time()
         nap_time = self.next_run - current_time
@@ -100,12 +132,12 @@ class Patroni(AbstractPatroniDaemon):
         elif self.ha.watch(nap_time):
             self.next_run = time.time()
 
-    def run(self):
+    def run(self) -> None:
         self.api.start()
         self.next_run = time.time()
         super(Patroni, self).run()
 
-    def _run_cycle(self):
+    def _run_cycle(self) -> None:
         logger.info(self.ha.run_cycle())
 
         if self.dcs.cluster and self.dcs.cluster.config and self.dcs.cluster.config.data \
@@ -117,7 +149,7 @@ class Patroni(AbstractPatroniDaemon):
 
         self.schedule_next_run()
 
-    def _shutdown(self):
+    def _shutdown(self) -> None:
         try:
             self.api.shutdown()
         except Exception:
@@ -128,26 +160,47 @@ class Patroni(AbstractPatroniDaemon):
             logger.exception('Exception during Ha.shutdown')
 
 
-def patroni_main():
+def patroni_main(configfile: str) -> None:
     from multiprocessing import freeze_support
-    from patroni.validator import schema
 
     freeze_support()
-    abstract_main(Patroni, schema)
+    abstract_main(Patroni, configfile)
 
 
-def main():
+def process_arguments() -> Namespace:
+    parser = get_base_arg_parser()
+    parser.add_argument('--validate-config', action='store_true', help='Run config validator and exit')
+    args = parser.parse_args()
+
+    if args.validate_config:
+        from patroni.validator import schema
+        from patroni.config import Config, ConfigParseError
+
+        try:
+            Config(args.configfile, validator=schema)
+            sys.exit()
+        except ConfigParseError as e:
+            sys.exit(e.value)
+
+    return args
+
+
+def main() -> None:
+    from patroni import check_psycopg
+
+    args = process_arguments()
+
+    check_psycopg()
+
     if os.getpid() != 1:
-        from patroni import check_psycopg
-
-        check_psycopg()
-        return patroni_main()
+        return patroni_main(args.configfile)
 
     # Patroni started with PID=1, it looks like we are in the container
+    from types import FrameType
     pid = 0
 
     # Looks like we are in a docker, so we will act like init
-    def sigchld_handler(signo, stack_frame):
+    def sigchld_handler(signo: int, stack_frame: Optional[FrameType]) -> None:
         try:
             while True:
                 ret = os.waitpid(-1, os.WNOHANG)
@@ -158,7 +211,7 @@ def main():
         except OSError:
             pass
 
-    def passtochild(signo, stack_frame):
+    def passtochild(signo: int, stack_frame: Optional[FrameType]):
         if pid:
             os.kill(pid, signo)
 
@@ -173,7 +226,7 @@ def main():
     signal.signal(signal.SIGTERM, passtochild)
 
     import multiprocessing
-    patroni = multiprocessing.Process(target=patroni_main)
+    patroni = multiprocessing.Process(target=patroni_main, args=(args.configfile,))
     patroni.start()
     pid = patroni.pid
     patroni.join()

patroni/async_executor.py

@@ -1,5 +1,11 @@
+"""Implement facilities for executing asynchronous tasks."""
 import logging
+
 from threading import Event, Lock, RLock, Thread
+from types import TracebackType
+from typing import Any, Callable, Optional, Tuple, Type
+
+from .postgresql.cancellable import CancellableSubprocess
 
 logger = logging.getLogger(__name__)
 
@@ -8,65 +14,110 @@ class CriticalTask(object):
     """Represents a critical task in a background process that we either need to cancel or get the result of.
 
     Fields of this object may be accessed only when holding a lock on it. To perform the critical task the background
-    thread must, while holding lock on this object, check `is_cancelled` flag, run the task and mark the task as
-    complete using `complete()`.
+    thread must, while holding lock on this object, check ``is_cancelled`` flag, run the task and mark the task as
+    complete using :func:`complete`.
 
     The main thread must hold async lock to prevent the task from completing, hold lock on critical task object,
-    call cancel. If the task has completed `cancel()` will return False and `result` field will contain the result of
-    the task. When cancel returns True it is guaranteed that the background task will notice the `is_cancelled` flag.
+    call :func:`cancel`. If the task has completed :func:`cancel` will return ``False`` and ``result`` field will
+    contain the result of the task. When :func:`cancel` returns ``True`` it is guaranteed that the background task will
+    notice the ``is_cancelled`` flag.
+
+    :ivar is_cancelled: if the critical task has been cancelled.
+    :ivar result: contains the result of the task, if it has already been completed.
     """
-    def __init__(self):
+
+    def __init__(self) -> None:
+        """Create a new instance of :class:`CriticalTask`.
+
+        Instantiate the lock and the task control attributes.
+        """
         self._lock = Lock()
         self.is_cancelled = False
         self.result = None
 
-    def reset(self):
+    def reset(self) -> None:
         """Must be called every time the background task is finished.
 
-        Must be called from async thread. Caller must hold lock on async executor when calling."""
+        .. note::
+            Must be called from async thread. Caller must hold lock on async executor when calling.
+        """
         self.is_cancelled = False
         self.result = None
 
-    def cancel(self):
-        """Tries to cancel the task, returns True if the task has already run.
+    def cancel(self) -> bool:
+        """Tries to cancel the task.
 
-        Caller must hold lock on async executor and the task when calling."""
+        .. note::
+            Caller must hold lock on async executor and the task when calling.
+
+        :returns: ``False`` if the task has already run, or ``True`` it has been cancelled.
+        """
         if self.result is not None:
             return False
         self.is_cancelled = True
         return True
 
-    def complete(self, result):
-        """Mark task as completed along with a result.
+    def complete(self, result: Any) -> None:
+        """Mark task as completed along with a *result*.
 
-        Must be called from async thread. Caller must hold lock on task when calling."""
+        .. note::
+            Must be called from async thread. Caller must hold lock on task when calling.
+        """
         self.result = result
 
-    def __enter__(self):
+    def __enter__(self) -> 'CriticalTask':
+        """Acquire the object lock when entering the context manager."""
         self._lock.acquire()
         return self
 
-    def __exit__(self, exc_type, exc_val, exc_tb):
+    def __exit__(self, exc_type: Optional[Type[BaseException]],
+                 exc_val: Optional[BaseException], exc_tb: Optional[TracebackType]) -> None:
+        """Release the object lock when exiting the context manager."""
         self._lock.release()
 
 
 class AsyncExecutor(object):
+    """Asynchronous executor of (long) tasks.
 
-    def __init__(self, cancellable, ha_wakeup):
+    :ivar critical_task: a :class:`CriticalTask` instance to handle execution of critical background tasks.
+    """
+
+    def __init__(self, cancellable: CancellableSubprocess, ha_wakeup: Callable[..., None]) -> None:
+        """Create a new instance of :class:`AsyncExecutor`.
+
+        Configure the given *cancellable* and *ha_wakeup*, initializes the control attributes, and instantiate the lock
+        and event objects that are used to access attributes and manage communication between threads.
+
+        :param cancellable: a subprocess that supports being cancelled.
+        :param ha_wakeup: function to wake up the HA loop.
+        """
         self._cancellable = cancellable
         self._ha_wakeup = ha_wakeup
         self._thread_lock = RLock()
-        self._scheduled_action = None
+        self._scheduled_action: Optional[str] = None
         self._scheduled_action_lock = RLock()
         self._is_cancelled = False
         self._finish_event = Event()
         self.critical_task = CriticalTask()
 
     @property
-    def busy(self):
+    def busy(self) -> bool:
+        """``True`` if there is an action scheduled to occur, else ``False``."""
         return self.scheduled_action is not None
 
-    def schedule(self, action):
+    def schedule(self, action: str) -> Optional[str]:
+        """Schedule *action* to be executed.
+
+        .. note::
+            Must be called before executing a task.
+
+        .. note::
+            *action* can only be scheduled if there is no other action currently scheduled.
+
+        :param action: action to be executed.
+
+        :returns: ``None`` if *action* has been successfully scheduled, or the previously scheduled action, if any.
+        """
         with self._scheduled_action_lock:
             if self._scheduled_action is not None:
                 return self._scheduled_action
@@ -76,15 +127,33 @@ class AsyncExecutor(object):
         return None
 
     @property
-    def scheduled_action(self):
+    def scheduled_action(self) -> Optional[str]:
+        """The currently scheduled action, if any, else ``None``."""
         with self._scheduled_action_lock:
             return self._scheduled_action
 
-    def reset_scheduled_action(self):
+    def reset_scheduled_action(self) -> None:
+        """Unschedule a previously scheduled action, if any.
+
+        .. note::
+            Must be called once the scheduled task finishes or is cancelled.
+        """
         with self._scheduled_action_lock:
             self._scheduled_action = None
 
-    def run(self, func, args=()):
+    def run(self, func: Callable[..., Any], args: Tuple[Any, ...] = ()) -> Optional[Any]:
+        """Run *func* with *args*.
+
+        .. note::
+            Expected to be executed through a thread.
+
+        :param func: function to be run. If it returns anything other than ``None``, HA loop will be woken up at the end
+            of :func:`run` execution.
+        :param args: arguments to be passed to *func*.
+
+        :returns: ``None`` if *func* execution has been cancelled or faced any exception, otherwise the result of
+            *func*.
+        """
         wakeup = False
         try:
             with self:
@@ -107,16 +176,37 @@ class AsyncExecutor(object):
             if wakeup is not None:
                 self._ha_wakeup()
 
-    def run_async(self, func, args=()):
+    def run_async(self, func: Callable[..., Any], args: Tuple[Any, ...] = ()) -> None:
+        """Start an async thread that runs *func* with *args*.
+
+        :param func: function to be run. Will be passed through args to :class:`~threading.Thread` with a target of
+            :func:`run`.
+        :param args: arguments to be passed along to :class:`~threading.Thread` with *func*.
+
+        """
         Thread(target=self.run, args=(func, args)).start()
 
-    def try_run_async(self, action, func, args=()):
+    def try_run_async(self, action: str, func: Callable[..., Any], args: Tuple[Any, ...] = ()) -> Optional[str]:
+        """Try to run an async task, if none is currently being executed.
+
+        :param action: name of the task to be executed.
+        :param func: actual function that performs the task *action*.
+        :param args: arguments to be passed to *func*.
+
+        :returns: ``None`` if *func* was scheduled successfully, otherwise an error message informing of an already
+            ongoing task.
+        """
         prev = self.schedule(action)
         if prev is None:
             return self.run_async(func, args)
         return 'Failed to run {0}, {1} is already in progress'.format(action, prev)
 
-    def cancel(self):
+    def cancel(self) -> None:
+        """Request cancellation of a scheduled async task, if any.
+
+        .. note::
+            Wait until task is cancelled before returning control to caller.
+        """
         with self:
             with self._scheduled_action_lock:
                 if self._scheduled_action is None:
@@ -130,8 +220,16 @@ class AsyncExecutor(object):
         with self:
             self.reset_scheduled_action()
 
-    def __enter__(self):
+    def __enter__(self) -> 'AsyncExecutor':
+        """Acquire the thread lock when entering the context manager."""
         self._thread_lock.acquire()
+        return self
 
-    def __exit__(self, *args):
+    def __exit__(self, exc_type: Optional[Type[BaseException]],
+                 exc_val: Optional[BaseException], exc_tb: Optional[TracebackType]) -> None:
+        """Release the thread lock when exiting the context manager.
+
+        .. note::
+            The arguments are not used, but we need them to match the expected method signature.
+        """
         self._thread_lock.release()

patroni/collections.py

@@ -0,0 +1,202 @@
+"""Patroni custom object types somewhat like :mod:`collections` module.
+
+Provides a case insensitive :class:`dict` and :class:`set` object types.
+"""
+from collections import OrderedDict
+from typing import Any, Collection, Dict, Iterator, MutableMapping, MutableSet, Optional
+
+
+class CaseInsensitiveSet(MutableSet[str]):
+    """A case-insensitive :class:`set`-like object.
+
+    Implements all methods and operations of :class:`~typing.MutableSet`. All values are expected to be strings.
+    The structure remembers the case of the last value set, however, contains testing is case insensitive.
+    """
+
+    def __init__(self, values: Optional[Collection[str]] = None) -> None:
+        """Create a new instance of :class:`CaseInsensitiveSet` with the given *values*.
+
+        :param values: values to be added to the set.
+        """
+        self._values: Dict[str, str] = {}
+        for v in values or ():
+            self.add(v)
+
+    def __repr__(self) -> str:
+        """Get a string representation of the set.
+
+        Provide a helpful way of recreating the set.
+
+        :returns: representation of the set, showing its values.
+
+        :Example:
+
+            >>> repr(CaseInsensitiveSet(('1', 'test', 'Test', 'TESt', 'test2')))  # doctest: +ELLIPSIS
+            "<CaseInsensitiveSet('1', 'TESt', 'test2') at ..."
+        """
+        return '<{0}{1} at {2:x}>'.format(type(self).__name__, tuple(self._values.values()), id(self))
+
+    def __str__(self) -> str:
+        """Get set values for printing.
+
+        :returns: set of values in string format.
+
+        :Example:
+
+            >>> str(CaseInsensitiveSet(('1', 'test', 'Test', 'TESt', 'test2')))  # doctest: +SKIP
+            "{'TESt', 'test2', '1'}"
+        """
+        return str(set(self._values.values()))
+
+    def __contains__(self, value: str) -> bool:
+        """Check if set contains *value*.
+
+        The check is performed case-insensitively.
+
+        :param value: value to be checked.
+
+        :returns: ``True`` if *value* is already in the set, ``False`` otherwise.
+        """
+        return value.lower() in self._values
+
+    def __iter__(self) -> Iterator[str]:
+        """Iterate over the values in this set.
+
+        :yields: values from set.
+        """
+        return iter(self._values.values())
+
+    def __len__(self) -> int:
+        """Get the length of this set.
+
+        :returns: number of values in the set.
+
+        :Example:
+
+        >>> len(CaseInsensitiveSet(('1', 'test', 'Test', 'TESt', 'test2')))
+        3
+        """
+        return len(self._values)
+
+    def add(self, value: str) -> None:
+        """Add *value* to this set.
+
+        Search is performed case-insensitively. If *value* is already in the set, overwrite it with *value*, so we
+        "remember" the last case of *value*.
+
+        :param value: value to be added to the set.
+        """
+        self._values[value.lower()] = value
+
+    def discard(self, value: str) -> None:
+        """Remove *value* from this set.
+
+        Search is performed case-insensitively. If *value* is not present in the set, no exception is raised.
+
+        :param value: value to be removed from the set.
+        """
+        self._values.pop(value.lower(), None)
+
+    def issubset(self, other: 'CaseInsensitiveSet') -> bool:
+        """Check if this set is a subset of *other*.
+
+        :param other: another set to be compared with this set.
+        :returns: ``True`` if this set is a subset of *other*, else ``False``.
+        """
+        return self <= other
+
+
+class CaseInsensitiveDict(MutableMapping[str, Any]):
+    """A case-insensitive :class:`dict`-like object.
+
+    Implements all methods and operations of :class:`~typing.MutableMapping` as well as :class:`dict`'s
+    :func:`~dict.copy`. All keys are expected to be strings. The structure remembers the case of the last key to be set,
+    and :func:`iter`, :func:`dict.keys`, :func:`dict.items`, :func:`dict.iterkeys`, and :func:`dict.iteritems` will
+    contain case-sensitive keys. However, querying and contains testing is case insensitive.
+    """
+
+    def __init__(self, data: Optional[Dict[str, Any]] = None) -> None:
+        """Create a new instance of :class:`CaseInsensitiveDict` with the given *data*.
+
+        :param data: initial dictionary to create a :class:`CaseInsensitiveDict` from.
+        """
+        self._values: OrderedDict[str, Any] = OrderedDict()
+        self.update(data or {})
+
+    def __setitem__(self, key: str, value: Any) -> None:
+        """Assign *value* to *key* in this dict.
+
+        *key* is searched/stored case-insensitively in the dict. The corresponding value in the dict is a tuple of:
+            * original *key*;
+            * *value*.
+
+        :param key: key to be created or updated in the dict.
+        :param value: value for *key*.
+        """
+        self._values[key.lower()] = (key, value)
+
+    def __getitem__(self, key: str) -> Any:
+        """Get the value corresponding to *key*.
+
+        *key* is searched case-insensitively in the dict.
+
+        .. note:
+            If *key* is not present in the dict, :class:`KeyError` will be triggered.
+
+        :param key: key to be searched in the dict.
+
+        :returns: value corresponding to *key*.
+        """
+        return self._values[key.lower()][1]
+
+    def __delitem__(self, key: str) -> None:
+        """Remove *key* from this dict.
+
+        *key* is searched case-insensitively in the dict.
+
+        .. note:
+            If *key* is not present in the dict, :class:`KeyError` will be triggered.
+
+        :param key: key to be removed from the dict.
+        """
+        del self._values[key.lower()]
+
+    def __iter__(self) -> Iterator[str]:
+        """Iterate over keys of this dict.
+
+        :yields: each key present in the dict. Yields each key with its last case that has been stored.
+        """
+        return iter(key for key, _ in self._values.values())
+
+    def __len__(self) -> int:
+        """Get the length of this dict.
+
+        :returns: number of keys in the dict.
+
+        :Example:
+
+        >>> len(CaseInsensitiveDict({'a': 'b', 'A': 'B', 'c': 'd'}))
+        2
+        """
+        return len(self._values)
+
+    def copy(self) -> 'CaseInsensitiveDict':
+        """Create a copy of this dict.
+
+        :return: a new dict object with the same keys and values of this dict.
+        """
+        return CaseInsensitiveDict({v[0]: v[1] for v in self._values.values()})
+
+    def __repr__(self) -> str:
+        """Get a string representation of the dict.
+
+        Provide a helpful way of recreating the dict.
+
+        :returns: representation of the dict, showing its keys and values.
+
+        :Example:
+
+            >>> repr(CaseInsensitiveDict({'a': 'b', 'A': 'B', 'c': 'd'}))  # doctest: +ELLIPSIS
+            "<CaseInsensitiveDict{'A': 'B', 'c': 'd'} at ..."
+        """
+        return '<{0}{1} at {2:x}>'.format(type(self).__name__, dict(self.items()), id(self))

patroni/config.py

@@ -7,11 +7,16 @@ import yaml
 
 from collections import defaultdict
 from copy import deepcopy
-from patroni import PATRONI_ENV_PREFIX
-from patroni.exceptions import ConfigParseError
-from patroni.dcs import ClusterConfig
-from patroni.postgresql.config import CaseInsensitiveDict, ConfigHandler
-from patroni.utils import deep_compare, parse_bool, parse_int, patch_config
+from typing import Any, Callable, Collection, Dict, List, Optional, Union, TYPE_CHECKING
+
+from . import PATRONI_ENV_PREFIX
+from .collections import CaseInsensitiveDict
+from .dcs import ClusterConfig, Cluster
+from .exceptions import ConfigParseError
+from .file_perm import pg_perm
+from .postgresql.config import ConfigHandler
+from .validator import IntValidator
+from .utils import deep_compare, parse_bool, parse_int, patch_config
 
 logger = logging.getLogger(__name__)
 
@@ -30,9 +35,129 @@ _AUTH_ALLOWED_PARAMETERS = (
 )
 
 
-def default_validator(conf):
+def default_validator(conf: Dict[str, Any]) -> List[str]:
     if not conf:
         raise ConfigParseError("Config is empty.")
+    return []
+
+
+class GlobalConfig(object):
+
+    """A class that wrapps global configuration and provides convinient methods to access/check values.
+
+    It is instantiated by calling :func:`Config.global_config` method which picks either a
+    configuration from provided :class:`Cluster` object (the most up-to-date) or from the
+    local cache if :class::`ClusterConfig` is not initialized or doesn't have a valid config.
+    """
+
+    def __init__(self, config: Dict[str, Any]) -> None:
+        """Initialize :class:`GlobalConfig` object.
+
+        :param config: current configuration either from
+                       :class:`ClusterConfig` or from :class:`Config.dynamic_configuration`
+        """
+        self.__config = config
+
+    def get(self, name: str) -> Any:
+        """Gets global configuration value by name.
+
+        :param name: parameter name
+        :returns: configuration value or `None` if it is missing
+        """
+        return self.__config.get(name)
+
+    def check_mode(self, mode: str) -> bool:
+        """Checks whether the certain parameter is enabled.
+
+        :param mode: parameter name could be: synchronous_mode, failsafe_mode, pause, check_timeline, and so on
+        :returns: `True` if *mode* is enabled in the global configuration.
+        """
+        return bool(parse_bool(self.__config.get(mode)))
+
+    @property
+    def is_paused(self) -> bool:
+        """:returns: `True` if cluster is in maintenance mode."""
+        return self.check_mode('pause')
+
+    @property
+    def is_synchronous_mode(self) -> bool:
+        """:returns: `True` if synchronous replication is requested."""
+        return self.check_mode('synchronous_mode')
+
+    @property
+    def is_synchronous_mode_strict(self) -> bool:
+        """:returns: `True` if at least one synchronous node is required."""
+        return self.check_mode('synchronous_mode_strict')
+
+    def get_standby_cluster_config(self) -> Union[Dict[str, Any], Any]:
+        """:returns: "standby_cluster" configuration."""
+        return deepcopy(self.get('standby_cluster'))
+
+    @property
+    def is_standby_cluster(self) -> bool:
+        """:returns: `True` if global configuration has a valid "standby_cluster" section."""
+        config = self.get_standby_cluster_config()
+        return isinstance(config, dict) and\
+            bool(config.get('host') or config.get('port') or config.get('restore_command'))
+
+    def get_int(self, name: str, default: int = 0) -> int:
+        """Gets current value from the global configuration and trying to return it as int.
+
+        :param name: name of the parameter
+        :param default: default value if *name* is not in the configuration or invalid
+        :returns: currently configured value from the global configuration or *default* if it is not set or invalid.
+        """
+        ret = parse_int(self.get(name))
+        return default if ret is None else ret
+
+    @property
+    def min_synchronous_nodes(self) -> int:
+        """:returns: the minimal number of synchronous nodes based on whether strict mode is requested or not."""
+        return 1 if self.is_synchronous_mode_strict else 0
+
+    @property
+    def synchronous_node_count(self) -> int:
+        """:returns: currently configured value from the global configuration or 1 if it is not set or invalid."""
+        return max(self.get_int('synchronous_node_count', 1), self.min_synchronous_nodes)
+
+    @property
+    def maximum_lag_on_failover(self) -> int:
+        """:returns: currently configured value from the global configuration or 1048576 if it is not set or invalid."""
+        return self.get_int('maximum_lag_on_failover', 1048576)
+
+    @property
+    def maximum_lag_on_syncnode(self) -> int:
+        """:returns: currently configured value from the global configuration or -1 if it is not set or invalid."""
+        return self.get_int('maximum_lag_on_syncnode', -1)
+
+    @property
+    def primary_start_timeout(self) -> int:
+        """:returns: currently configured value from the global configuration or 300 if it is not set or invalid."""
+        default = 300
+        return self.get_int('primary_start_timeout', default)\
+            if 'primary_start_timeout' in self.__config else self.get_int('master_start_timeout', default)
+
+    @property
+    def primary_stop_timeout(self) -> int:
+        """:returns: currently configured value from the global configuration or 300 if it is not set or invalid."""
+        default = 0
+        return self.get_int('primary_stop_timeout', default)\
+            if 'primary_stop_timeout' in self.__config else self.get_int('master_stop_timeout', default)
+
+
+def get_global_config(cluster: Union[Cluster, None], default: Optional[Dict[str, Any]] = None) -> GlobalConfig:
+    """Instantiates :class:`GlobalConfig` based on the input.
+
+    :param cluster: the currently known cluster state from DCS
+    :param default: default configuration, which will be used if there is no valid *cluster.config*
+    :returns: :class:`GlobalConfig` object
+    """
+    # Try to protect from the case when DCS was wiped out
+    if cluster and cluster.config and cluster.config.modify_version:
+        config = cluster.config.data
+    else:
+        config = default or {}
+    return GlobalConfig(deepcopy(config))
 
 
 class Config(object):
@@ -58,21 +183,8 @@ class Config(object):
     PATRONI_CONFIG_VARIABLE = PATRONI_ENV_PREFIX + 'CONFIGURATION'
 
     __CACHE_FILENAME = 'patroni.dynamic.json'
-    __REMAP_KEYS = {
-        'master_start_timeout': 'primary_start_timeout',
-        'master_stop_timeout': 'primary_stop_timeout'
-    }
-    __DEFAULT_CONFIG = {
+    __DEFAULT_CONFIG: Dict[str, Any] = {
         'ttl': 30, 'loop_wait': 10, 'retry_timeout': 10,
-        'maximum_lag_on_failover': 1048576,
-        'maximum_lag_on_syncnode': -1,
-        'check_timeline': False,
-        'primary_start_timeout': 300,
-        'primary_stop_timeout': 0,
-        'synchronous_mode': False,
-        'synchronous_mode_strict': False,
-        'synchronous_node_count': 1,
-        'failsafe_mode': False,
         'standby_cluster': {
             'create_replica_methods': '',
             'host': '',
@@ -87,25 +199,24 @@ class Config(object):
             'use_slots': True,
             'parameters': CaseInsensitiveDict({p: v[0] for p, v in ConfigHandler.CMDLINE_OPTIONS.items()
                                                if p not in ('wal_keep_segments', 'wal_keep_size')})
-        },
-        'watchdog': {
-            'mode': 'automatic',
         }
     }
 
-    def __init__(self, configfile, validator=default_validator):
-        self._modify_index = -1
+    def __init__(self, configfile: str,
+                 validator: Optional[Callable[[Dict[str, Any]], List[str]]] = default_validator) -> None:
+        self._modify_version = -1
         self._dynamic_configuration = {}
 
         self.__environment_configuration = self._build_environment_configuration()
 
         # Patroni reads the configuration from the command-line argument if it exists, otherwise from the environment
-        self._config_file = configfile and os.path.exists(configfile) and configfile
+        self._config_file = configfile if configfile and os.path.exists(configfile) else None
         if self._config_file:
             self._local_configuration = self._load_config_file()
         else:
             config_env = os.environ.pop(self.PATRONI_CONFIG_VARIABLE, None)
             self._local_configuration = config_env and yaml.safe_load(config_env) or self.__environment_configuration
+
         if validator:
             errors = validator(self._local_configuration)
             if errors:
@@ -114,21 +225,19 @@ class Config(object):
         self.__effective_configuration = self._build_effective_configuration({}, self._local_configuration)
         self._data_dir = self.__effective_configuration.get('postgresql', {}).get('data_dir', "")
         self._cache_file = os.path.join(self._data_dir, self.__CACHE_FILENAME)
-        self._load_cache()
+        if validator:  # patronictl uses validator=None and we don't want to load anything from local cache in this case
+            self._load_cache()
         self._cache_needs_saving = False
 
     @property
-    def config_file(self):
+    def config_file(self) -> Union[str, None]:
         return self._config_file
 
     @property
-    def dynamic_configuration(self):
+    def dynamic_configuration(self) -> Dict[str, Any]:
         return deepcopy(self._dynamic_configuration)
 
-    def check_mode(self, mode):
-        return bool(parse_bool(self._dynamic_configuration.get(mode)))
-
-    def _load_config_path(self, path):
+    def _load_config_path(self, path: str) -> Dict[str, Any]:
         """
         If path is a file, loads the yml file pointed to by path.
         If path is a directory, loads all yml files in that directory in alphabetical order
@@ -142,20 +251,22 @@ class Config(object):
             logger.error('config path %s is neither directory nor file', path)
             raise ConfigParseError('invalid config path')
 
-        overall_config = {}
+        overall_config: Dict[str, Any] = {}
         for fname in files:
             with open(fname) as f:
                 config = yaml.safe_load(f)
                 patch_config(overall_config, config)
         return overall_config
 
-    def _load_config_file(self):
+    def _load_config_file(self) -> Dict[str, Any]:
         """Loads config.yaml from filesystem and applies some values which were set via ENV"""
+        if TYPE_CHECKING:  # pragma: no cover
+            assert self._config_file is not None
         config = self._load_config_path(self._config_file)
         patch_config(config, self.__environment_configuration)
         return config
 
-    def _load_cache(self):
+    def _load_cache(self) -> None:
         if os.path.isfile(self._cache_file):
             try:
                 with open(self._cache_file) as f:
@@ -163,15 +274,17 @@ class Config(object):
             except Exception:
                 logger.exception('Exception when loading file: %s', self._cache_file)
 
-    def save_cache(self):
+    def save_cache(self) -> None:
         if self._cache_needs_saving:
             tmpfile = fd = None
             try:
+                pg_perm.set_permissions_from_data_directory(self._data_dir)
                 (fd, tmpfile) = tempfile.mkstemp(prefix=self.__CACHE_FILENAME, dir=self._data_dir)
                 with os.fdopen(fd, 'w') as f:
                     fd = None
                     json.dump(self.dynamic_configuration, f)
                 tmpfile = shutil.move(tmpfile, self._cache_file)
+                os.chmod(self._cache_file, pg_perm.file_create_mode)
                 self._cache_needs_saving = False
             except Exception:
                 logger.exception('Exception when saving file: %s', self._cache_file)
@@ -187,11 +300,11 @@ class Config(object):
                         logger.error('Can not remove temporary file %s', tmpfile)
 
     # configuration could be either ClusterConfig or dict
-    def set_dynamic_configuration(self, configuration):
+    def set_dynamic_configuration(self, configuration: Union[ClusterConfig, Dict[str, Any]]) -> bool:
         if isinstance(configuration, ClusterConfig):
-            if self._modify_index == configuration.modify_index:
-                return False  # If the index didn't changed there is nothing to do
-            self._modify_index = configuration.modify_index
+            if self._modify_version == configuration.modify_version:
+                return False  # If the version didn't changed there is nothing to do
+            self._modify_version = configuration.modify_version
             configuration = configuration.data
 
         if not deep_compare(self._dynamic_configuration, configuration):
@@ -203,8 +316,9 @@ class Config(object):
                 return True
             except Exception:
                 logger.exception('Exception when setting dynamic_configuration')
+        return False
 
-    def reload_local_configuration(self):
+    def reload_local_configuration(self) -> Optional[bool]:
         if self.config_file:
             try:
                 configuration = self._load_config_file()
@@ -219,18 +333,27 @@ class Config(object):
                 logger.exception('Exception when reloading local configuration from %s', self.config_file)
 
     @staticmethod
-    def _process_postgresql_parameters(parameters, is_local=False):
-        return {name: value for name, value in (parameters or {}).items()
-                if name not in ConfigHandler.CMDLINE_OPTIONS or
-                not is_local and ConfigHandler.CMDLINE_OPTIONS[name][1](value)}
+    def _process_postgresql_parameters(parameters: Dict[str, Any], is_local: bool = False) -> Dict[str, Any]:
+        pg_params: Dict[str, Any] = {}
 
-    def _safe_copy_dynamic_configuration(self, dynamic_configuration):
+        for name, value in (parameters or {}).items():
+            if name not in ConfigHandler.CMDLINE_OPTIONS:
+                pg_params[name] = value
+            elif not is_local:
+                validator = ConfigHandler.CMDLINE_OPTIONS[name][1]
+                if validator(value):
+                    int_val = parse_int(value) if isinstance(validator, IntValidator) else None
+                    pg_params[name] = int_val if isinstance(int_val, int) else value
+                else:
+                    logger.warning("postgresql parameter %s=%s failed validation, defaulting to %s",
+                                   name, value, ConfigHandler.CMDLINE_OPTIONS[name][0])
+
+        return pg_params
+
+    def _safe_copy_dynamic_configuration(self, dynamic_configuration: Dict[str, Any]) -> Dict[str, Any]:
         config = deepcopy(self.__DEFAULT_CONFIG)
 
         for name, value in dynamic_configuration.items():
-            # allow copying master_start_timeout->primary_start_timeout when the latter isn't in dynamic_configuration
-            if name in self.__REMAP_KEYS and self.__REMAP_KEYS[name] not in dynamic_configuration:
-                name = self.__REMAP_KEYS[name]
             if name == 'postgresql':
                 for name, value in (value or {}).items():
                     if name == 'parameters':
@@ -243,17 +366,14 @@ class Config(object):
                     if name in self.__DEFAULT_CONFIG['standby_cluster']:
                         config['standby_cluster'][name] = deepcopy(value)
             elif name in config:  # only variables present in __DEFAULT_CONFIG allowed to be overridden from DCS
-                if name in ('synchronous_mode', 'synchronous_mode_strict', 'failsafe_mode'):
-                    config[name] = value
-                else:
-                    config[name] = int(value)
+                config[name] = int(value)
         return config
 
     @staticmethod
-    def _build_environment_configuration():
-        ret = defaultdict(dict)
+    def _build_environment_configuration() -> Dict[str, Any]:
+        ret: Dict[str, Any] = defaultdict(dict)
 
-        def _popenv(name):
+        def _popenv(name: str) -> Union[str, None]:
             return os.environ.pop(PATRONI_ENV_PREFIX + name.upper(), None)
 
         for param in ('name', 'namespace', 'scope'):
@@ -261,7 +381,7 @@ class Config(object):
             if value:
                 ret[param] = value
 
-        def _fix_log_env(name, oldname):
+        def _fix_log_env(name: str, oldname: str) -> None:
             value = _popenv(oldname)
             name = PATRONI_ENV_PREFIX + 'LOG_' + name.upper()
             if value and name not in os.environ:
@@ -270,7 +390,7 @@ class Config(object):
         for name, oldname in (('level', 'loglevel'), ('format', 'logformat'), ('dateformat', 'log_datefmt')):
             _fix_log_env(name, oldname)
 
-        def _set_section_values(section, params):
+        def _set_section_values(section: str, params: List[str]) -> None:
             for param in params:
                 value = _popenv(section + '_' + param)
                 if value:
@@ -278,7 +398,8 @@ class Config(object):
 
         _set_section_values('restapi', ['listen', 'connect_address', 'certfile', 'keyfile', 'keyfile_password',
                                         'cafile', 'ciphers', 'verify_client', 'http_extra_headers',
-                                        'https_extra_headers', 'allowlist', 'allowlist_include_members'])
+                                        'https_extra_headers', 'allowlist', 'allowlist_include_members',
+                                        'request_queue_size'])
         _set_section_values('ctl', ['insecure', 'cacert', 'certfile', 'keyfile', 'keyfile_password'])
         _set_section_values('postgresql', ['listen', 'connect_address', 'proxy_address',
                                            'config_dir', 'data_dir', 'pgpass', 'bin_dir'])
@@ -286,6 +407,11 @@ class Config(object):
                                     'dir', 'file_size', 'file_num', 'loggers'])
         _set_section_values('raft', ['data_dir', 'self_addr', 'partner_addrs', 'password', 'bind_addr'])
 
+        for binary in ('pg_ctl', 'initdb', 'pg_controldata', 'pg_basebackup', 'postgres', 'pg_isready', 'pg_rewind'):
+            value = _popenv('POSTGRESQL_BIN_' + binary)
+            if value:
+                ret['postgresql'].setdefault('bin_name', {})[binary] = value
+
         for first, second in (('restapi', 'allowlist_include_members'), ('ctl', 'insecure')):
             value = ret.get(first, {}).pop(second, None)
             if value:
@@ -293,14 +419,16 @@ class Config(object):
                 if value is not None:
                     ret[first][second] = value
 
-        for second in ('max_queue_size', 'file_size', 'file_num'):
-            value = ret.get('log', {}).pop(second, None)
-            if value:
-                value = parse_int(value)
-                if value is not None:
-                    ret['log'][second] = value
+        for first, params in (('restapi', ('request_queue_size',)),
+                              ('log', ('max_queue_size', 'file_size', 'file_num'))):
+            for second in params:
+                value = ret.get(first, {}).pop(second, None)
+                if value:
+                    value = parse_int(value)
+                    if value is not None:
+                        ret[first][second] = value
 
-        def _parse_list(value):
+        def _parse_list(value: str) -> Union[List[str], None]:
             if not (value.strip().startswith('-') or '[' in value):
                 value = '[{0}]'.format(value)
             try:
@@ -316,7 +444,7 @@ class Config(object):
                 if value:
                     ret[first][second] = value
 
-        def _parse_dict(value):
+        def _parse_dict(value: str) -> Union[Dict[str, Any], None]:
             if not value.strip().startswith('{'):
                 value = '{{{0}}}'.format(value)
             try:
@@ -333,17 +461,18 @@ class Config(object):
                     if value:
                         ret[first][second] = value
 
-        def _get_auth(name, params=None):
-            ret = {}
+        def _get_auth(name: str, params: Optional[Collection[str]] = None) -> Dict[str, str]:
+            ret: Dict[str, str] = {}
             for param in params or _AUTH_ALLOWED_PARAMETERS[:2]:
                 value = _popenv(name + '_' + param)
                 if value:
                     ret[param] = value
             return ret
 
-        restapi_auth = _get_auth('restapi')
-        if restapi_auth:
-            ret['restapi']['authentication'] = restapi_auth
+        for section in ('ctl', 'restapi'):
+            auth = _get_auth(section)
+            if auth:
+                ret[section]['authentication'] = auth
 
         authentication = {}
         for user_type in ('replication', 'superuser', 'rewind'):
@@ -363,7 +492,8 @@ class Config(object):
                               'REGISTER_SERVICE', 'SERVICE_CHECK_INTERVAL', 'SERVICE_CHECK_TLS_SERVER_NAME',
                               'SERVICE_TAGS', 'NAMESPACE', 'CONTEXT', 'USE_ENDPOINTS', 'SCOPE_LABEL', 'ROLE_LABEL',
                               'POD_IP', 'PORTS', 'LABELS', 'BYPASS_API_SERVICE', 'RETRIABLE_HTTP_CODES', 'KEY_PASSWORD',
-                              'USE_SSL', 'SET_ACLS', 'GROUP', 'DATABASE') and name:
+                              'USE_SSL', 'SET_ACLS', 'GROUP', 'DATABASE', 'LEADER_LABEL_VALUE', 'FOLLOWER_LABEL_VALUE',
+                              'STANDBY_LEADER_LABEL_VALUE', 'TMP_ROLE_LABEL') and name:
                     value = os.environ.pop(param)
                     if name == 'CITUS':
                         if suffix == 'GROUP':
@@ -403,7 +533,8 @@ class Config(object):
 
         return ret
 
-    def _build_effective_configuration(self, dynamic_configuration, local_configuration):
+    def _build_effective_configuration(self, dynamic_configuration: Dict[str, Any],
+                                       local_configuration: Dict[str, Union[Dict[str, Any], Any]]) -> Dict[str, Any]:
         config = self._safe_copy_dynamic_configuration(dynamic_configuration)
         for name, value in local_configuration.items():
             if name == 'citus':  # remove invalid citus configuration
@@ -419,9 +550,10 @@ class Config(object):
             elif name not in config or name in ['watchdog']:
                 config[name] = deepcopy(value) if value else {}
 
-        # restapi server expects to get restapi.auth = 'username:password'
-        if 'restapi' in config and 'authentication' in config['restapi']:
-            config['restapi']['auth'] = '{username}:{password}'.format(**config['restapi']['authentication'])
+        # restapi server expects to get restapi.auth = 'username:password' and similarly for `ctl`
+        for section in ('ctl', 'restapi'):
+            if section in config and 'authentication' in config[section]:
+                config[section]['auth'] = '{username}:{password}'.format(**config[section]['authentication'])
 
         # special treatment for old config
 
@@ -458,10 +590,6 @@ class Config(object):
             'name',
             'scope',
             'retry_timeout',
-            'synchronous_mode',
-            'synchronous_mode_strict',
-            'synchronous_node_count',
-            'maximum_lag_on_syncnode',
             'citus'
         )
 
@@ -469,14 +597,24 @@ class Config(object):
 
         return config
 
-    def get(self, key, default=None):
+    def get(self, key: str, default: Optional[Any] = None) -> Any:
         return self.__effective_configuration.get(key, default)
 
-    def __contains__(self, key):
+    def __contains__(self, key: str) -> bool:
         return key in self.__effective_configuration
 
-    def __getitem__(self, key):
+    def __getitem__(self, key: str) -> Any:
         return self.__effective_configuration[key]
 
-    def copy(self):
+    def copy(self) -> Dict[str, Any]:
         return deepcopy(self.__effective_configuration)
+
+    def get_global_config(self, cluster: Union[Cluster, None]) -> GlobalConfig:
+        """Instantiate :class:`GlobalConfig` based on input.
+
+        Use the configuration from provided *cluster* (the most up-to-date) or from the
+        local cache if *cluster.config* is not initialized or doesn't have a valid config.
+        :param cluster: the currently known cluster state from DCS
+        :returns: :class:`GlobalConfig` object
+        """
+        return get_global_config(cluster, self._dynamic_configuration)

patroni/daemon.py

@@ -6,15 +6,32 @@ Currently it is only used for the main "Thread" of ``patroni`` and ``patroni_raf
 from __future__ import print_function
 
 import abc
+import argparse
 import os
 import signal
 import sys
 
 from threading import Lock
-from typing import Any, Optional, Type
+from typing import Any, Optional, Type, TYPE_CHECKING
 
-from .config import Config
-from .validator import Schema
+if TYPE_CHECKING:  # pragma: no cover
+    from .config import Config
+
+
+def get_base_arg_parser() -> argparse.ArgumentParser:
+    """Create a basic argument parser with the arguments used for both patroni and raft controller daemon.
+
+    :returns: 'argparse.ArgumentParser' object
+    """
+    from .config import Config
+    from .version import __version__
+
+    parser = argparse.ArgumentParser()
+    parser.add_argument('--version', action='version', version='%(prog)s {0}'.format(__version__))
+    parser.add_argument('configfile', nargs='?', default='',
+                        help='Patroni may also read the configuration from the {0} environment variable'
+                        .format(Config.PATRONI_CONFIG_VARIABLE))
+    return parser
 
 
 class AbstractPatroniDaemon(abc.ABC):
@@ -30,7 +47,7 @@ class AbstractPatroniDaemon(abc.ABC):
     :ivar config: configuration options for this daemon.
     """
 
-    def __init__(self, config: Config) -> None:
+    def __init__(self, config: 'Config') -> None:
         """Set up signal handlers, logging handler and configuration.
 
         :param config: configuration options for this daemon.
@@ -94,7 +111,7 @@ class AbstractPatroniDaemon(abc.ABC):
         with self._sigterm_lock:
             return self._received_sigterm
 
-    def reload_config(self, sighup: Optional[bool] = False, local: Optional[bool] = False) -> None:
+    def reload_config(self, sighup: bool = False, local: Optional[bool] = False) -> None:
         """Reload configuration.
 
         :param sighup: if it is related to a SIGHUP signal.
@@ -140,41 +157,17 @@ class AbstractPatroniDaemon(abc.ABC):
         self.logger.shutdown()
 
 
-def abstract_main(cls: Type[AbstractPatroniDaemon], validator: Optional[Schema] = None) -> None:
+def abstract_main(cls: Type[AbstractPatroniDaemon], configfile: str) -> None:
     """Create the main entry point of a given daemon process.
 
-    Expose a basic argument parser, parse the command-line arguments, and run the given daemon process.
-
     :param cls: a class that should inherit from :class:`AbstractPatroniDaemon`.
-    :param validator: used to validate the daemon configuration schema, if requested by the user through
-        ``--validate-config`` CLI option.
+    :param configfile:
     """
-    import argparse
-
     from .config import Config, ConfigParseError
-    from .version import __version__
-
-    parser = argparse.ArgumentParser()
-    parser.add_argument('--version', action='version', version='%(prog)s {0}'.format(__version__))
-    if validator:
-        parser.add_argument('--validate-config', action='store_true', help='Run config validator and exit')
-    parser.add_argument('configfile', nargs='?', default='',
-                        help='Patroni may also read the configuration from the {0} environment variable'
-                        .format(Config.PATRONI_CONFIG_VARIABLE))
-    args = parser.parse_args()
-    validate_config = validator and args.validate_config
     try:
-        if validate_config:
-            Config(args.configfile, validator=validator)
-            sys.exit()
-
-        config = Config(args.configfile)
+        config = Config(configfile)
     except ConfigParseError as e:
-        if e.value:
-            print(e.value, file=sys.stderr)
-        if not validate_config:
-            parser.print_help()
-        sys.exit(1)
+        sys.exit(e.value)
 
     controller = cls(config)
     try:

patroni/dcs/consul.py

@@ -8,16 +8,19 @@ import ssl
 import time
 import urllib3
 
-from collections import defaultdict, namedtuple
+from collections import defaultdict
 from consul import ConsulException, NotFound, base
 from http.client import HTTPException
 from urllib3.exceptions import HTTPError
 from urllib.parse import urlencode, urlparse, quote
+from typing import Any, Callable, Dict, List, Mapping, NamedTuple, Optional, Union, Tuple, TYPE_CHECKING
 
-from . import AbstractDCS, Cluster, ClusterConfig, Failover, Leader, Member, SyncState,\
-        TimelineHistory, ReturnFalseException, catch_return_false_exception, citus_group_re
+from . import AbstractDCS, Cluster, ClusterConfig, Failover, Leader, Member, SyncState, \
+    TimelineHistory, ReturnFalseException, catch_return_false_exception, citus_group_re
 from ..exceptions import DCSError
 from ..utils import deep_compare, parse_bool, Retry, RetryFailedError, split_host_port, uri, USER_AGENT
+if TYPE_CHECKING:  # pragma: no cover
+    from ..config import Config
 
 logger = logging.getLogger(__name__)
 
@@ -38,12 +41,17 @@ class InvalidSession(ConsulException):
     """invalid session"""
 
 
-Response = namedtuple('Response', 'code,headers,body,content')
+class Response(NamedTuple):
+    code: int
+    headers: Union[Mapping[str, str], Mapping[bytes, bytes], None]
+    body: str
+    content: bytes
 
 
 class HTTPClient(object):
 
-    def __init__(self, host='127.0.0.1', port=8500, token=None, scheme='http', verify=True, cert=None, ca_cert=None):
+    def __init__(self, host: str = '127.0.0.1', port: int = 8500, token: Optional[str] = None, scheme: str = 'http',
+                 verify: bool = True, cert: Optional[str] = None, ca_cert: Optional[str] = None) -> None:
         self.token = token
         self._read_timeout = 10
         self.base_uri = uri(scheme, (host, port))
@@ -59,23 +67,23 @@ class HTTPClient(object):
         if ca_cert:
             kwargs['ca_certs'] = ca_cert
         kwargs['cert_reqs'] = ssl.CERT_REQUIRED if verify or ca_cert else ssl.CERT_NONE
-        self.http = urllib3.PoolManager(num_pools=10, maxsize=10, **kwargs)
-        self._ttl = None
+        self.http = urllib3.PoolManager(num_pools=10, maxsize=10, headers={}, **kwargs)
+        self._ttl = 30
 
-    def set_read_timeout(self, timeout):
-        self._read_timeout = timeout/3.0
+    def set_read_timeout(self, timeout: float) -> None:
+        self._read_timeout = timeout / 3.0
 
     @property
-    def ttl(self):
+    def ttl(self) -> int:
         return self._ttl
 
-    def set_ttl(self, ttl):
+    def set_ttl(self, ttl: int) -> bool:
         ret = self._ttl != ttl
         self._ttl = ttl
         return ret
 
     @staticmethod
-    def response(response):
+    def response(response: urllib3.response.HTTPResponse) -> Response:
         content = response.data
         body = content.decode('utf-8')
         if response.status == 500:
@@ -88,14 +96,19 @@ class HTTPClient(object):
                 raise ConsulInternalError(msg)
         return Response(response.status, response.headers, body, content)
 
-    def uri(self, path, params=None):
+    def uri(self, path: str,
+            params: Union[None, Dict[str, Any], List[Tuple[str, Any]], Tuple[Tuple[str, Any], ...]] = None) -> str:
         return '{0}{1}{2}'.format(self.base_uri, path, params and '?' + urlencode(params) or '')
 
-    def __getattr__(self, method):
+    def __getattr__(self, method: str) -> Callable[[Callable[[Response], Union[bool, Any, Tuple[str, Any]]],
+                                                    str, Union[None, Dict[str, Any], List[Tuple[str, Any]]],
+                                                    str, Optional[Dict[str, str]]], Union[bool, Any, Tuple[str, Any]]]:
         if method not in ('get', 'post', 'put', 'delete'):
             raise AttributeError("HTTPClient instance has no attribute '{0}'".format(method))
 
-        def wrapper(callback, path, params=None, data='', headers=None):
+        def wrapper(callback: Callable[[Response], Union[bool, Any, Tuple[str, Any]]], path: str,
+                    params: Union[None, Dict[str, Any], List[Tuple[str, Any]]] = None, data: str = '',
+                    headers: Optional[Dict[str, str]] = None) -> Union[bool, Any, Tuple[str, Any]]:
             # python-consul doesn't allow to specify ttl smaller then 10 seconds
             # because session_ttl_min defaults to 10s, so we have to do this ugly dirty hack...
             if method == 'put' and path == '/v1/session/create':
@@ -106,14 +119,14 @@ class HTTPClient(object):
                     data = data[:-1] + ', ' + ttl + '}'
             if isinstance(params, list):  # starting from v1.1.0 python-consul switched from `dict` to `list` for params
                 params = {k: v for k, v in params}
-            kwargs = {'retries': 0, 'preload_content': False, 'body': data}
+            kwargs: Dict[str, Any] = {'retries': 0, 'preload_content': False, 'body': data}
             if method == 'get' and isinstance(params, dict) and 'index' in params:
                 timeout = float(params['wait'][:-1]) if 'wait' in params else 300
                 # According to the documentation a small random amount of additional wait time is added to the
                 # supplied maximum wait time to spread out the wake up time of any concurrent requests. This adds
                 # up to wait / 16 additional time to the maximum duration. Since our goal is actually getting a
                 # response rather read timeout we will add to the timeout a slightly bigger value.
-                kwargs['timeout'] = timeout + max(timeout/15.0, 1)
+                kwargs['timeout'] = timeout + max(timeout / 15.0, 1)
             else:
                 kwargs['timeout'] = self._read_timeout
             kwargs['headers'] = (headers or {}).copy()
@@ -127,13 +140,13 @@ class HTTPClient(object):
 
 class ConsulClient(base.Consul):
 
-    def __init__(self, *args, **kwargs):
+    def __init__(self, *args: Any, **kwargs: Any) -> None:
         self._cert = kwargs.pop('cert', None)
         self._ca_cert = kwargs.pop('ca_cert', None)
         self.token = kwargs.get('token')
         super(ConsulClient, self).__init__(*args, **kwargs)
 
-    def http_connect(self, *args, **kwargs):
+    def http_connect(self, *args: Any, **kwargs: Any) -> HTTPClient:
         kwargs.update(dict(zip(['host', 'port', 'scheme', 'verify'], args)))
         if self._cert:
             kwargs['cert'] = self._cert
@@ -143,17 +156,17 @@ class ConsulClient(base.Consul):
             kwargs['token'] = self.token
         return HTTPClient(**kwargs)
 
-    def connect(self, *args, **kwargs):
+    def connect(self, *args: Any, **kwargs: Any) -> HTTPClient:
         return self.http_connect(*args, **kwargs)
 
-    def reload_config(self, config):
+    def reload_config(self, config: Dict[str, Any]) -> None:
         self.http.token = self.token = config.get('token')
         self.consistency = config.get('consistency', 'default')
         self.dc = config.get('dc')
 
 
-def catch_consul_errors(func):
-    def wrapper(*args, **kwargs):
+def catch_consul_errors(func: Callable[..., Any]) -> Callable[..., Any]:
+    def wrapper(*args: Any, **kwargs: Any) -> Any:
         try:
             return func(*args, **kwargs)
         except (RetryFailedError, ConsulException, HTTPException, HTTPError, socket.error, socket.timeout):
@@ -161,24 +174,25 @@ def catch_consul_errors(func):
     return wrapper
 
 
-def force_if_last_failed(func):
-    def wrapper(*args, **kwargs):
-        if wrapper.last_result is False:
+def force_if_last_failed(func: Callable[..., Any]) -> Callable[..., Any]:
+    def wrapper(*args: Any, **kwargs: Any) -> Any:
+        if getattr(wrapper, 'last_result', None) is False:
             kwargs['force'] = True
-        wrapper.last_result = func(*args, **kwargs)
-        return wrapper.last_result
+        last_result = func(*args, **kwargs)
+        setattr(wrapper, 'last_result', last_result)
+        return last_result
 
-    wrapper.last_result = None
+    setattr(wrapper, 'last_result', None)
     return wrapper
 
 
-def service_name_from_scope_name(scope_name):
+def service_name_from_scope_name(scope_name: str) -> str:
     """Translate scope name to service name which can be used in dns.
 
     230 = 253 - len('replica.') - len('.service.consul')
     """
 
-    def replace_char(match):
+    def replace_char(match: Any) -> str:
         c = match.group(0)
         return '-' if c in '. _' else "u{:04d}".format(ord(c))
 
@@ -188,7 +202,7 @@ def service_name_from_scope_name(scope_name):
 
 class Consul(AbstractDCS):
 
-    def __init__(self, config):
+    def __init__(self, config: Dict[str, Any]) -> None:
         super(Consul, self).__init__(config)
         self._base_path = self._base_path[1:]
         self._scope = config['scope']
@@ -198,9 +212,9 @@ class Consul(AbstractDCS):
                             retry_exceptions=(ConsulInternalError, HTTPException,
                                               HTTPError, socket.error, socket.timeout))
 
-        kwargs = {}
         if 'url' in config:
-            r = urlparse(config['url'])
+            url: str = config['url']
+            r = urlparse(url)
             config.update({'scheme': r.scheme, 'host': r.hostname, 'port': r.port or 8500})
         elif 'host' in config:
             host, port = split_host_port(config.get('host', '127.0.0.1:8500'), 8500)
@@ -215,7 +229,7 @@ class Consul(AbstractDCS):
             config['cert'] = (config['cert'], config['key'])
 
         config_keys = ('host', 'port', 'token', 'scheme', 'cert', 'ca_cert', 'dc', 'consistency')
-        kwargs = {p: config.get(p) for p in config_keys if config.get(p)}
+        kwargs: Dict[str, Any] = {p: config.get(p) for p in config_keys if config.get(p)}
 
         verify = config.get('verify')
         if not isinstance(verify, bool):
@@ -240,10 +254,10 @@ class Consul(AbstractDCS):
             self.create_session()
         self._previous_loop_token = self._client.token
 
-    def retry(self, *args, **kwargs):
-        return self._retry.copy()(*args, **kwargs)
+    def retry(self, method: Callable[..., Any], *args: Any, **kwargs: Any) -> Any:
+        return self._retry.copy()(method, *args, **kwargs)
 
-    def create_session(self):
+    def create_session(self) -> None:
         while not self._session:
             try:
                 self.refresh_session()
@@ -251,13 +265,14 @@ class Consul(AbstractDCS):
                 logger.info('waiting on consul')
                 time.sleep(5)
 
-    def reload_config(self, config):
+    def reload_config(self, config: Union['Config', Dict[str, Any]]) -> None:
         super(Consul, self).reload_config(config)
 
         consul_config = config.get('consul', {})
         self._client.reload_config(consul_config)
         self._previous_loop_service_tags = self._service_tags
-        self._service_tags = sorted(consul_config.get('service_tags', []))
+        self._service_tags: List[str] = consul_config.get('service_tags', [])
+        self._service_tags.sort()
 
         should_register_service = consul_config.get('register_service', False)
         if should_register_service and not self._register_service:
@@ -266,29 +281,30 @@ class Consul(AbstractDCS):
         self._previous_loop_register_service = self._register_service
         self._register_service = should_register_service
 
-    def set_ttl(self, ttl):
-        if self._client.http.set_ttl(ttl/2.0):  # Consul multiplies the TTL by 2x
+    def set_ttl(self, ttl: int) -> Optional[bool]:
+        if self._client.http.set_ttl(ttl / 2.0):  # Consul multiplies the TTL by 2x
             self._session = None
             self.__do_not_watch = True
+        return None
 
     @property
-    def ttl(self):
+    def ttl(self) -> int:
         return self._client.http.ttl * 2  # we multiply the value by 2 because it was divided in the `set_ttl()` method
 
-    def set_retry_timeout(self, retry_timeout):
+    def set_retry_timeout(self, retry_timeout: int) -> None:
         self._retry.deadline = retry_timeout
         self._client.http.set_read_timeout(retry_timeout)
 
-    def adjust_ttl(self):
+    def adjust_ttl(self) -> None:
         try:
             settings = self._client.agent.self()
-            min_ttl = (settings['Config']['SessionTTLMin'] or 10000000000)/1000000000.0
+            min_ttl = (settings['Config']['SessionTTLMin'] or 10000000000) / 1000000000.0
             logger.warning('Changing Session TTL from %s to %s', self._client.http.ttl, min_ttl)
             self._client.http.set_ttl(min_ttl)
         except Exception:
             logger.exception('adjust_ttl')
 
-    def _do_refresh_session(self, force=False):
+    def _do_refresh_session(self, force: bool = False) -> bool:
         """:returns: `!True` if it had to create new session"""
         if not force and self._session and self._last_session_refresh + self._loop_wait > time.time():
             return False
@@ -312,7 +328,7 @@ class Consul(AbstractDCS):
         self._last_session_refresh = time.time()
         return ret
 
-    def refresh_session(self):
+    def refresh_session(self) -> bool:
         try:
             return self.retry(self._do_refresh_session)
         except (ConsulException, RetryFailedError):
@@ -320,10 +336,10 @@ class Consul(AbstractDCS):
         raise ConsulError('Failed to renew/create session')
 
     @staticmethod
-    def member(node):
+    def member(node: Dict[str, str]) -> Member:
         return Member.from_node(node['ModifyIndex'], os.path.basename(node['Key']), node.get('Session'), node['Value'])
 
-    def _cluster_from_nodes(self, nodes):
+    def _cluster_from_nodes(self, nodes: Dict[str, Any]) -> Cluster:
         # get initialize flag
         initialize = nodes.get(self._INITIALIZE)
         initialize = initialize and initialize['Value']
@@ -351,7 +367,7 @@ class Consul(AbstractDCS):
             slots = None
 
         try:
-            last_lsn = int(last_lsn)
+            last_lsn = int(last_lsn or '')
         except Exception:
             last_lsn = 0
 
@@ -384,8 +400,12 @@ class Consul(AbstractDCS):
 
         return Cluster(initialize, config, leader, last_lsn, members, failover, sync, history, slots, failsafe)
 
-    def _cluster_loader(self, path):
-        _, results = self.retry(self._client.kv.get, path, recurse=True)
+    @property
+    def _consistency(self) -> str:
+        return 'consistent' if self._ctl else self._client.consistency
+
+    def _cluster_loader(self, path: str) -> Cluster:
+        _, results = self.retry(self._client.kv.get, path, recurse=True, consistency=self._consistency)
         if results is None:
             raise NotFound
         nodes = {}
@@ -395,9 +415,9 @@ class Consul(AbstractDCS):
 
         return self._cluster_from_nodes(nodes)
 
-    def _citus_cluster_loader(self, path):
-        _, results = self.retry(self._client.kv.get, path, recurse=True)
-        clusters = defaultdict(dict)
+    def _citus_cluster_loader(self, path: str) -> Dict[int, Cluster]:
+        _, results = self.retry(self._client.kv.get, path, recurse=True, consistency=self._consistency)
+        clusters: Dict[int, Dict[str, Cluster]] = defaultdict(dict)
         for node in results or []:
             key = node['Key'][len(path):].split('/', 1)
             if len(key) == 2 and citus_group_re.match(key[0]):
@@ -405,7 +425,9 @@ class Consul(AbstractDCS):
                 clusters[int(key[0])][key[1]] = node
         return {group: self._cluster_from_nodes(nodes) for group, nodes in clusters.items()}
 
-    def _load_cluster(self, path, loader):
+    def _load_cluster(
+            self, path: str, loader: Callable[[str], Union[Cluster, Dict[int, Cluster]]]
+    ) -> Union[Cluster, Dict[int, Cluster]]:
         try:
             return loader(path)
         except NotFound:
@@ -415,7 +437,7 @@ class Consul(AbstractDCS):
             raise ConsulError('Consul is not responding properly')
 
     @catch_consul_errors
-    def touch_member(self, data):
+    def touch_member(self, data: Dict[str, Any]) -> bool:
         cluster = self.cluster
         member = cluster and cluster.get_member(self._name, fallback_to_leader=False)
 
@@ -447,30 +469,32 @@ class Consul(AbstractDCS):
             logger.exception('touch_member')
         return False
 
-    def _set_service_name(self):
+    def _set_service_name(self) -> None:
         self._service_name = service_name_from_scope_name(self._scope)
         if self._scope != self._service_name:
             logger.warning('Using %s as consul service name instead of scope name %s', self._service_name, self._scope)
 
     @catch_consul_errors
-    def register_service(self, service_name, **kwargs):
+    def register_service(self, service_name: str, **kwargs: Any) -> bool:
         logger.info('Register service %s, params %s', service_name, kwargs)
         return self._client.agent.service.register(service_name, **kwargs)
 
     @catch_consul_errors
-    def deregister_service(self, service_id):
+    def deregister_service(self, service_id: str) -> bool:
         logger.info('Deregister service %s', service_id)
         # service_id can contain special characters, but is used as part of uri in deregister request
         service_id = quote(service_id)
         return self._client.agent.service.deregister(service_id)
 
-    def _update_service(self, data):
+    def _update_service(self, data: Dict[str, Any]) -> Optional[bool]:
         service_name = self._service_name
         role = data['role'].replace('_', '-')
         state = data['state']
-        api_parts = urlparse(data['api_url'])
+        api_url: str = data['api_url']
+        api_parts = urlparse(api_url)
         api_parts = api_parts._replace(path='/{0}'.format(role))
-        conn_parts = urlparse(data['conn_url'])
+        conn_url: str = data['conn_url']
+        conn_parts = urlparse(conn_url)
         check = base.Check.http(api_parts.geturl(), self._service_check_interval,
                                 deregister='{0}s'.format(self._client.http.ttl * 10))
         if self._service_check_tls_server_name is not None:
@@ -506,7 +530,7 @@ class Consul(AbstractDCS):
         logger.warning('Could not register service: unknown role type %s', role)
 
     @force_if_last_failed
-    def update_service(self, old_data, new_data, force=False):
+    def update_service(self, old_data: Dict[str, Any], new_data: Dict[str, Any], force: bool = False) -> Optional[bool]:
         update = False
 
         for key in ['role', 'api_url', 'conn_url', 'state']:
@@ -523,30 +547,26 @@ class Consul(AbstractDCS):
         ):
             return self._update_service(new_data)
 
-    def _do_attempt_to_acquire_leader(self, retry):
+    def _do_attempt_to_acquire_leader(self, retry: Retry) -> bool:
         try:
             return retry(self._client.kv.put, self.leader_path, self._name, acquire=self._session)
         except InvalidSession:
             logger.error('Our session disappeared from Consul. Will try to get a new one and retry attempt')
             self._session = None
-            retry.deadline = retry.stoptime - time.time()
+            retry.ensure_deadline(0)
 
             retry(self._do_refresh_session)
 
-            retry.deadline = retry.stoptime - time.time()
-            if retry.deadline < 1:
-                raise ConsulError('_do_attempt_to_acquire_leader timeout')
+            retry.ensure_deadline(1, ConsulError('_do_attempt_to_acquire_leader timeout'))
 
             return retry(self._client.kv.put, self.leader_path, self._name, acquire=self._session)
 
     @catch_return_false_exception
-    def attempt_to_acquire_leader(self):
+    def attempt_to_acquire_leader(self) -> bool:
         retry = self._retry.copy()
         self._run_and_handle_exceptions(self._do_refresh_session, retry=retry)
 
-        retry.deadline = retry.stoptime - time.time()
-        if retry.deadline < 1:
-            raise ConsulError('attempt_to_acquire_leader timeout')
+        retry.ensure_deadline(1, ConsulError('attempt_to_acquire_leader timeout'))
 
         ret = self._run_and_handle_exceptions(self._do_attempt_to_acquire_leader, retry, retry=None)
         if not ret:
@@ -554,31 +574,31 @@ class Consul(AbstractDCS):
 
         return ret
 
-    def take_leader(self):
+    def take_leader(self) -> bool:
         return self.attempt_to_acquire_leader()
 
     @catch_consul_errors
-    def set_failover_value(self, value, index=None):
-        return self._client.kv.put(self.failover_path, value, cas=index)
+    def set_failover_value(self, value: str, version: Optional[int] = None) -> bool:
+        return self._client.kv.put(self.failover_path, value, cas=version)
 
     @catch_consul_errors
-    def set_config_value(self, value, index=None):
-        return self._client.kv.put(self.config_path, value, cas=index)
+    def set_config_value(self, value: str, version: Optional[int] = None) -> bool:
+        return self._client.kv.put(self.config_path, value, cas=version)
 
     @catch_consul_errors
-    def _write_leader_optime(self, last_lsn):
+    def _write_leader_optime(self, last_lsn: str) -> bool:
         return self._client.kv.put(self.leader_optime_path, last_lsn)
 
     @catch_consul_errors
-    def _write_status(self, value):
+    def _write_status(self, value: str) -> bool:
         return self._client.kv.put(self.status_path, value)
 
     @catch_consul_errors
-    def _write_failsafe(self, value):
+    def _write_failsafe(self, value: str) -> bool:
         return self._client.kv.put(self.failsafe_path, value)
 
     @staticmethod
-    def _run_and_handle_exceptions(method, *args, **kwargs):
+    def _run_and_handle_exceptions(method: Callable[..., Any], *args: Any, **kwargs: Any) -> Any:
         retry = kwargs.pop('retry', None)
         try:
             return retry(method, *args, **kwargs) if retry else method(*args, **kwargs)
@@ -588,73 +608,76 @@ class Consul(AbstractDCS):
             raise ReturnFalseException
 
     @catch_return_false_exception
-    def _update_leader(self):
+    def _update_leader(self, leader: Leader) -> bool:
         retry = self._retry.copy()
 
         self._run_and_handle_exceptions(self._do_refresh_session, True, retry=retry)
 
-        if self._session:
-            cluster = self.cluster
-            leader_session = cluster and isinstance(cluster.leader, Leader) and cluster.leader.session
-            if leader_session != self._session:
-                retry.deadline = retry.stoptime - time.time()
-                if retry.deadline < 1:
-                    raise ConsulError('update_leader timeout')
-                logger.warning('Recreating the leader key due to session mismatch')
-                if cluster.leader:
-                    self._run_and_handle_exceptions(self._client.kv.delete, self.leader_path, cas=cluster.leader.index)
+        if self._session and leader.session != self._session:
+            retry.ensure_deadline(1, ConsulError('update_leader timeout'))
 
-                retry.deadline = retry.stoptime - time.time()
-                if retry.deadline < 0.5:
-                    raise ConsulError('update_leader timeout')
-                self._run_and_handle_exceptions(self._client.kv.put, self.leader_path,
-                                                self._name, acquire=self._session)
+            logger.warning('Recreating the leader key due to session mismatch')
+            self._run_and_handle_exceptions(self._client.kv.delete, self.leader_path, cas=leader.version)
+
+            retry.ensure_deadline(0.5, ConsulError('update_leader timeout'))
+
+            self._run_and_handle_exceptions(self._client.kv.put, self.leader_path, self._name, acquire=self._session)
 
         return bool(self._session)
 
     @catch_consul_errors
-    def initialize(self, create_new=True, sysid=''):
+    def initialize(self, create_new: bool = True, sysid: str = '') -> bool:
         kwargs = {'cas': 0} if create_new else {}
         return self.retry(self._client.kv.put, self.initialize_path, sysid, **kwargs)
 
     @catch_consul_errors
-    def cancel_initialization(self):
+    def cancel_initialization(self) -> bool:
         return self.retry(self._client.kv.delete, self.initialize_path)
 
     @catch_consul_errors
-    def delete_cluster(self):
+    def delete_cluster(self) -> bool:
         return self.retry(self._client.kv.delete, self.client_path(''), recurse=True)
 
     @catch_consul_errors
-    def set_history_value(self, value):
+    def set_history_value(self, value: str) -> bool:
         return self._client.kv.put(self.history_path, value)
 
     @catch_consul_errors
-    def _delete_leader(self):
+    def _delete_leader(self) -> bool:
         cluster = self.cluster
-        if cluster and isinstance(cluster.leader, Leader) and cluster.leader.name == self._name:
-            return self._client.kv.delete(self.leader_path, cas=cluster.leader.index)
+        if cluster and isinstance(cluster.leader, Leader) and\
+                cluster.leader.name == self._name and isinstance(cluster.leader.version, int):
+            return self._client.kv.delete(self.leader_path, cas=cluster.leader.version)
+        return True
 
     @catch_consul_errors
-    def set_sync_state_value(self, value, index=None):
-        return self.retry(self._client.kv.put, self.sync_path, value, cas=index)
+    def set_sync_state_value(self, value: str, version: Optional[int] = None) -> Union[int, bool]:
+        retry = self._retry.copy()
+        ret = retry(self._client.kv.put, self.sync_path, value, cas=version)
+        if ret:  # We have no other choise, only read after write :(
+            if not retry.ensure_deadline(0.5):
+                return False
+            _, ret = self.retry(self._client.kv.get, self.sync_path)
+            if ret and (ret.get('Value') or b'').decode('utf-8') == value:
+                return ret['ModifyIndex']
+        return False
 
     @catch_consul_errors
-    def delete_sync_state(self, index=None):
-        return self.retry(self._client.kv.delete, self.sync_path, cas=index)
+    def delete_sync_state(self, version: Optional[int] = None) -> bool:
+        return self.retry(self._client.kv.delete, self.sync_path, cas=version)
 
-    def watch(self, leader_index, timeout):
+    def watch(self, leader_version: Optional[int], timeout: float) -> bool:
         self._last_session_refresh = 0
         if self.__do_not_watch:
             self.__do_not_watch = False
             return True
 
-        if leader_index:
+        if leader_version:
             end_time = time.time() + timeout
             while timeout >= 1:
                 try:
-                    idx, _ = self._client.kv.get(self.leader_path, index=leader_index, wait=str(timeout) + 's')
-                    return str(idx) != str(leader_index)
+                    idx, _ = self._client.kv.get(self.leader_path, index=leader_version, wait=str(timeout) + 's')
+                    return str(idx) != str(leader_version)
                 except (ConsulException, HTTPException, HTTPError, socket.error, socket.timeout):
                     logger.exception('watch')
 

patroni/dcs/etcd.py

@@ -16,16 +16,18 @@ from dns import resolver
 from http.client import HTTPException
 from queue import Queue
 from threading import Thread
-from typing import List, Optional
+from typing import Any, Callable, Collection, Dict, List, Optional, Union, Tuple, Type, TYPE_CHECKING
 from urllib.parse import urlparse
 from urllib3 import Timeout
 from urllib3.exceptions import HTTPError, ReadTimeoutError, ProtocolError
 
-from . import AbstractDCS, Cluster, ClusterConfig, Failover, Leader, Member, SyncState,\
-        TimelineHistory, ReturnFalseException, catch_return_false_exception, citus_group_re
+from . import AbstractDCS, Cluster, ClusterConfig, Failover, Leader, Member, SyncState, \
+    TimelineHistory, ReturnFalseException, catch_return_false_exception, citus_group_re
 from ..exceptions import DCSError
 from ..request import get as requests_get
 from ..utils import Retry, RetryFailedError, split_host_port, uri, USER_AGENT
+if TYPE_CHECKING:  # pragma: no cover
+    from ..config import Config
 
 logger = logging.getLogger(__name__)
 
@@ -38,18 +40,21 @@ class EtcdError(DCSError):
     pass
 
 
+_AddrInfo = Tuple[socket.AddressFamily, socket.SocketKind, int, str, Union[Tuple[str, int], Tuple[str, int, int, int]]]
+
+
 class DnsCachingResolver(Thread):
 
-    def __init__(self, cache_time=600.0, cache_fail_time=30.0):
+    def __init__(self, cache_time: float = 600.0, cache_fail_time: float = 30.0) -> None:
         super(DnsCachingResolver, self).__init__()
-        self._cache = {}
+        self._cache: Dict[Tuple[str, int], Tuple[float, List[_AddrInfo]]] = {}
         self._cache_time = cache_time
         self._cache_fail_time = cache_fail_time
-        self._resolve_queue = Queue()
+        self._resolve_queue: Queue[Tuple[Tuple[str, int], int]] = Queue()
         self.daemon = True
         self.start()
 
-    def run(self):
+    def run(self) -> None:
         while True:
             (host, port), attempt = self._resolve_queue.get()
             response = self._do_resolve(host, port)
@@ -60,7 +65,7 @@ class DnsCachingResolver(Thread):
                     self.resolve_async(host, port, attempt + 1)
                     time.sleep(1)
 
-    def resolve(self, host, port):
+    def resolve(self, host: str, port: int) -> List[_AddrInfo]:
         current_time = time.time()
         cached_time, response = self._cache.get((host, port), (0, []))
         time_passed = current_time - cached_time
@@ -71,14 +76,14 @@ class DnsCachingResolver(Thread):
                 response = new_response
         return response
 
-    def resolve_async(self, host, port, attempt=0):
+    def resolve_async(self, host: str, port: int, attempt: int = 0) -> None:
         self._resolve_queue.put(((host, port), attempt))
 
-    def remove(self, host, port):
+    def remove(self, host: str, port: int) -> None:
         self._cache.pop((host, port), None)
 
     @staticmethod
-    def _do_resolve(host, port):
+    def _do_resolve(host: str, port: int) -> List[_AddrInfo]:
         try:
             return socket.getaddrinfo(host, port, 0, socket.SOCK_STREAM, socket.IPPROTO_TCP)
         except Exception as e:
@@ -88,13 +93,15 @@ class DnsCachingResolver(Thread):
 
 class AbstractEtcdClientWithFailover(abc.ABC, etcd.Client):
 
-    def __init__(self, config, dns_resolver, cache_ttl=300):
+    ERROR_CLS: Type[Exception]
+
+    def __init__(self, config: Dict[str, Any], dns_resolver: DnsCachingResolver, cache_ttl: int = 300) -> None:
         self._dns_resolver = dns_resolver
         self.set_machines_cache_ttl(cache_ttl)
         self._machines_cache_updated = 0
-        args = {p: config.get(p) for p in ('host', 'port', 'protocol', 'use_proxies', 'username', 'password',
-                                           'cert', 'ca_cert') if config.get(p)}
-        super(AbstractEtcdClientWithFailover, self).__init__(read_timeout=config['retry_timeout'], **args)
+        kwargs = {p: config.get(p) for p in ('host', 'port', 'protocol', 'use_proxies', 'version_prefix',
+                                             'username', 'password', 'cert', 'ca_cert') if config.get(p)}
+        super(AbstractEtcdClientWithFailover, self).__init__(read_timeout=config['retry_timeout'], **kwargs)
         # For some reason python3-etcd on debian and ubuntu are not based on the latest version
         # Workaround for the case when https://github.com/jplana/python-etcd/pull/196 is not applied
         self.http.connection_pool_kw.pop('ssl_version', None)
@@ -106,7 +113,7 @@ class AbstractEtcdClientWithFailover(abc.ABC, etcd.Client):
         self._read_options.add('retry')
         self._del_conditions.add('retry')
 
-    def _calculate_timeouts(self, etcd_nodes, timeout=None):
+    def _calculate_timeouts(self, etcd_nodes: int, timeout: Optional[float] = None) -> Tuple[int, float, int]:
         """Calculate a request timeout and number of retries per single etcd node.
         In case if the timeout per node is too small (less than one second) we will reduce the number of nodes.
         For the cluster with only one node we will try to do 2 retries.
@@ -133,38 +140,39 @@ class AbstractEtcdClientWithFailover(abc.ABC, etcd.Client):
 
         return etcd_nodes, per_node_timeout, per_node_retries - 1
 
-    def reload_config(self, config):
+    def reload_config(self, config: Dict[str, Any]) -> None:
         self.username = config.get('username')
         self.password = config.get('password')
 
-    def _get_headers(self):
+    def _get_headers(self) -> Dict[str, str]:
         basic_auth = ':'.join((self.username, self.password)) if self.username and self.password else None
         return urllib3.make_headers(basic_auth=basic_auth, user_agent=USER_AGENT)
 
-    def _prepare_common_parameters(self, etcd_nodes, timeout=None):
-        kwargs = {'headers': self._get_headers(), 'redirect': self.allow_redirect, 'preload_content': False}
+    def _prepare_common_parameters(self, etcd_nodes: int, timeout: Optional[float] = None) -> Dict[str, Any]:
+        kwargs: Dict[str, Any] = {'headers': self._get_headers(),
+                                  'redirect': self.allow_redirect, 'preload_content': False}
 
         if timeout is not None:
             kwargs.update(retries=0, timeout=timeout)
         else:
             _, per_node_timeout, per_node_retries = self._calculate_timeouts(etcd_nodes)
-            connect_timeout = max(1, per_node_timeout/2)
+            connect_timeout = max(1.0, per_node_timeout / 2.0)
             kwargs.update(timeout=Timeout(connect=connect_timeout, total=per_node_timeout), retries=per_node_retries)
         return kwargs
 
-    def set_machines_cache_ttl(self, cache_ttl):
+    def set_machines_cache_ttl(self, cache_ttl: int) -> None:
         self._machines_cache_ttl = cache_ttl
 
     @abc.abstractmethod
-    def _prepare_get_members(self, etcd_nodes):
+    def _prepare_get_members(self, etcd_nodes: int) -> Dict[str, Any]:
         """returns: request parameters"""
 
     @abc.abstractmethod
-    def _get_members(self, base_uri, **kwargs):
+    def _get_members(self, base_uri: str, **kwargs: Any) -> List[str]:
         """returns: list of clientURLs"""
 
     @property
-    def machines_cache(self):
+    def machines_cache(self) -> List[str]:
         base_uri, cache = self._base_uri, self._machines_cache
         return ([base_uri] if base_uri in cache else []) + [machine for machine in cache if machine != base_uri]
 
@@ -207,10 +215,14 @@ class AbstractEtcdClientWithFailover(abc.ABC, etcd.Client):
 
         return self._get_machines_list(self.machines_cache)
 
-    def set_read_timeout(self, timeout):
+    def set_read_timeout(self, timeout: float) -> None:
         self._read_timeout = timeout
 
-    def _do_http_request(self, retry, machines_cache, request_executor, method, path, fields=None, **kwargs):
+    def _do_http_request(self, retry: Optional[Retry], machines_cache: List[str],
+                         request_executor: Callable[..., urllib3.response.HTTPResponse],
+                         method: str, path: str, fields: Optional[Dict[str, Any]] = None,
+                         **kwargs: Any) -> urllib3.response.HTTPResponse:
+        is_watch_request = isinstance(fields, dict) and fields.get('wait') == 'true'
         if fields is not None:
             kwargs['fields'] = fields
         some_request_failed = False
@@ -233,8 +245,7 @@ class AbstractEtcdClientWithFailover(abc.ABC, etcd.Client):
                     # whether the key didn't received an update or there is a network problem.
                     elif i + 1 < len(machines_cache):
                         self.set_base_uri(machines_cache[i + 1])
-                if (isinstance(fields, dict) and fields.get("wait") == "true" and
-                        isinstance(e, (ReadTimeoutError, ProtocolError))):
+                if is_watch_request and isinstance(e, (ReadTimeoutError, ProtocolError)):
                     logger.debug("Watch timed out.")
                     raise etcd.EtcdWatchTimedOut("Watch timed out: {0}".format(e), cause=e)
                 logger.error("Request to server %s failed: %r", base_uri, e)
@@ -246,10 +257,12 @@ class AbstractEtcdClientWithFailover(abc.ABC, etcd.Client):
         raise etcd.EtcdConnectionFailed('No more machines in the cluster')
 
     @abc.abstractmethod
-    def _prepare_request(self, kwargs, params=None, method=None):
+    def _prepare_request(self, kwargs: Dict[str, Any], params: Optional[Dict[str, Any]] = None,
+                         method: Optional[str] = None) -> Callable[..., urllib3.response.HTTPResponse]:
         """returns: request_executor"""
 
-    def api_execute(self, path, method, params=None, timeout=None):
+    def api_execute(self, path: str, method: str, params: Optional[Dict[str, Any]] = None,
+                    timeout: Optional[float] = None) -> Any:
         retry = params.pop('retry', None) if isinstance(params, dict) else None
 
         # Update machines_cache if previous attempt of update has failed
@@ -277,6 +290,8 @@ class AbstractEtcdClientWithFailover(abc.ABC, etcd.Client):
                         etcd_nodes = len(machines_cache)
                 except Exception as e:
                     logger.debug('Failed to update list of etcd nodes: %r', e)
+                if TYPE_CHECKING:  # pragma: no cover
+                    assert isinstance(retry, Retry)  # etcd.EtcdConnectionFailed is raised only if retry is not None!
                 sleeptime = retry.sleeptime
                 remaining_time = retry.stoptime - sleeptime - time.time()
                 nodes, timeout, retries = self._calculate_timeouts(etcd_nodes, remaining_time)
@@ -287,22 +302,22 @@ class AbstractEtcdClientWithFailover(abc.ABC, etcd.Client):
                 retry.sleep_func(sleeptime)
                 retry.update_delay()
                 # We still have some time left. Partially reduce `machines_cache` and retry request
-                kwargs.update(timeout=Timeout(connect=max(1, timeout/2), total=timeout), retries=retries)
+                kwargs.update(timeout=Timeout(connect=max(1.0, timeout / 2.0), total=timeout), retries=retries)
                 machines_cache = machines_cache[:nodes]
 
     @staticmethod
-    def get_srv_record(host):
+    def get_srv_record(host: str) -> List[Tuple[str, int]]:
         try:
             return [(r.target.to_text(True), r.port) for r in resolver.query(host, 'SRV')]
         except DNSException:
             return []
 
-    def _get_machines_cache_from_srv(self, srv, srv_suffix=None):
+    def _get_machines_cache_from_srv(self, srv: str, srv_suffix: Optional[str] = None) -> List[str]:
         """Fetch list of etcd-cluster member by resolving _etcd-server._tcp. SRV record.
         This record should contain list of host and peer ports which could be used to run
         'GET http://{host}:{port}/members' request (peer protocol)"""
 
-        ret = []
+        ret: List[str] = []
         for r in ['-client-ssl', '-client', '-ssl', '', '-server-ssl', '-server']:
             r = '{0}-{1}'.format(r, srv_suffix) if srv_suffix else r
             protocol = 'https' if '-ssl' in r else 'http'
@@ -327,15 +342,15 @@ class AbstractEtcdClientWithFailover(abc.ABC, etcd.Client):
             logger.warning('Can not resolve SRV for %s', srv)
         return list(set(ret))
 
-    def _get_machines_cache_from_dns(self, host, port):
+    def _get_machines_cache_from_dns(self, host: str, port: int) -> List[str]:
         """One host might be resolved into multiple ip addresses. We will make list out of it"""
         if self.protocol == 'http':
-            ret = map(lambda res: uri(self.protocol, res[-1][:2]), self._dns_resolver.resolve(host, port))
+            ret = [uri(self.protocol, res[-1][:2]) for res in self._dns_resolver.resolve(host, port)]
             if ret:
                 return list(set(ret))
         return [uri(self.protocol, (host, port))]
 
-    def _get_machines_cache_from_config(self):
+    def _get_machines_cache_from_config(self) -> List[str]:
         if 'proxy' in self._config:
             return [uri(self.protocol, (self._config['host'], self._config['port']))]
 
@@ -351,13 +366,14 @@ class AbstractEtcdClientWithFailover(abc.ABC, etcd.Client):
         return machines_cache
 
     @staticmethod
-    def _update_dns_cache(func, machines):
+    def _update_dns_cache(func: Callable[[str, int], None], machines: List[str]) -> None:
         for url in machines:
             r = urlparse(url)
-            port = r.port or (443 if r.scheme == 'https' else 80)
-            func(r.hostname, port)
+            if r.hostname:
+                port = r.port or (443 if r.scheme == 'https' else 80)
+                func(r.hostname, port)
 
-    def _load_machines_cache(self):
+    def _load_machines_cache(self) -> bool:
         """This method should fill up `_machines_cache` from scratch.
         It could happen only in two cases:
         1. During class initialization
@@ -417,7 +433,7 @@ class AbstractEtcdClientWithFailover(abc.ABC, etcd.Client):
         self._machines_cache_updated = time.time()
         return ret
 
-    def set_base_uri(self, value):
+    def set_base_uri(self, value: str) -> None:
         if self._base_uri != value:
             logger.info('Selected new etcd server %s', value)
             self._base_uri = value
@@ -427,22 +443,25 @@ class EtcdClient(AbstractEtcdClientWithFailover):
 
     ERROR_CLS = EtcdError
 
-    def __del__(self):
-        if self.http is not None:
-            try:
-                self.http.clear()
-            except (ReferenceError, TypeError, AttributeError):
-                pass
+    def __init__(self, config: Dict[str, Any], dns_resolver: DnsCachingResolver, cache_ttl: int = 300) -> None:
+        super(EtcdClient, self).__init__({**config, 'version_prefix': None}, dns_resolver, cache_ttl)
 
-    def _prepare_get_members(self, etcd_nodes):
+    def __del__(self) -> None:
+        try:
+            self.http.clear()
+        except (ReferenceError, TypeError, AttributeError):
+            pass
+
+    def _prepare_get_members(self, etcd_nodes: int) -> Dict[str, Any]:
         return self._prepare_common_parameters(etcd_nodes)
 
-    def _get_members(self, base_uri, **kwargs):
+    def _get_members(self, base_uri: str, **kwargs: Any) -> List[str]:
         response = self.http.request(self._MGET, base_uri + self.version_prefix + '/machines', **kwargs)
         data = self._handle_server_response(response).data.decode('utf-8')
         return [m.strip() for m in data.split(',') if m.strip()]
 
-    def _prepare_request(self, kwargs, params=None, method=None):
+    def _prepare_request(self, kwargs: Dict[str, Any], params: Optional[Dict[str, Any]] = None,
+                         method: Optional[str] = None) -> Callable[..., urllib3.response.HTTPResponse]:
         kwargs['fields'] = params
         if method in (self._MPOST, self._MPUT):
             kwargs['encode_multipart'] = False
@@ -451,25 +470,32 @@ class EtcdClient(AbstractEtcdClientWithFailover):
 
 class AbstractEtcd(AbstractDCS):
 
-    def __init__(self, config, client_cls, retry_errors_cls):
+    def __init__(self, config: Dict[str, Any], client_cls: Type[AbstractEtcdClientWithFailover],
+                 retry_errors_cls: Union[Type[Exception], Tuple[Type[Exception], ...]]) -> None:
         super(AbstractEtcd, self).__init__(config)
         self._retry = Retry(deadline=config['retry_timeout'], max_delay=1, max_tries=-1,
                             retry_exceptions=retry_errors_cls)
         self._ttl = int(config.get('ttl') or 30)
-        self._client = self.get_etcd_client(config, client_cls)
+        self._abstract_client = self.get_etcd_client(config, client_cls)
         self.__do_not_watch = False
         self._has_failed = False
 
-    def reload_config(self, config):
+    @property
+    @abc.abstractmethod
+    def _client(self) -> AbstractEtcdClientWithFailover:
+        """return correct type of etcd client"""
+
+    def reload_config(self, config: Union['Config', Dict[str, Any]]) -> None:
         super(AbstractEtcd, self).reload_config(config)
         self._client.reload_config(config.get(self.__class__.__name__.lower(), {}))
 
-    def retry(self, *args, **kwargs):
+    def retry(self, method: Callable[..., Any], *args: Any, **kwargs: Any) -> Any:
         retry = self._retry.copy()
         kwargs['retry'] = retry
-        return retry(*args, **kwargs)
+        return retry(method, *args, **kwargs)
 
-    def _handle_exception(self, e, name='', do_sleep=False, raise_ex=None):
+    def _handle_exception(self, e: Exception, name: str = '', do_sleep: bool = False,
+                          raise_ex: Optional[Exception] = None) -> None:
         if not self._has_failed:
             logger.exception(name)
         else:
@@ -480,7 +506,18 @@ class AbstractEtcd(AbstractDCS):
         if isinstance(raise_ex, Exception):
             raise raise_ex
 
-    def _run_and_handle_exceptions(self, method, *args, **kwargs):
+    def handle_etcd_exceptions(self, func: Callable[..., Any], *args: Any, **kwargs: Any) -> Any:
+        try:
+            retval = func(self, *args, **kwargs)
+            self._has_failed = False
+            return retval
+        except (RetryFailedError, etcd.EtcdException) as e:
+            self._handle_exception(e)
+            return False
+        except Exception as e:
+            self._handle_exception(e, raise_ex=self._client.ERROR_CLS('unexpected error'))
+
+    def _run_and_handle_exceptions(self, method: Callable[..., Any], *args: Any, **kwargs: Any) -> Any:
         retry = kwargs.pop('retry', self.retry)
         try:
             return retry(method, *args, **kwargs) if retry else method(*args, **kwargs)
@@ -492,19 +529,20 @@ class AbstractEtcd(AbstractDCS):
         except Exception as e:
             self._handle_exception(e, raise_ex=self._client.ERROR_CLS('unexpected error'))
 
-    @staticmethod
-    def set_socket_options(sock, socket_options):
+    def set_socket_options(self, sock: socket.socket,
+                           socket_options: Optional[Collection[Tuple[int, int, int]]]) -> None:
         if socket_options:
             for opt in socket_options:
                 sock.setsockopt(*opt)
 
-    def get_etcd_client(self, config, client_cls):
+    def get_etcd_client(self, config: Dict[str, Any],
+                        client_cls: Type[AbstractEtcdClientWithFailover]) -> AbstractEtcdClientWithFailover:
         config = deepcopy(config)
         if 'proxy' in config:
             config['use_proxies'] = True
             config['url'] = config['proxy']
 
-        if 'url' in config:
+        if 'url' in config and isinstance(config['url'], str):
             r = urlparse(config['url'])
             config.update({'protocol': r.scheme, 'host': r.hostname, 'port': r.port or 2379,
                            'username': r.username, 'password': r.password})
@@ -516,10 +554,11 @@ class AbstractEtcd(AbstractDCS):
             if isinstance(hosts, str):
                 hosts = hosts.split(',')
 
-            config['hosts'] = []
+            config_hosts: List[str] = []
             for value in hosts:
                 if isinstance(value, str):
-                    config['hosts'].append(uri(protocol, split_host_port(value.strip(), default_port)))
+                    config_hosts.append(uri(protocol, split_host_port(value.strip(), default_port)))
+            config['hosts'] = config_hosts
         elif 'host' in config:
             host, port = split_host_port(config['host'], 2379)
             config['host'] = host
@@ -538,8 +577,10 @@ class AbstractEtcd(AbstractDCS):
 
         dns_resolver = DnsCachingResolver()
 
-        def create_connection_patched(address, timeout=socket._GLOBAL_DEFAULT_TIMEOUT,
-                                      source_address=None, socket_options=None):
+        def create_connection_patched(
+                address: Tuple[str, int], timeout: Any = object(),
+                source_address: Optional[Any] = None, socket_options: Optional[Collection[Tuple[int, int, int]]] = None
+        ) -> socket.socket:
             host, port = address
             if host.startswith('['):
                 host = host.strip('[]')
@@ -549,7 +590,7 @@ class AbstractEtcd(AbstractDCS):
                 try:
                     sock = socket.socket(af, socktype, proto)
                     self.set_socket_options(sock, socket_options)
-                    if timeout is not socket._GLOBAL_DEFAULT_TIMEOUT:
+                    if timeout is None or isinstance(timeout, (float, int)):
                         sock.settimeout(timeout)
                     if source_address:
                         sock.bind(source_address)
@@ -580,51 +621,49 @@ class AbstractEtcd(AbstractDCS):
                 time.sleep(5)
         return client
 
-    def set_ttl(self, ttl):
+    def set_ttl(self, ttl: int) -> Optional[bool]:
         ttl = int(ttl)
         ret = self._ttl != ttl
         self._ttl = ttl
-        self._client.set_machines_cache_ttl(ttl*10)
+        self._client.set_machines_cache_ttl(ttl * 10)
         return ret
 
     @property
-    def ttl(self):
+    def ttl(self) -> int:
         return self._ttl
 
-    def set_retry_timeout(self, retry_timeout):
+    def set_retry_timeout(self, retry_timeout: int) -> None:
         self._retry.deadline = retry_timeout
         self._client.set_read_timeout(retry_timeout)
 
 
-def catch_etcd_errors(func):
-    def wrapper(self, *args, **kwargs):
-        try:
-            retval = func(self, *args, **kwargs) is not None
-            self._has_failed = False
-            return retval
-        except (RetryFailedError, etcd.EtcdException) as e:
-            self._handle_exception(e)
-            return False
-        except Exception as e:
-            self._handle_exception(e, raise_ex=self._client.ERROR_CLS('unexpected error'))
-
+def catch_etcd_errors(func: Callable[..., Any]) -> Any:
+    def wrapper(self: AbstractEtcd, *args: Any, **kwargs: Any) -> Any:
+        return self.handle_etcd_exceptions(func, *args, **kwargs)
     return wrapper
 
 
 class Etcd(AbstractEtcd):
 
-    def __init__(self, config):
+    def __init__(self, config: Dict[str, Any]) -> None:
         super(Etcd, self).__init__(config, EtcdClient, (etcd.EtcdLeaderElectionInProgress, EtcdRaftInternal))
         self.__do_not_watch = False
 
-    def set_ttl(self, ttl):
+    @property
+    def _client(self) -> EtcdClient:
+        if TYPE_CHECKING:  # pragma: no cover
+            assert isinstance(self._abstract_client, EtcdClient)
+        return self._abstract_client
+
+    def set_ttl(self, ttl: int) -> Optional[bool]:
         self.__do_not_watch = super(Etcd, self).set_ttl(ttl)
+        return None
 
     @staticmethod
-    def member(node):
+    def member(node: etcd.EtcdResult) -> Member:
         return Member.from_node(node.modifiedIndex, os.path.basename(node.key), node.ttl, node.value)
 
-    def _cluster_from_nodes(self, etcd_index, nodes):
+    def _cluster_from_nodes(self, etcd_index: int, nodes: Dict[str, etcd.EtcdResult]) -> Cluster:
         # get initialize flag
         initialize = nodes.get(self._INITIALIZE)
         initialize = initialize and initialize.value
@@ -652,7 +691,7 @@ class Etcd(AbstractEtcd):
             slots = None
 
         try:
-            last_lsn = int(last_lsn)
+            last_lsn = int(last_lsn or '')
         except Exception:
             last_lsn = 0
 
@@ -664,8 +703,8 @@ class Etcd(AbstractEtcd):
         if leader:
             member = Member(-1, leader.value, None, {})
             member = ([m for m in members if m.name == leader.value] or [member])[0]
-            index = etcd_index if etcd_index > leader.modifiedIndex else leader.modifiedIndex + 1
-            leader = Leader(index, leader.ttl, member)
+            version = etcd_index if etcd_index > leader.modifiedIndex else leader.modifiedIndex + 1
+            leader = Leader(version, leader.ttl, member)
 
         # failover key
         failover = nodes.get(self._FAILOVER)
@@ -685,21 +724,23 @@ class Etcd(AbstractEtcd):
 
         return Cluster(initialize, config, leader, last_lsn, members, failover, sync, history, slots, failsafe)
 
-    def _cluster_loader(self, path):
-        result = self.retry(self._client.read, path, recursive=True)
+    def _cluster_loader(self, path: str) -> Cluster:
+        result = self.retry(self._client.read, path, recursive=True, quorum=self._ctl)
         nodes = {node.key[len(result.key):].lstrip('/'): node for node in result.leaves}
         return self._cluster_from_nodes(result.etcd_index, nodes)
 
-    def _citus_cluster_loader(self, path):
-        clusters = defaultdict(dict)
-        result = self.retry(self._client.read, path, recursive=True)
+    def _citus_cluster_loader(self, path: str) -> Dict[int, Cluster]:
+        clusters: Dict[int, Dict[str, etcd.EtcdResult]] = defaultdict(dict)
+        result = self.retry(self._client.read, path, recursive=True, quorum=self._ctl)
         for node in result.leaves:
             key = node.key[len(result.key):].lstrip('/').split('/', 1)
             if len(key) == 2 and citus_group_re.match(key[0]):
                 clusters[int(key[0])][key[1]] = node
         return {group: self._cluster_from_nodes(result.etcd_index, nodes) for group, nodes in clusters.items()}
 
-    def _load_cluster(self, path, loader):
+    def _load_cluster(
+            self, path: str, loader: Callable[[str], Union[Cluster, Dict[int, Cluster]]]
+    ) -> Union[Cluster, Dict[int, Cluster]]:
         cluster = None
         try:
             cluster = loader(path)
@@ -708,18 +749,20 @@ class Etcd(AbstractEtcd):
         except Exception as e:
             self._handle_exception(e, 'get_cluster', raise_ex=EtcdError('Etcd is not responding properly'))
         self._has_failed = False
+        if TYPE_CHECKING:  # pragma: no cover
+            assert cluster is not None
         return cluster
 
     @catch_etcd_errors
-    def touch_member(self, data):
-        data = json.dumps(data, separators=(',', ':'))
-        return self._client.set(self.member_path, data, self._ttl)
+    def touch_member(self, data: Dict[str, Any]) -> bool:
+        value = json.dumps(data, separators=(',', ':'))
+        return bool(self._client.set(self.member_path, value, self._ttl))
 
     @catch_etcd_errors
-    def take_leader(self):
+    def take_leader(self) -> bool:
         return self.retry(self._client.write, self.leader_path, self._name, ttl=self._ttl)
 
-    def _do_attempt_to_acquire_leader(self):
+    def _do_attempt_to_acquire_leader(self) -> bool:
         try:
             return bool(self.retry(self._client.write, self.leader_path, self._name, ttl=self._ttl, prevExist=False))
         except etcd.EtcdAlreadyExist:
@@ -727,26 +770,26 @@ class Etcd(AbstractEtcd):
             return False
 
     @catch_return_false_exception
-    def attempt_to_acquire_leader(self):
+    def attempt_to_acquire_leader(self) -> bool:
         return self._run_and_handle_exceptions(self._do_attempt_to_acquire_leader, retry=None)
 
     @catch_etcd_errors
-    def set_failover_value(self, value, index=None):
-        return self._client.write(self.failover_path, value, prevIndex=index or 0)
+    def set_failover_value(self, value: str, version: Optional[int] = None) -> bool:
+        return bool(self._client.write(self.failover_path, value, prevIndex=version or 0))
 
     @catch_etcd_errors
-    def set_config_value(self, value, index=None):
-        return self._client.write(self.config_path, value, prevIndex=index or 0)
+    def set_config_value(self, value: str, version: Optional[int] = None) -> bool:
+        return bool(self._client.write(self.config_path, value, prevIndex=version or 0))
 
     @catch_etcd_errors
-    def _write_leader_optime(self, last_lsn):
-        return self._client.set(self.leader_optime_path, last_lsn)
+    def _write_leader_optime(self, last_lsn: str) -> bool:
+        return bool(self._client.set(self.leader_optime_path, last_lsn))
 
     @catch_etcd_errors
-    def _write_status(self, value):
-        return self._client.set(self.status_path, value)
+    def _write_status(self, value: str) -> bool:
+        return bool(self._client.set(self.status_path, value))
 
-    def _do_update_leader(self):
+    def _do_update_leader(self) -> bool:
         try:
             return self.retry(self._client.write, self.leader_path, self._name,
                               prevValue=self._name, ttl=self._ttl) is not None
@@ -754,52 +797,52 @@ class Etcd(AbstractEtcd):
             return self._do_attempt_to_acquire_leader()
 
     @catch_etcd_errors
-    def _write_failsafe(self, value):
-        return self._client.set(self.failsafe_path, value)
+    def _write_failsafe(self, value: str) -> bool:
+        return bool(self._client.set(self.failsafe_path, value))
 
     @catch_return_false_exception
-    def _update_leader(self):
-        return self._run_and_handle_exceptions(self._do_update_leader, retry=None)
+    def _update_leader(self, leader: Leader) -> bool:
+        return bool(self._run_and_handle_exceptions(self._do_update_leader, retry=None))
 
     @catch_etcd_errors
-    def initialize(self, create_new=True, sysid=""):
-        return self.retry(self._client.write, self.initialize_path, sysid, prevExist=(not create_new))
+    def initialize(self, create_new: bool = True, sysid: str = "") -> bool:
+        return bool(self.retry(self._client.write, self.initialize_path, sysid, prevExist=(not create_new)))
 
     @catch_etcd_errors
-    def _delete_leader(self):
-        return self._client.delete(self.leader_path, prevValue=self._name)
+    def _delete_leader(self) -> bool:
+        return bool(self._client.delete(self.leader_path, prevValue=self._name))
 
     @catch_etcd_errors
-    def cancel_initialization(self):
-        return self.retry(self._client.delete, self.initialize_path)
+    def cancel_initialization(self) -> bool:
+        return bool(self.retry(self._client.delete, self.initialize_path))
 
     @catch_etcd_errors
-    def delete_cluster(self):
-        return self.retry(self._client.delete, self.client_path(''), recursive=True)
+    def delete_cluster(self) -> bool:
+        return bool(self.retry(self._client.delete, self.client_path(''), recursive=True))
 
     @catch_etcd_errors
-    def set_history_value(self, value):
-        return self._client.write(self.history_path, value)
+    def set_history_value(self, value: str) -> bool:
+        return bool(self._client.write(self.history_path, value))
 
     @catch_etcd_errors
-    def set_sync_state_value(self, value, index=None):
-        return self.retry(self._client.write, self.sync_path, value, prevIndex=index or 0)
+    def set_sync_state_value(self, value: str, version: Optional[int] = None) -> Union[int, bool]:
+        return self.retry(self._client.write, self.sync_path, value, prevIndex=version or 0).modifiedIndex
 
     @catch_etcd_errors
-    def delete_sync_state(self, index=None):
-        return self.retry(self._client.delete, self.sync_path, prevIndex=index or 0)
+    def delete_sync_state(self, version: Optional[int] = None) -> bool:
+        return bool(self.retry(self._client.delete, self.sync_path, prevIndex=version or 0))
 
-    def watch(self, leader_index, timeout):
+    def watch(self, leader_version: Optional[int], timeout: float) -> bool:
         if self.__do_not_watch:
             self.__do_not_watch = False
             return True
 
-        if leader_index:
+        if leader_version:
             end_time = time.time() + timeout
 
             while timeout >= 1:  # when timeout is too small urllib3 doesn't have enough time to connect
                 try:
-                    result = self._client.watch(self.leader_path, index=leader_index, timeout=timeout + 0.5)
+                    result = self._client.watch(self.leader_path, index=leader_version, timeout=timeout + 0.5)
                     self._has_failed = False
                     if result.action == 'compareAndSwap':
                         time.sleep(0.01)

patroni/dcs/etcd3.py

@@ -10,12 +10,14 @@ import time
 import urllib3
 
 from collections import defaultdict
-from threading import Condition, Lock, Thread
+from enum import IntEnum
 from urllib3.exceptions import ReadTimeoutError, ProtocolError
+from threading import Condition, Lock, Thread
+from typing import Any, Callable, Collection, Dict, Iterator, List, Optional, Tuple, Type, TYPE_CHECKING, Union
 
-from . import ClusterConfig, Cluster, Failover, Leader, Member, SyncState,\
-        TimelineHistory, ReturnFalseException, catch_return_false_exception, citus_group_re
-from .etcd import AbstractEtcdClientWithFailover, AbstractEtcd, catch_etcd_errors
+from . import ClusterConfig, Cluster, Failover, Leader, Member, SyncState, \
+    TimelineHistory, catch_return_false_exception, citus_group_re
+from .etcd import AbstractEtcdClientWithFailover, AbstractEtcd, catch_etcd_errors, DnsCachingResolver, Retry
 from ..exceptions import DCSError, PatroniException
 from ..utils import deep_compare, enable_keepalive, iter_response_objects, RetryFailedError, USER_AGENT
 
@@ -31,11 +33,27 @@ class UnsupportedEtcdVersion(PatroniException):
 
 
 # google.golang.org/grpc/codes
-GRPCCode = type('Enum', (), {'OK': 0, 'Canceled': 1, 'Unknown': 2, 'InvalidArgument': 3, 'DeadlineExceeded': 4,
-                             'NotFound': 5, 'AlreadyExists': 6, 'PermissionDenied': 7, 'ResourceExhausted': 8,
-                             'FailedPrecondition': 9, 'Aborted': 10, 'OutOfRange': 11, 'Unimplemented': 12,
-                             'Internal': 13, 'Unavailable': 14, 'DataLoss': 15, 'Unauthenticated': 16})
-GRPCcodeToText = {v: k for k, v in GRPCCode.__dict__.items() if not k.startswith('__') and isinstance(v, int)}
+class GRPCCode(IntEnum):
+    OK = 0
+    Canceled = 1
+    Unknown = 2
+    InvalidArgument = 3
+    DeadlineExceeded = 4
+    NotFound = 5
+    AlreadyExists = 6
+    PermissionDenied = 7
+    ResourceExhausted = 8
+    FailedPrecondition = 9
+    Aborted = 10
+    OutOfRange = 11
+    Unimplemented = 12
+    Internal = 13
+    Unavailable = 14
+    DataLoss = 15
+    Unauthenticated = 16
+
+
+GRPCcodeToText: Dict[int, str] = {v: k for k, v in GRPCCode.__dict__['_member_map_'].items()}
 
 
 class Etcd3Exception(etcd.EtcdException):
@@ -44,22 +62,24 @@ class Etcd3Exception(etcd.EtcdException):
 
 class Etcd3ClientError(Etcd3Exception):
 
-    def __init__(self, code=None, error=None, status=None):
+    def __init__(self, code: Optional[int] = None, error: Optional[str] = None, status: Optional[int] = None) -> None:
         if not hasattr(self, 'error'):
             self.error = error and error.strip()
-        self.codeText = GRPCcodeToText.get(code)
+        self.codeText = GRPCcodeToText.get(code) if code is not None else None
         self.status = status
 
-    def __repr__(self):
-        return "<{0} error: '{1}', code: {2}>".format(self.__class__.__name__, self.error, self.code)
+    def __repr__(self) -> str:
+        return "<{0} error: '{1}', code: {2}>"\
+            .format(self.__class__.__name__, getattr(self, 'error', None), getattr(self, 'code', None))
 
     __str__ = __repr__
 
-    def as_dict(self):
-        return {'error': self.error, 'code': self.code, 'codeText': self.codeText, 'status': self.status}
+    def as_dict(self) -> Dict[str, Any]:
+        return {'error': getattr(self, 'error', None), 'code': getattr(self, 'code', None),
+                'codeText': self.codeText, 'status': self.status}
 
     @classmethod
-    def get_subclasses(cls):
+    def get_subclasses(cls) -> Iterator[Type['Etcd3ClientError']]:
         for subclass in cls.__subclasses__():
             for subsubclass in subclass.get_subclasses():
                 yield subsubclass
@@ -118,63 +138,75 @@ class InvalidAuthToken(Etcd3ClientError):
     error = "etcdserver: invalid auth token"
 
 
-errStringToClientError = {s.error: s for s in Etcd3ClientError.get_subclasses() if hasattr(s, 'error')}
-errCodeToClientError = {s.code: s for s in Etcd3ClientError.__subclasses__()}
+errStringToClientError = {getattr(s, 'error'): s for s in Etcd3ClientError.get_subclasses() if hasattr(s, 'error')}
+errCodeToClientError = {getattr(s, 'code'): s for s in Etcd3ClientError.__subclasses__()}
 
 
-def _raise_for_data(data, status_code=None):
+def _raise_for_data(data: Union[bytes, str, Dict[str, Union[Any, Dict[str, Any]]]],
+                    status_code: Optional[int] = None) -> Etcd3ClientError:
     try:
-        error = data.get('error') or data.get('Error')
-        if isinstance(error, dict):  # streaming response
-            status_code = error.get('http_code')
-            code = error['grpc_code']
-            error = error['message']
+        if TYPE_CHECKING:  # pragma: no cover
+            assert isinstance(data, dict)
+        data_error: Optional[Dict[str, Any]] = data.get('error') or data.get('Error')
+        if isinstance(data_error, dict):  # streaming response
+            status_code = data_error.get('http_code')
+            code: Optional[int] = data_error['grpc_code']
+            error: str = data_error['message']
         else:
-            code = data.get('code') or data.get('Code')
+            data_code = data.get('code') or data.get('Code')
+            if TYPE_CHECKING:  # pragma: no cover
+                assert not isinstance(data_code, dict)
+            code = data_code
+            error = str(data_error)
     except Exception:
         error = str(data)
         code = GRPCCode.Unknown
     err = errStringToClientError.get(error) or errCodeToClientError.get(code) or Unknown
-    raise err(code, error, status_code)
+    return err(code, error, status_code)
 
 
-def to_bytes(v):
+def to_bytes(v: Union[str, bytes]) -> bytes:
     return v if isinstance(v, bytes) else v.encode('utf-8')
 
 
-def prefix_range_end(v):
-    v = bytearray(to_bytes(v))
-    for i in range(len(v) - 1, -1, -1):
-        if v[i] < 0xff:
-            v[i] += 1
+def prefix_range_end(v: str) -> bytes:
+    ret = bytearray(to_bytes(v))
+    for i in range(len(ret) - 1, -1, -1):
+        if ret[i] < 0xff:
+            ret[i] += 1
             break
-    return bytes(v)
+    return bytes(ret)
 
 
-def base64_encode(v):
+def base64_encode(v: Union[str, bytes]) -> str:
     return base64.b64encode(to_bytes(v)).decode('utf-8')
 
 
-def base64_decode(v):
+def base64_decode(v: str) -> str:
     return base64.b64decode(v).decode('utf-8')
 
 
-def build_range_request(key, range_end=None):
+def build_range_request(key: str, range_end: Union[bytes, str, None] = None) -> Dict[str, Any]:
     fields = {'key': base64_encode(key)}
     if range_end:
         fields['range_end'] = base64_encode(range_end)
     return fields
 
 
+def _handle_auth_errors(func: Callable[..., Any]) -> Any:
+    def wrapper(self: 'Etcd3Client', *args: Any, **kwargs: Any) -> Any:
+        return self.handle_auth_errors(func, *args, **kwargs)
+    return wrapper
+
+
 class Etcd3Client(AbstractEtcdClientWithFailover):
 
     ERROR_CLS = Etcd3Error
 
-    def __init__(self, config, dns_resolver, cache_ttl=300):
+    def __init__(self, config: Dict[str, Any], dns_resolver: DnsCachingResolver, cache_ttl: int = 300) -> None:
         self._token = None
-        self._cluster_version = None
-        self.version_prefix = '/v3beta'
-        super(Etcd3Client, self).__init__(config, dns_resolver, cache_ttl)
+        self._cluster_version: Tuple[int, ...] = tuple()
+        super(Etcd3Client, self).__init__({**config, 'version_prefix': '/v3beta'}, dns_resolver, cache_ttl)
 
         try:
             self.authenticate()
@@ -182,32 +214,33 @@ class Etcd3Client(AbstractEtcdClientWithFailover):
             logger.fatal('Etcd3 authentication failed: %r', e)
             sys.exit(1)
 
-    def _get_headers(self):
+    def _get_headers(self) -> Dict[str, str]:
         headers = urllib3.make_headers(user_agent=USER_AGENT)
         if self._token and self._cluster_version >= (3, 3, 0):
             headers['authorization'] = self._token
         return headers
 
-    def _prepare_request(self, kwargs, params=None, method=None):
+    def _prepare_request(self, kwargs: Dict[str, Any], params: Optional[Dict[str, Any]] = None,
+                         method: Optional[str] = None) -> Callable[..., urllib3.response.HTTPResponse]:
         if params is not None:
             kwargs['body'] = json.dumps(params)
             kwargs['headers']['Content-Type'] = 'application/json'
         return self.http.urlopen
 
-    @staticmethod
-    def _handle_server_response(response):
+    def _handle_server_response(self, response: urllib3.response.HTTPResponse) -> Dict[str, Any]:
         data = response.data
         try:
             data = data.decode('utf-8')
-            data = json.loads(data)
+            ret: Dict[str, Any] = json.loads(data)
+            if response.status < 400:
+                return ret
         except (TypeError, ValueError, UnicodeError) as e:
             if response.status < 400:
                 raise etcd.EtcdException('Server response was not valid JSON: %r' % e)
-        if response.status < 400:
-            return data
-        _raise_for_data(data, response.status)
+            ret = {}
+        raise _raise_for_data(ret or data, response.status)
 
-    def _ensure_version_prefix(self, base_uri, **kwargs):
+    def _ensure_version_prefix(self, base_uri: str, **kwargs: Any) -> None:
         if self.version_prefix != '/v3':
             response = self.http.urlopen(self._MGET, base_uri + '/version', **kwargs)
             response = self._handle_server_response(response)
@@ -234,87 +267,92 @@ class Etcd3Client(AbstractEtcdClientWithFailover):
             else:
                 self.version_prefix = '/v3'
 
-    def _prepare_get_members(self, etcd_nodes):
+    def _prepare_get_members(self, etcd_nodes: int) -> Dict[str, Any]:
         kwargs = self._prepare_common_parameters(etcd_nodes)
         self._prepare_request(kwargs, {})
         return kwargs
 
-    def _get_members(self, base_uri, **kwargs):
+    def _get_members(self, base_uri: str, **kwargs: Any) -> List[str]:
         self._ensure_version_prefix(base_uri, **kwargs)
         resp = self.http.urlopen(self._MPOST, base_uri + self.version_prefix + '/cluster/member/list', **kwargs)
         members = self._handle_server_response(resp)['members']
-        return set(url for member in members for url in member.get('clientURLs', []))
+        return [url for member in members for url in member.get('clientURLs', [])]
 
-    def call_rpc(self, method, fields, retry=None):
+    def call_rpc(self, method: str, fields: Dict[str, Any], retry: Optional[Retry] = None) -> Dict[str, Any]:
         fields['retry'] = retry
         return self.api_execute(self.version_prefix + method, self._MPOST, fields)
 
-    def authenticate(self):
-        if self._use_proxies and self._cluster_version is None:
+    def authenticate(self) -> bool:
+        if self._use_proxies and not self._cluster_version:
             kwargs = self._prepare_common_parameters(1)
             self._ensure_version_prefix(self._base_uri, **kwargs)
-        if self._cluster_version >= (3, 3) and self.username and self.password:
-            logger.info('Trying to authenticate on Etcd...')
-            old_token, self._token = self._token, None
-            try:
-                response = self.call_rpc('/auth/authenticate', {'name': self.username, 'password': self.password})
-            except AuthNotEnabled:
-                logger.info('Etcd authentication is not enabled')
-                self._token = None
-            except Exception:
-                self._token = old_token
-                raise
-            else:
-                self._token = response.get('token')
-            return old_token != self._token
+        if not (self._cluster_version >= (3, 3) and self.username and self.password):
+            return False
+        logger.info('Trying to authenticate on Etcd...')
+        old_token, self._token = self._token, None
+        try:
+            response = self.call_rpc('/auth/authenticate', {'name': self.username, 'password': self.password})
+        except AuthNotEnabled:
+            logger.info('Etcd authentication is not enabled')
+            self._token = None
+        except Exception:
+            self._token = old_token
+            raise
+        else:
+            self._token = response.get('token')
+        return old_token != self._token
 
-    def _handle_auth_errors(func):
-        def wrapper(self, *args, **kwargs):
-            def retry(ex):
-                if self.username and self.password:
-                    self.authenticate()
-                    return func(self, *args, **kwargs)
-                else:
-                    logger.fatal('Username or password not set, authentication is not possible')
-                    raise ex
-
-            try:
+    def handle_auth_errors(self: 'Etcd3Client', func: Callable[..., Any], *args: Any, **kwargs: Any) -> Any:
+        def retry(ex: Exception) -> Any:
+            if self.username and self.password:
+                self.authenticate()
                 return func(self, *args, **kwargs)
-            except (UserEmpty, PermissionDenied) as e:  # no token provided
-                # PermissionDenied is raised on 3.0 and 3.1
-                if self._cluster_version < (3, 3) and (not isinstance(e, PermissionDenied)
-                                                       or self._cluster_version < (3, 2)):
-                    raise UnsupportedEtcdVersion('Authentication is required by Etcd cluster but not '
-                                                 'supported on version lower than 3.3.0. Cluster version: '
-                                                 '{0}'.format('.'.join(map(str, self._cluster_version))))
-                return retry(e)
-            except InvalidAuthToken as e:
-                logger.error('Invalid auth token: %s', self._token)
-                return retry(e)
+            else:
+                logger.fatal('Username or password not set, authentication is not possible')
+                raise ex
 
-        return wrapper
+        try:
+            return func(self, *args, **kwargs)
+        except (UserEmpty, PermissionDenied) as e:  # no token provided
+            # PermissionDenied is raised on 3.0 and 3.1
+            if self._cluster_version < (3, 3) and (not isinstance(e, PermissionDenied)
+                                                   or self._cluster_version < (3, 2)):
+                raise UnsupportedEtcdVersion('Authentication is required by Etcd cluster but not '
+                                             'supported on version lower than 3.3.0. Cluster version: '
+                                             '{0}'.format('.'.join(map(str, self._cluster_version))))
+            return retry(e)
+        except InvalidAuthToken as e:
+            logger.error('Invalid auth token: %s', self._token)
+            return retry(e)
 
     @_handle_auth_errors
-    def range(self, key, range_end=None, retry=None):
+    def range(self, key: str, range_end: Union[bytes, str, None] = None, serializable: bool = True,
+              retry: Optional[Retry] = None) -> Dict[str, Any]:
         params = build_range_request(key, range_end)
-        params['serializable'] = True  # For better performance. We can tolerate stale reads.
+        params['serializable'] = serializable  # For better performance. We can tolerate stale reads
         return self.call_rpc('/kv/range', params, retry)
 
-    def prefix(self, key, retry=None):
-        return self.range(key, prefix_range_end(key), retry)
+    def prefix(self, key: str, serializable: bool = True, retry: Optional[Retry] = None) -> Dict[str, Any]:
+        return self.range(key, prefix_range_end(key), serializable, retry)
 
     @_handle_auth_errors
-    def lease_grant(self, ttl, retry=None):
+    def lease_grant(self, ttl: int, retry: Optional[Retry] = None) -> str:
         return self.call_rpc('/lease/grant', {'TTL': ttl}, retry)['ID']
 
-    def lease_keepalive(self, ID, retry=None):
+    def lease_keepalive(self, ID: str, retry: Optional[Retry] = None) -> Optional[str]:
         return self.call_rpc('/lease/keepalive', {'ID': ID}, retry).get('result', {}).get('TTL')
 
-    def txn(self, compare, success, retry=None):
-        return self.call_rpc('/kv/txn', {'compare': [compare], 'success': [success]}, retry).get('succeeded')
+    def txn(self, compare: Dict[str, Any], success: Dict[str, Any],
+            failure: Optional[Dict[str, Any]] = None, retry: Optional[Retry] = None) -> Dict[str, Any]:
+        fields = {'compare': [compare], 'success': [success]}
+        if failure:
+            fields['failure'] = [failure]
+        ret = self.call_rpc('/kv/txn', fields, retry)
+        return ret if failure or ret.get('succeeded') else {}
 
     @_handle_auth_errors
-    def put(self, key, value, lease=None, create_revision=None, mod_revision=None, retry=None):
+    def put(self, key: str, value: str, lease: Optional[str] = None, create_revision: Optional[str] = None,
+            mod_revision: Optional[str] = None, retry: Optional[Retry] = None) -> Dict[str, Any]:
         fields = {'key': base64_encode(key), 'value': base64_encode(value)}
         if lease:
             fields['lease'] = lease
@@ -325,20 +363,23 @@ class Etcd3Client(AbstractEtcdClientWithFailover):
         else:
             return self.call_rpc('/kv/put', fields, retry)
         compare['key'] = fields['key']
-        return self.txn(compare, {'request_put': fields}, retry)
+        return self.txn(compare, {'request_put': fields}, retry=retry)
 
     @_handle_auth_errors
-    def deleterange(self, key, range_end=None, mod_revision=None, retry=None):
+    def deleterange(self, key: str, range_end: Union[bytes, str, None] = None,
+                    mod_revision: Optional[str] = None, retry: Optional[Retry] = None) -> Dict[str, Any]:
         fields = build_range_request(key, range_end)
         if mod_revision is None:
             return self.call_rpc('/kv/deleterange', fields, retry)
         compare = {'target': 'MOD', 'mod_revision': mod_revision, 'key': fields['key']}
-        return self.txn(compare, {'request_delete_range': fields}, retry)
+        return self.txn(compare, {'request_delete_range': fields}, retry=retry)
 
-    def deleteprefix(self, key, retry=None):
+    def deleteprefix(self, key: str, retry: Optional[Retry] = None) -> Dict[str, Any]:
         return self.deleterange(key, prefix_range_end(key), retry=retry)
 
-    def watchrange(self, key, range_end=None, start_revision=None, filters=None, read_timeout=None):
+    def watchrange(self, key: str, range_end: Union[bytes, str, None] = None,
+                   start_revision: Optional[str] = None, filters: Optional[List[Dict[str, Any]]] = None,
+                   read_timeout: Optional[float] = None) -> urllib3.response.HTTPResponse:
         """returns: response object"""
         params = build_range_request(key, range_end)
         if start_revision is not None:
@@ -349,14 +390,16 @@ class Etcd3Client(AbstractEtcdClientWithFailover):
         kwargs.update(timeout=urllib3.Timeout(connect=kwargs['timeout'], read=read_timeout), retries=0)
         return request_executor(self._MPOST, self._base_uri + self.version_prefix + '/watch', **kwargs)
 
-    def watchprefix(self, key, start_revision=None, filters=None, read_timeout=None):
+    def watchprefix(self, key: str, start_revision: Optional[str] = None,
+                    filters: Optional[List[Dict[str, Any]]] = None,
+                    read_timeout: Optional[float] = None) -> urllib3.response.HTTPResponse:
         return self.watchrange(key, prefix_range_end(key), start_revision, filters, read_timeout)
 
 
 class KVCache(Thread):
 
-    def __init__(self, dcs, client):
-        Thread.__init__(self)
+    def __init__(self, dcs: 'Etcd3', client: 'PatroniEtcd3Client') -> None:
+        super(KVCache, self).__init__()
         self.daemon = True
         self._dcs = dcs
         self._client = client
@@ -365,7 +408,7 @@ class KVCache(Thread):
         self._leader_key = base64_encode(dcs.leader_path)
         self._optime_key = base64_encode(dcs.leader_optime_path)
         self._status_key = base64_encode(dcs.status_path)
-        self._name = base64_encode(dcs._name)
+        self._name = base64_encode(getattr(dcs, '_name'))  # pyright
         self._is_ready = False
         self._response = None
         self._response_lock = Lock()
@@ -373,32 +416,32 @@ class KVCache(Thread):
         self._object_cache_lock = Lock()
         self.start()
 
-    def set(self, value, overwrite=False):
+    def set(self, value: Dict[str, Any], overwrite: bool = False) -> Tuple[bool, Optional[Dict[str, Any]]]:
         with self._object_cache_lock:
             name = value['key']
             old_value = self._object_cache.get(name)
             ret = not old_value or int(old_value['mod_revision']) < int(value['mod_revision'])
-            if ret or overwrite and old_value['mod_revision'] == value['mod_revision']:
+            if ret or overwrite and old_value and old_value['mod_revision'] == value['mod_revision']:
                 self._object_cache[name] = value
         return ret, old_value
 
-    def delete(self, name, mod_revision):
+    def delete(self, name: str, mod_revision: str) -> Tuple[bool, Optional[Dict[str, Any]]]:
         with self._object_cache_lock:
             old_value = self._object_cache.get(name)
             ret = old_value and int(old_value['mod_revision']) < int(mod_revision)
             if ret:
                 del self._object_cache[name]
-        return not old_value or ret, old_value
+        return bool(not old_value or ret), old_value
 
-    def copy(self):
+    def copy(self) -> List[Dict[str, Any]]:
         with self._object_cache_lock:
             return [v.copy() for v in self._object_cache.values()]
 
-    def get(self, name):
+    def get(self, name: str) -> Optional[Dict[str, Any]]:
         with self._object_cache_lock:
             return self._object_cache.get(name)
 
-    def _process_event(self, event):
+    def _process_event(self, event: Dict[str, Any]) -> None:
         kv = event['kv']
         key = kv['key']
         if event.get('type') == 'DELETE':
@@ -411,32 +454,33 @@ class KVCache(Thread):
             new_value = kv.get('value')
 
             value_changed = old_value != new_value and \
-                (key == self._leader_key or key in (self._optime_key, self._status_key) and new_value is not None or
-                 key == self._config_key and old_value is not None and new_value is not None)
+                (key == self._leader_key or key in (self._optime_key, self._status_key) and new_value is not None
+                 or key == self._config_key and old_value is not None and new_value is not None)
 
             if value_changed:
                 logger.debug('%s changed from %s to %s', key, old_value, new_value)
 
             # We also want to wake up HA loop on replicas if leader optime (or status key) was updated
-            if value_changed and (key not in (self._optime_key, self._status_key) or
-                                  (self.get(self._leader_key) or {}).get('value') != self._name):
+            if value_changed and (key not in (self._optime_key, self._status_key)
+                                  or (self.get(self._leader_key) or {}).get('value') != self._name):
                 self._dcs.event.set()
 
-    def _process_message(self, message):
+    def _process_message(self, message: Dict[str, Any]) -> None:
         logger.debug('Received message: %s', message)
         if 'error' in message:
-            _raise_for_data(message)
-        for event in message.get('result', {}).get('events', []):
+            raise _raise_for_data(message)
+        events: List[Dict[str, Any]] = message.get('result', {}).get('events', [])
+        for event in events:
             self._process_event(event)
 
     @staticmethod
-    def _finish_response(response):
+    def _finish_response(response: urllib3.response.HTTPResponse) -> None:
         try:
             response.close()
         finally:
             response.release_conn()
 
-    def _do_watch(self, revision):
+    def _do_watch(self, revision: str) -> None:
         with self._response_lock:
             self._response = None
         # We do most of requests with timeouts. The only exception /watch requests to Etcd v3.
@@ -457,7 +501,7 @@ class KVCache(Thread):
         for message in iter_response_objects(response):
             self._process_message(message)
 
-    def _build_cache(self):
+    def _build_cache(self) -> None:
         result = self._dcs.retry(self._client.prefix, self._dcs.cluster_prefix)
         with self._object_cache_lock:
             self._object_cache = {node['key']: node for node in result.get('kvs', [])}
@@ -476,10 +520,10 @@ class KVCache(Thread):
                 self._is_ready = False
             with self._response_lock:
                 response, self._response = self._response, None
-            if response:
+            if isinstance(response, urllib3.response.HTTPResponse):
                 self._finish_response(response)
 
-    def run(self):
+    def run(self) -> None:
         while True:
             try:
                 self._build_cache()
@@ -487,12 +531,12 @@ class KVCache(Thread):
                 logger.error('KVCache.run %r', e)
                 time.sleep(1)
 
-    def kill_stream(self):
+    def kill_stream(self) -> None:
         sock = None
         with self._response_lock:
-            if self._response:
+            if isinstance(self._response, urllib3.response.HTTPResponse):
                 try:
-                    sock = self._response.connection.sock
+                    sock = self._response.connection.sock if self._response.connection else None
                 except Exception:
                     sock = None
             else:
@@ -504,65 +548,72 @@ class KVCache(Thread):
             except Exception as e:
                 logger.debug('Error on socket.shutdown: %r', e)
 
-    def is_ready(self):
+    def is_ready(self) -> bool:
         """Must be called only when holding the lock on `condition`"""
         return self._is_ready
 
 
 class PatroniEtcd3Client(Etcd3Client):
 
-    def __init__(self, *args, **kwargs):
+    def __init__(self, *args: Any, **kwargs: Any) -> None:
         self._kv_cache = None
         super(PatroniEtcd3Client, self).__init__(*args, **kwargs)
 
-    def configure(self, etcd3):
+    def configure(self, etcd3: 'Etcd3') -> None:
         self._etcd3 = etcd3
 
-    def start_watcher(self):
+    def start_watcher(self) -> None:
         if self._cluster_version >= (3, 1):
             self._kv_cache = KVCache(self._etcd3, self)
 
-    def _restart_watcher(self):
+    def _restart_watcher(self) -> None:
         if self._kv_cache:
             self._kv_cache.kill_stream()
 
-    def set_base_uri(self, value):
+    def set_base_uri(self, value: str) -> None:
         super(PatroniEtcd3Client, self).set_base_uri(value)
         self._restart_watcher()
 
-    def authenticate(self):
+    def authenticate(self) -> bool:
         ret = super(PatroniEtcd3Client, self).authenticate()
         if ret:
             self._restart_watcher()
         return ret
 
-    def _wait_cache(self, timeout):
+    def _wait_cache(self, timeout: float) -> None:
         stop_time = time.time() + timeout
-        while not self._kv_cache.is_ready():
+        while self._kv_cache and not self._kv_cache.is_ready():
             timeout = stop_time - time.time()
             if timeout <= 0:
                 raise RetryFailedError('Exceeded retry deadline')
             self._kv_cache.condition.wait(timeout)
 
-    def get_cluster(self, path):
+    def get_cluster(self, path: str) -> List[Dict[str, Any]]:
         if self._kv_cache and path.startswith(self._etcd3.cluster_prefix):
             with self._kv_cache.condition:
-                self._wait_cache(self._etcd3._retry.deadline)
+                self._wait_cache(self.read_timeout)
                 ret = self._kv_cache.copy()
         else:
-            ret = self._etcd3.retry(self.prefix, path).get('kvs', [])
+            serializable = not getattr(self._etcd3, '_ctl')  # use linearizable for patronictl
+            ret = self._etcd3.retry(self.prefix, path, serializable).get('kvs', [])
         for node in ret:
             node.update({'key': base64_decode(node['key']),
                          'value': base64_decode(node.get('value', '')),
                          'lease': node.get('lease')})
         return ret
 
-    def call_rpc(self, method, fields, retry=None):
+    def call_rpc(self, method: str, fields: Dict[str, Any], retry: Optional[Retry] = None) -> Dict[str, Any]:
         ret = super(PatroniEtcd3Client, self).call_rpc(method, fields, retry)
 
         if self._kv_cache:
             value = delete = None
-            if method == '/kv/txn' and ret.get('succeeded'):
+            # For the 'failure' case we only support a second (nested) transaction that attempts to
+            # update/delete the same keys. Anything more complex than that we don't need and therefore it doesn't
+            # make sense to write a universal response analyzer and we can just check expected JSON path.
+            if method == '/kv/txn'\
+                    and (ret.get('succeeded') or 'failure' in fields and 'request_txn' in fields['failure'][0]
+                         and ret.get('responses', [{'response_txn': {'succeeded': False}}])[0]
+                         .get('response_txn', {}).get('succeeded')):
                 on_success = fields['success'][0]
                 value = on_success.get('request_put')
                 delete = on_success.get('request_delete_range')
@@ -579,10 +630,20 @@ class PatroniEtcd3Client(Etcd3Client):
 
         return ret
 
+    def txn(self, compare: Dict[str, Any], success: Dict[str, Any],
+            failure: Optional[Dict[str, Any]] = None, retry: Optional[Retry] = None) -> Dict[str, Any]:
+        ret = super(PatroniEtcd3Client, self).txn(compare, success, failure, retry)
+        # Here we abuse the fact that the `failure` is only set in the call from update_leader().
+        # In all other cases the txn() call failure may be an indicator of a stale cache,
+        # and therefore we want to restart watcher.
+        if not failure and not ret:
+            self._restart_watcher()
+        return ret
+
 
 class Etcd3(AbstractEtcd):
 
-    def __init__(self, config):
+    def __init__(self, config: Dict[str, Any]) -> None:
         super(Etcd3, self).__init__(config, PatroniEtcd3Client, (DeadlineExceeded, Unavailable, FailedPrecondition))
         self.__do_not_watch = False
         self._lease = None
@@ -593,15 +654,25 @@ class Etcd3(AbstractEtcd):
             self._client.start_watcher()
             self.create_lease()
 
-    def set_socket_options(self, sock, socket_options):
+    @property
+    def _client(self) -> PatroniEtcd3Client:
+        if TYPE_CHECKING:  # pragma: no cover
+            assert isinstance(self._abstract_client, PatroniEtcd3Client)
+        return self._abstract_client
+
+    def set_socket_options(self, sock: socket.socket,
+                           socket_options: Optional[Collection[Tuple[int, int, int]]]) -> None:
+        if TYPE_CHECKING:  # pragma: no cover
+            assert self._retry.deadline is not None
         enable_keepalive(sock, self.ttl, int(self.loop_wait + self._retry.deadline))
 
-    def set_ttl(self, ttl):
+    def set_ttl(self, ttl: int) -> Optional[bool]:
         self.__do_not_watch = super(Etcd3, self).set_ttl(ttl)
         if self.__do_not_watch:
             self._lease = None
+        return None
 
-    def _do_refresh_lease(self, force=False, retry=None):
+    def _do_refresh_lease(self, force: bool = False, retry: Optional[Retry] = None) -> bool:
         if not force and self._lease and self._last_lease_refresh + self._loop_wait > time.time():
             return False
 
@@ -615,14 +686,14 @@ class Etcd3(AbstractEtcd):
         self._last_lease_refresh = time.time()
         return ret
 
-    def refresh_lease(self):
+    def refresh_lease(self) -> bool:
         try:
             return self.retry(self._do_refresh_lease)
         except (Etcd3ClientError, RetryFailedError):
             logger.exception('refresh_lease')
         raise Etcd3Error('Failed to keepalive/grant lease')
 
-    def create_lease(self):
+    def create_lease(self) -> None:
         while not self._lease:
             try:
                 self.refresh_lease()
@@ -631,14 +702,14 @@ class Etcd3(AbstractEtcd):
                 time.sleep(5)
 
     @property
-    def cluster_prefix(self):
+    def cluster_prefix(self) -> str:
         return self._base_path + '/' if self.is_citus_coordinator() else self.client_path('')
 
     @staticmethod
-    def member(node):
+    def member(node: Dict[str, str]) -> Member:
         return Member.from_node(node['mod_revision'], os.path.basename(node['key']), node['lease'], node['value'])
 
-    def _cluster_from_nodes(self, nodes):
+    def _cluster_from_nodes(self, nodes: Dict[str, Any]) -> Cluster:
         # get initialize flag
         initialize = nodes.get(self._INITIALIZE)
         initialize = initialize and initialize['value']
@@ -666,7 +737,7 @@ class Etcd3(AbstractEtcd):
             slots = None
 
         try:
-            last_lsn = int(last_lsn)
+            last_lsn = int(last_lsn or '')
         except Exception:
             last_lsn = 0
 
@@ -701,14 +772,14 @@ class Etcd3(AbstractEtcd):
 
         return Cluster(initialize, config, leader, last_lsn, members, failover, sync, history, slots, failsafe)
 
-    def _cluster_loader(self, path):
+    def _cluster_loader(self, path: str) -> Cluster:
         nodes = {node['key'][len(path):]: node
                  for node in self._client.get_cluster(path)
                  if node['key'].startswith(path)}
         return self._cluster_from_nodes(nodes)
 
-    def _citus_cluster_loader(self, path):
-        clusters = defaultdict(dict)
+    def _citus_cluster_loader(self, path: str) -> Dict[int, Cluster]:
+        clusters: Dict[int, Dict[str, Dict[str, Any]]] = defaultdict(dict)
         path = self._base_path + '/'
         for node in self._client.get_cluster(path):
             key = node['key'][len(path):].split('/', 1)
@@ -716,7 +787,9 @@ class Etcd3(AbstractEtcd):
                 clusters[int(key[0])][key[1]] = node
         return {group: self._cluster_from_nodes(nodes) for group, nodes in clusters.items()}
 
-    def _load_cluster(self, path, loader):
+    def _load_cluster(
+            self, path: str, loader: Callable[[str], Union[Cluster, Dict[int, Cluster]]]
+    ) -> Union[Cluster, Dict[int, Cluster]]:
         cluster = None
         try:
             cluster = loader(path)
@@ -725,10 +798,12 @@ class Etcd3(AbstractEtcd):
         except Exception as e:
             self._handle_exception(e, 'get_cluster', raise_ex=Etcd3Error('Etcd is not responding properly'))
         self._has_failed = False
+        if TYPE_CHECKING:  # pragma: no cover
+            assert cluster is not None
         return cluster
 
     @catch_etcd_errors
-    def touch_member(self, data):
+    def touch_member(self, data: Dict[str, Any]) -> bool:
         try:
             self.refresh_lease()
         except Etcd3Error:
@@ -740,50 +815,47 @@ class Etcd3(AbstractEtcd):
         if member and member.session == self._lease and deep_compare(data, member.data):
             return True
 
-        data = json.dumps(data, separators=(',', ':'))
+        value = json.dumps(data, separators=(',', ':'))
         try:
-            return self._client.put(self.member_path, data, self._lease)
+            return bool(self._client.put(self.member_path, value, self._lease))
         except LeaseNotFound:
             self._lease = None
             logger.error('Our lease disappeared from Etcd, can not "touch_member"')
+        return False
 
     @catch_etcd_errors
-    def take_leader(self):
+    def take_leader(self) -> bool:
         return self.retry(self._client.put, self.leader_path, self._name, self._lease)
 
-    def _do_attempt_to_acquire_leader(self, retry):
-        def _retry(*args, **kwargs):
+    def _do_attempt_to_acquire_leader(self, retry: Retry) -> bool:
+        def _retry(*args: Any, **kwargs: Any) -> Any:
             kwargs['retry'] = retry
             return retry(*args, **kwargs)
 
         try:
-            return _retry(self._client.put, self.leader_path, self._name, self._lease, 0)
+            return _retry(self._client.put, self.leader_path, self._name, self._lease, create_revision='0')
         except LeaseNotFound:
             logger.error('Our lease disappeared from Etcd. Will try to get a new one and retry attempt')
             self._lease = None
-            retry.deadline = retry.stoptime - time.time()
+            retry.ensure_deadline(0)
 
             _retry(self._do_refresh_lease)
 
-            retry.deadline = retry.stoptime - time.time()
-            if retry.deadline < 1:
-                raise Etcd3Error('_do_attempt_to_acquire_leader timeout')
+            retry.ensure_deadline(1, Etcd3Error('_do_attempt_to_acquire_leader timeout'))
 
-            return _retry(self._client.put, self.leader_path, self._name, self._lease, 0)
+            return _retry(self._client.put, self.leader_path, self._name, self._lease, create_revision='0')
 
     @catch_return_false_exception
-    def attempt_to_acquire_leader(self):
+    def attempt_to_acquire_leader(self) -> bool:
         retry = self._retry.copy()
 
-        def _retry(*args, **kwargs):
+        def _retry(*args: Any, **kwargs: Any) -> Any:
             kwargs['retry'] = retry
             return retry(*args, **kwargs)
 
         self._run_and_handle_exceptions(self._do_refresh_lease, retry=_retry)
 
-        retry.deadline = retry.stoptime - time.time()
-        if retry.deadline < 1:
-            raise Etcd3Error('attempt_to_acquire_leader timeout')
+        retry.ensure_deadline(1, Etcd3Error('attempt_to_acquire_leader timeout'))
 
         ret = self._run_and_handle_exceptions(self._do_attempt_to_acquire_leader, retry, retry=None)
         if not ret:
@@ -791,85 +863,91 @@ class Etcd3(AbstractEtcd):
         return ret
 
     @catch_etcd_errors
-    def set_failover_value(self, value, index=None):
-        return self._client.put(self.failover_path, value, mod_revision=index)
+    def set_failover_value(self, value: str, version: Optional[str] = None) -> bool:
+        return bool(self._client.put(self.failover_path, value, mod_revision=version))
 
     @catch_etcd_errors
-    def set_config_value(self, value, index=None):
-        return self._client.put(self.config_path, value, mod_revision=index)
+    def set_config_value(self, value: str, version: Optional[str] = None) -> bool:
+        return bool(self._client.put(self.config_path, value, mod_revision=version))
 
     @catch_etcd_errors
-    def _write_leader_optime(self, last_lsn):
-        return self._client.put(self.leader_optime_path, last_lsn)
+    def _write_leader_optime(self, last_lsn: str) -> bool:
+        return bool(self._client.put(self.leader_optime_path, last_lsn))
 
     @catch_etcd_errors
-    def _write_status(self, value):
-        return self._client.put(self.status_path, value)
+    def _write_status(self, value: str) -> bool:
+        return bool(self._client.put(self.status_path, value))
 
     @catch_etcd_errors
-    def _write_failsafe(self, value):
-        return self._client.put(self.failsafe_path, value)
+    def _write_failsafe(self, value: str) -> bool:
+        return bool(self._client.put(self.failsafe_path, value))
 
     @catch_return_false_exception
-    def _update_leader(self):
+    def _update_leader(self, leader: Leader) -> bool:
         retry = self._retry.copy()
 
-        def _retry(*args, **kwargs):
+        def _retry(*args: Any, **kwargs: Any) -> Any:
             kwargs['retry'] = retry
             return retry(*args, **kwargs)
 
         self._run_and_handle_exceptions(self._do_refresh_lease, True, retry=_retry)
 
-        if self._lease:
-            cluster = self.cluster
-            leader_lease = cluster and isinstance(cluster.leader, Leader) and cluster.leader.session
-            if leader_lease != self._lease:
-                retry.deadline = retry.stoptime - time.time()
-                if retry.deadline < 1:
-                    raise Etcd3Error('update_leader timeout')
+        if self._lease and leader.session != self._lease:
+            retry.ensure_deadline(1, Etcd3Error('update_leader timeout'))
 
-                try:
-                    self._run_and_handle_exceptions(self._client.put, self.leader_path,
-                                                    self._name, self._lease, retry=_retry)
-                except ReturnFalseException:
-                    pass
+            fields = {'key': base64_encode(self.leader_path), 'value': base64_encode(self._name), 'lease': self._lease}
+            # First we try to update lease on existing leader key "hoping" that we still owning it
+            compare1 = {'key': fields['key'], 'target': 'VALUE', 'value': fields['value']}
+            request_put = {'request_put': fields}
+            # If the first comparison failed we will try to create the new leader key in a transaction
+            compare2 = {'key': fields['key'], 'target': 'CREATE', 'create_revision': '0'}
+            request_txn = {'request_txn': {'compare': [compare2], 'success': [request_put]}}
+            ret = self._run_and_handle_exceptions(self._client.txn, compare1, request_put, request_txn, retry=_retry)
+            return ret.get('succeeded', False)\
+                or ret.get('responses', [{}])[0].get('response_txn', {}).get('succeeded', False)
         return bool(self._lease)
 
     @catch_etcd_errors
-    def initialize(self, create_new=True, sysid=""):
-        return self.retry(self._client.put, self.initialize_path, sysid, None, 0 if create_new else None)
+    def initialize(self, create_new: bool = True, sysid: str = ""):
+        return self.retry(self._client.put, self.initialize_path, sysid, create_revision='0' if create_new else None)
 
     @catch_etcd_errors
-    def _delete_leader(self):
+    def _delete_leader(self) -> bool:
         cluster = self.cluster
         if cluster and isinstance(cluster.leader, Leader) and cluster.leader.name == self._name:
-            return self._client.deleterange(self.leader_path, mod_revision=cluster.leader.index)
+            return self._client.deleterange(self.leader_path, mod_revision=cluster.leader.version)
+        return True
 
     @catch_etcd_errors
-    def cancel_initialization(self):
+    def cancel_initialization(self) -> bool:
         return self.retry(self._client.deleterange, self.initialize_path)
 
     @catch_etcd_errors
-    def delete_cluster(self):
+    def delete_cluster(self) -> bool:
         return self.retry(self._client.deleteprefix, self.client_path(''))
 
     @catch_etcd_errors
-    def set_history_value(self, value):
-        return self._client.put(self.history_path, value)
+    def set_history_value(self, value: str) -> bool:
+        return bool(self._client.put(self.history_path, value))
 
     @catch_etcd_errors
-    def set_sync_state_value(self, value, index=None):
-        return self.retry(self._client.put, self.sync_path, value, mod_revision=index)
+    def set_sync_state_value(self, value: str, version: Optional[str] = None) -> Union[str, bool]:
+        return self.retry(self._client.put, self.sync_path, value, mod_revision=version)\
+            .get('header', {}).get('revision', False)
 
     @catch_etcd_errors
-    def delete_sync_state(self, index=None):
-        return self.retry(self._client.deleterange, self.sync_path, mod_revision=index)
+    def delete_sync_state(self, version: Optional[str] = None) -> bool:
+        return self.retry(self._client.deleterange, self.sync_path, mod_revision=version)
 
-    def watch(self, leader_index, timeout):
+    def watch(self, leader_version: Optional[str], timeout: float) -> bool:
         if self.__do_not_watch:
             self.__do_not_watch = False
             return True
 
+        # We want to give a bit more time to non-leader nodes to synchronize HA loops
+        if leader_version:
+            timeout += 0.5
+
         try:
             return super(Etcd3, self).watch(None, timeout)
         finally:

patroni/dcs/exhibitor.py

@@ -3,9 +3,12 @@ import logging
 import random
 import time
 
-from patroni.dcs.zookeeper import ZooKeeper
-from patroni.request import get as requests_get
-from patroni.utils import uri
+from typing import Any, Callable, Dict, List, Union
+
+from . import Cluster
+from .zookeeper import ZooKeeper
+from ..request import get as requests_get
+from ..utils import uri
 
 logger = logging.getLogger(__name__)
 
@@ -14,11 +17,12 @@ class ExhibitorEnsembleProvider(object):
 
     TIMEOUT = 3.1
 
-    def __init__(self, hosts, port, uri_path='/exhibitor/v1/cluster/list', poll_interval=300):
+    def __init__(self, hosts: List[str], port: int,
+                 uri_path: str = '/exhibitor/v1/cluster/list', poll_interval: int = 300) -> None:
         self._exhibitor_port = port
         self._uri_path = uri_path
         self._poll_interval = poll_interval
-        self._exhibitors = hosts
+        self._exhibitors: List[str] = hosts
         self._boot_exhibitors = hosts
         self._zookeeper_hosts = ''
         self._next_poll = None
@@ -26,7 +30,7 @@ class ExhibitorEnsembleProvider(object):
             logger.info('waiting on exhibitor')
             time.sleep(5)
 
-    def poll(self):
+    def poll(self) -> bool:
         if self._next_poll and self._next_poll > time.time():
             return False
 
@@ -36,7 +40,8 @@ class ExhibitorEnsembleProvider(object):
 
         if isinstance(json, dict) and 'servers' in json and 'port' in json:
             self._next_poll = time.time() + self._poll_interval
-            zookeeper_hosts = ','.join([h + ':' + str(json['port']) for h in sorted(json['servers'])])
+            servers: List[str] = json['servers']
+            zookeeper_hosts = ','.join([h + ':' + str(json['port']) for h in sorted(servers)])
             if self._zookeeper_hosts != zookeeper_hosts:
                 logger.info('ZooKeeper connection string has changed: %s => %s', self._zookeeper_hosts, zookeeper_hosts)
                 self._zookeeper_hosts = zookeeper_hosts
@@ -44,7 +49,7 @@ class ExhibitorEnsembleProvider(object):
                 return True
         return False
 
-    def _query_exhibitors(self, exhibitors):
+    def _query_exhibitors(self, exhibitors: List[str]) -> Union[Dict[str, Any], Any]:
         random.shuffle(exhibitors)
         for host in exhibitors:
             try:
@@ -55,18 +60,20 @@ class ExhibitorEnsembleProvider(object):
         return None
 
     @property
-    def zookeeper_hosts(self):
+    def zookeeper_hosts(self) -> str:
         return self._zookeeper_hosts
 
 
 class Exhibitor(ZooKeeper):
 
-    def __init__(self, config):
+    def __init__(self, config: Dict[str, Any]) -> None:
         interval = config.get('poll_interval', 300)
         self._ensemble_provider = ExhibitorEnsembleProvider(config['hosts'], config['port'], poll_interval=interval)
         super(Exhibitor, self).__init__({**config, 'hosts': self._ensemble_provider.zookeeper_hosts})
 
-    def _load_cluster(self, path, loader):
+    def _load_cluster(
+            self, path: str, loader: Callable[[str], Union[Cluster, Dict[int, Cluster]]]
+    ) -> Union[Cluster, Dict[int, Cluster]]:
         if self._ensemble_provider.poll():
             self._client.set_hosts(self._ensemble_provider.zookeeper_hosts)
         return super(Exhibitor, self)._load_cluster(path, loader)

patroni/dcs/raft.py

@@ -10,10 +10,13 @@ from pysyncobj.dns_resolver import globalDnsResolver
 from pysyncobj.node import TCPNode
 from pysyncobj.transport import TCPTransport, CONNECTION_STATE
 from pysyncobj.utility import TcpUtility
+from typing import Any, Callable, Collection, Dict, List, Optional, Set, Union, TYPE_CHECKING
 
 from . import AbstractDCS, ClusterConfig, Cluster, Failover, Leader, Member, SyncState, TimelineHistory, citus_group_re
 from ..exceptions import DCSError
 from ..utils import validate_directory
+if TYPE_CHECKING:  # pragma: no cover
+    from ..config import Config
 
 logger = logging.getLogger(__name__)
 
@@ -24,11 +27,12 @@ class RaftError(DCSError):
 
 class _TCPTransport(TCPTransport):
 
-    def __init__(self, syncObj, selfNode, otherNodes):
+    def __init__(self, syncObj: 'DynMemberSyncObj', selfNode: Optional[TCPNode],
+                 otherNodes: Collection[TCPNode]) -> None:
         super(_TCPTransport, self).__init__(syncObj, selfNode, otherNodes)
         self.setOnUtilityMessageCallback('members', syncObj.getMembers)
 
-    def _connectIfNecessarySingle(self, node):
+    def _connectIfNecessarySingle(self, node: TCPNode) -> bool:
         try:
             return super(_TCPTransport, self)._connectIfNecessarySingle(node)
         except Exception as e:
@@ -36,7 +40,7 @@ class _TCPTransport(TCPTransport):
             return False
 
 
-def resolve_host(self):
+def resolve_host(self: TCPNode) -> Optional[str]:
     return globalDnsResolver().resolve(self.host)
 
 
@@ -45,17 +49,19 @@ setattr(TCPNode, 'ip', property(resolve_host))
 
 class SyncObjUtility(object):
 
-    def __init__(self, otherNodes, conf, retry_timeout=10):
+    def __init__(self, otherNodes: Collection[Union[str, TCPNode]], conf: SyncObjConf, retry_timeout: int = 10) -> None:
         self._nodes = otherNodes
-        self._utility = TcpUtility(conf.password, retry_timeout/max(1, len(otherNodes)))
+        self._utility = TcpUtility(conf.password, retry_timeout / max(1, len(otherNodes)))
+        self.__node = next(iter(otherNodes), None)
 
-    def executeCommand(self, command):
+    def executeCommand(self, command: List[Any]) -> Any:
         try:
-            return self._utility.executeCommand(self.__node, command)
+            if self.__node:
+                return self._utility.executeCommand(self.__node, command)
         except Exception:
             return None
 
-    def getMembers(self):
+    def getMembers(self) -> Optional[List[str]]:
         for self.__node in self._nodes:
             response = self.executeCommand(['members'])
             if response:
@@ -64,7 +70,8 @@ class SyncObjUtility(object):
 
 class DynMemberSyncObj(SyncObj):
 
-    def __init__(self, selfAddress, partnerAddrs, conf, retry_timeout=10):
+    def __init__(self, selfAddress: Optional[str], partnerAddrs: Collection[str],
+                 conf: SyncObjConf, retry_timeout: int = 10) -> None:
         self.__early_apply_local_log = selfAddress is not None
         self.applied_local_log = False
 
@@ -81,12 +88,12 @@ class DynMemberSyncObj(SyncObj):
             thread.daemon = True
             thread.start()
 
-    def getMembers(self, args, callback):
+    def getMembers(self, args: Any, callback: Callable[[Any, Any], Any]) -> None:
         callback([{'addr': node.id, 'leader': node == self._getLeader(), 'status': CONNECTION_STATE.CONNECTED
-                   if self.isNodeConnected(node) else CONNECTION_STATE.DISCONNECTED} for node in self.otherNodes] +
-                 [{'addr': self.selfNode.id, 'leader': self._isLeader(), 'status': CONNECTION_STATE.CONNECTED}], None)
+                   if self.isNodeConnected(node) else CONNECTION_STATE.DISCONNECTED} for node in self.otherNodes]
+                 + [{'addr': self.selfNode.id, 'leader': self._isLeader(), 'status': CONNECTION_STATE.CONNECTED}], None)
 
-    def _onTick(self, timeToWait=0.0):
+    def _onTick(self, timeToWait: float = 0.0):
         super(DynMemberSyncObj, self)._onTick(timeToWait)
 
         # The SyncObj calls onReady callback only when cluster got the leader and is ready for writes.
@@ -98,15 +105,16 @@ class DynMemberSyncObj(SyncObj):
 
 class KVStoreTTL(DynMemberSyncObj):
 
-    def __init__(self, on_ready, on_set, on_delete, **config):
+    def __init__(self, on_ready: Optional[Callable[..., Any]], on_set: Optional[Callable[[str, Dict[str, Any]], None]],
+                 on_delete: Optional[Callable[[str], None]], **config: Any) -> None:
         self.__thread = None
         self.__on_set = on_set
         self.__on_delete = on_delete
-        self.__limb = {}
+        self.__limb: Dict[str, Dict[str, Any]] = {}
         self.set_retry_timeout(int(config.get('retry_timeout') or 10))
 
         self_addr = config.get('self_addr')
-        partner_addrs = set(config.get('partner_addrs', []))
+        partner_addrs: Set[str] = set(config.get('partner_addrs', []))
         if config.get('patronictl'):
             if self_addr:
                 partner_addrs.add(self_addr)
@@ -128,22 +136,22 @@ class KVStoreTTL(DynMemberSyncObj):
                            onReady=on_ready, dynamicMembershipChange=True)
 
         super(KVStoreTTL, self).__init__(self_addr, partner_addrs, conf, self.__retry_timeout)
-        self.__data = {}
+        self.__data: Dict[str, Dict[str, Any]] = {}
 
     @staticmethod
-    def __check_requirements(old_value, **kwargs):
-        return ('prevExist' not in kwargs or bool(kwargs['prevExist']) == bool(old_value)) and \
-            ('prevValue' not in kwargs or old_value and old_value['value'] == kwargs['prevValue']) and \
-            (not kwargs.get('prevIndex') or old_value and old_value['index'] == kwargs['prevIndex'])
+    def __check_requirements(old_value: Dict[str, Any], **kwargs: Any) -> bool:
+        return bool(('prevExist' not in kwargs or bool(kwargs['prevExist']) == bool(old_value))
+                    and ('prevValue' not in kwargs or old_value and old_value['value'] == kwargs['prevValue'])
+                    and (kwargs.get('prevIndex') is None or old_value and old_value['index'] == kwargs['prevIndex']))
 
-    def set_retry_timeout(self, retry_timeout):
+    def set_retry_timeout(self, retry_timeout: int) -> None:
         self.__retry_timeout = retry_timeout
 
-    def retry(self, func, *args, **kwargs):
+    def retry(self, func: Callable[..., Any], *args: Any, **kwargs: Any) -> Any:
         event = threading.Event()
         ret = {'result': None, 'error': -1}
 
-        def callback(result, error):
+        def callback(result: Any, error: Any) -> None:
             ret.update(result=result, error=error)
             event.set()
 
@@ -167,7 +175,7 @@ class KVStoreTTL(DynMemberSyncObj):
         return False
 
     @replicated
-    def _set(self, key, value, **kwargs):
+    def _set(self, key: str, value: Dict[str, Any], **kwargs: Any) -> Union[bool, Dict[str, Any]]:
         old_value = self.__data.get(key, {})
         if not self.__check_requirements(old_value, **kwargs):
             return False
@@ -179,31 +187,32 @@ class KVStoreTTL(DynMemberSyncObj):
         self.__data[key] = value
         if self.__on_set:
             self.__on_set(key, value)
-        return True
+        return value
 
-    def set(self, key, value, ttl=None, handle_raft_error=True, **kwargs):
+    def set(self, key: str, value: str, ttl: Optional[int] = None,
+            handle_raft_error: bool = True, **kwargs: Any) -> Union[bool, Dict[str, Any]]:
         old_value = self.__data.get(key, {})
         if not self.__check_requirements(old_value, **kwargs):
             return False
 
-        value = {'value': value, 'updated': time.time()}
-        value['created'] = old_value.get('created', value['updated'])
+        data: Dict[str, Any] = {'value': value, 'updated': time.time()}
+        data['created'] = old_value.get('created', data['updated'])
         if ttl:
-            value['expire'] = value['updated'] + ttl
+            data['expire'] = data['updated'] + ttl
         try:
-            return self.retry(self._set, key, value, **kwargs)
+            return self.retry(self._set, key, data, **kwargs)
         except RaftError:
             if not handle_raft_error:
                 raise
             return False
 
-    def __pop(self, key):
+    def __pop(self, key: str) -> None:
         self.__data.pop(key)
         if self.__on_delete:
             self.__on_delete(key)
 
     @replicated
-    def _delete(self, key, recursive=False, **kwargs):
+    def _delete(self, key: str, recursive: bool = False, **kwargs: Any) -> bool:
         if recursive:
             for k in list(self.__data.keys()):
                 if k.startswith(key):
@@ -214,7 +223,7 @@ class KVStoreTTL(DynMemberSyncObj):
             self.__pop(key)
         return True
 
-    def delete(self, key, recursive=False, **kwargs):
+    def delete(self, key: str, recursive: bool = False, **kwargs: Any) -> bool:
         if not recursive and not self.__check_requirements(self.__data.get(key, {}), **kwargs):
             return False
         try:
@@ -223,32 +232,32 @@ class KVStoreTTL(DynMemberSyncObj):
             return False
 
     @staticmethod
-    def __values_match(old, new):
+    def __values_match(old: Dict[str, Any], new: Dict[str, Any]) -> bool:
         return all(old.get(n) == new.get(n) for n in ('created', 'updated', 'expire', 'value'))
 
     @replicated
-    def _expire(self, key, value, callback=None):
+    def _expire(self, key: str, value: Dict[str, Any], callback: Optional[Callable[..., Any]] = None) -> None:
         current = self.__data.get(key)
         if current and self.__values_match(current, value):
             self.__pop(key)
 
-    def __expire_keys(self):
+    def __expire_keys(self) -> None:
         for key, value in self.__data.items():
             if value and 'expire' in value and value['expire'] <= time.time() and \
                     not (key in self.__limb and self.__values_match(self.__limb[key], value)):
                 self.__limb[key] = value
 
-                def callback(*args):
+                def callback(*args: Any) -> None:
                     if key in self.__limb and self.__values_match(self.__limb[key], value):
                         self.__limb.pop(key)
                 self._expire(key, value, callback=callback)
 
-    def get(self, key, recursive=False):
+    def get(self, key: str, recursive: bool = False) -> Union[None, Dict[str, Any], Dict[str, Dict[str, Any]]]:
         if not recursive:
             return self.__data.get(key)
         return {k: v for k, v in self.__data.items() if k.startswith(key)}
 
-    def _onTick(self, timeToWait=0.0):
+    def _onTick(self, timeToWait: float = 0.0) -> None:
         super(KVStoreTTL, self)._onTick(timeToWait)
 
         if self._isLeader():
@@ -256,17 +265,17 @@ class KVStoreTTL(DynMemberSyncObj):
         else:
             self.__limb.clear()
 
-    def _autoTickThread(self):
+    def _autoTickThread(self) -> None:
         self.__destroying = False
         while not self.__destroying:
             self.doTick(self.conf.autoTickPeriod)
 
-    def startAutoTick(self):
+    def startAutoTick(self) -> None:
         self.__thread = threading.Thread(target=self._autoTickThread)
         self.__thread.daemon = True
         self.__thread.start()
 
-    def destroy(self):
+    def destroy(self) -> None:
         if self.__thread:
             self.__destroying = True
             self.__thread.join()
@@ -275,7 +284,7 @@ class KVStoreTTL(DynMemberSyncObj):
 
 class Raft(AbstractDCS):
 
-    def __init__(self, config):
+    def __init__(self, config: Dict[str, Any]) -> None:
         super(Raft, self).__init__(config)
         self._ttl = int(config.get('ttl') or 30)
 
@@ -290,7 +299,7 @@ class Raft(AbstractDCS):
             else:
                 logger.info('waiting on raft')
 
-    def _on_set(self, key, value):
+    def _on_set(self, key: str, value: Dict[str, Any]) -> None:
         leader = (self._sync_obj.get(self.leader_path) or {}).get('value')
         if key == value['created'] == value['updated'] and \
                 (key.startswith(self.members_path) or key == self.leader_path and leader != self._name) or \
@@ -298,29 +307,29 @@ class Raft(AbstractDCS):
                 key in (self.config_path, self.sync_path):
             self.event.set()
 
-    def _on_delete(self, key):
+    def _on_delete(self, key: str) -> None:
         if key == self.leader_path:
             self.event.set()
 
-    def set_ttl(self, ttl):
+    def set_ttl(self, ttl: int) -> Optional[bool]:
         self._ttl = ttl
 
     @property
-    def ttl(self):
+    def ttl(self) -> int:
         return self._ttl
 
-    def set_retry_timeout(self, retry_timeout):
+    def set_retry_timeout(self, retry_timeout: int) -> None:
         self._sync_obj.set_retry_timeout(retry_timeout)
 
-    def reload_config(self, config):
+    def reload_config(self, config: Union['Config', Dict[str, Any]]) -> None:
         super(Raft, self).reload_config(config)
         globalDnsResolver().setTimeouts(self.ttl, self.loop_wait)
 
     @staticmethod
-    def member(key, value):
+    def member(key: str, value: Dict[str, Any]) -> Member:
         return Member.from_node(value['index'], os.path.basename(key), None, value['value'])
 
-    def _cluster_from_nodes(self, nodes):
+    def _cluster_from_nodes(self, nodes: Dict[str, Any]) -> Cluster:
         # get initialize flag
         initialize = nodes.get(self._INITIALIZE)
         initialize = initialize and initialize['value']
@@ -348,7 +357,7 @@ class Raft(AbstractDCS):
             slots = None
 
         try:
-            last_lsn = int(last_lsn)
+            last_lsn = int(last_lsn or '')
         except Exception:
             last_lsn = 0
 
@@ -380,80 +389,86 @@ class Raft(AbstractDCS):
 
         return Cluster(initialize, config, leader, last_lsn, members, failover, sync, history, slots, failsafe)
 
-    def _cluster_loader(self, path):
+    def _cluster_loader(self, path: str) -> Cluster:
         response = self._sync_obj.get(path, recursive=True)
         if not response:
             return Cluster.empty()
         nodes = {key[len(path):]: value for key, value in response.items()}
         return self._cluster_from_nodes(nodes)
 
-    def _citus_cluster_loader(self, path):
-        clusters = defaultdict(dict)
+    def _citus_cluster_loader(self, path: str) -> Dict[int, Cluster]:
+        clusters: Dict[int, Dict[str, Any]] = defaultdict(dict)
         response = self._sync_obj.get(path, recursive=True)
-        for key, value in response.items():
+        for key, value in (response or {}).items():
             key = key[len(path):].split('/', 1)
             if len(key) == 2 and citus_group_re.match(key[0]):
                 clusters[int(key[0])][key[1]] = value
         return {group: self._cluster_from_nodes(nodes) for group, nodes in clusters.items()}
 
-    def _load_cluster(self, path, loader):
+    def _load_cluster(
+            self, path: str, loader: Callable[[str], Union[Cluster, Dict[int, Cluster]]]
+    ) -> Union[Cluster, Dict[int, Cluster]]:
         return loader(path)
 
-    def _write_leader_optime(self, last_lsn):
-        return self._sync_obj.set(self.leader_optime_path, last_lsn, timeout=1)
+    def _write_leader_optime(self, last_lsn: str) -> bool:
+        return self._sync_obj.set(self.leader_optime_path, last_lsn, timeout=1) is not False
 
-    def _write_status(self, value):
-        return self._sync_obj.set(self.status_path, value, timeout=1)
+    def _write_status(self, value: str) -> bool:
+        return self._sync_obj.set(self.status_path, value, timeout=1) is not False
 
-    def _write_failsafe(self, value):
-        return self._sync_obj.set(self.failsafe_path, value, timeout=1)
+    def _write_failsafe(self, value: str) -> bool:
+        return self._sync_obj.set(self.failsafe_path, value, timeout=1) is not False
 
-    def _update_leader(self):
+    def _update_leader(self, leader: Leader) -> bool:
         ret = self._sync_obj.set(self.leader_path, self._name, ttl=self._ttl,
-                                 handle_raft_error=False, prevValue=self._name)
+                                 handle_raft_error=False, prevValue=self._name) is not False
         if not ret and self._sync_obj.get(self.leader_path) is None:
             ret = self.attempt_to_acquire_leader()
         return ret
 
-    def attempt_to_acquire_leader(self):
-        return self._sync_obj.set(self.leader_path, self._name, ttl=self._ttl, handle_raft_error=False, prevExist=False)
+    def attempt_to_acquire_leader(self) -> bool:
+        return self._sync_obj.set(self.leader_path, self._name, ttl=self._ttl,
+                                  handle_raft_error=False, prevExist=False) is not False
 
-    def set_failover_value(self, value, index=None):
-        return self._sync_obj.set(self.failover_path, value, prevIndex=index)
+    def set_failover_value(self, value: str, version: Optional[int] = None) -> bool:
+        return self._sync_obj.set(self.failover_path, value, prevIndex=version) is not False
 
-    def set_config_value(self, value, index=None):
-        return self._sync_obj.set(self.config_path, value, prevIndex=index)
+    def set_config_value(self, value: str, version: Optional[int] = None) -> bool:
+        return self._sync_obj.set(self.config_path, value, prevIndex=version) is not False
 
-    def touch_member(self, data):
-        data = json.dumps(data, separators=(',', ':'))
-        return self._sync_obj.set(self.member_path, data, self._ttl, timeout=2)
+    def touch_member(self, data: Dict[str, Any]) -> bool:
+        value = json.dumps(data, separators=(',', ':'))
+        return self._sync_obj.set(self.member_path, value, self._ttl, timeout=2) is not False
 
-    def take_leader(self):
-        return self._sync_obj.set(self.leader_path, self._name, ttl=self._ttl)
+    def take_leader(self) -> bool:
+        return self._sync_obj.set(self.leader_path, self._name, ttl=self._ttl) is not False
 
-    def initialize(self, create_new=True, sysid=''):
-        return self._sync_obj.set(self.initialize_path, sysid, prevExist=(not create_new))
+    def initialize(self, create_new: bool = True, sysid: str = '') -> bool:
+        return self._sync_obj.set(self.initialize_path, sysid, prevExist=(not create_new)) is not False
 
-    def _delete_leader(self):
+    def _delete_leader(self) -> bool:
         return self._sync_obj.delete(self.leader_path, prevValue=self._name, timeout=1)
 
-    def cancel_initialization(self):
+    def cancel_initialization(self) -> bool:
         return self._sync_obj.delete(self.initialize_path)
 
-    def delete_cluster(self):
+    def delete_cluster(self) -> bool:
         return self._sync_obj.delete(self.client_path(''), recursive=True)
 
-    def set_history_value(self, value):
-        return self._sync_obj.set(self.history_path, value)
+    def set_history_value(self, value: str) -> bool:
+        return self._sync_obj.set(self.history_path, value) is not False
 
-    def set_sync_state_value(self, value, index=None):
-        return self._sync_obj.set(self.sync_path, value, prevIndex=index)
+    def set_sync_state_value(self, value: str, version: Optional[int] = None) -> Union[int, bool]:
+        ret = self._sync_obj.set(self.sync_path, value, prevIndex=version)
+        if isinstance(ret, dict):
+            return ret['index']
+        return ret
 
-    def delete_sync_state(self, index=None):
-        return self._sync_obj.delete(self.sync_path, prevIndex=index)
+    def delete_sync_state(self, version: Optional[int] = None) -> bool:
+        return self._sync_obj.delete(self.sync_path, prevIndex=version)
 
-    def watch(self, leader_index, timeout):
+    def watch(self, leader_version: Optional[int], timeout: float) -> bool:
         try:
-            return super(Raft, self).watch(leader_index, timeout)
+            return super(Raft, self).watch(leader_version, timeout)
         finally:
             self.event.clear()

patroni/dcs/zookeeper.py

@@ -1,18 +1,22 @@
 import json
 import logging
 import select
+import socket
 import time
 
 from kazoo.client import KazooClient, KazooState, KazooRetry
 from kazoo.exceptions import ConnectionClosedError, NoNodeError, NodeExistsError, SessionExpiredError
-from kazoo.handlers.threading import SequentialThreadingHandler
-from kazoo.protocol.states import KeeperState
+from kazoo.handlers.threading import AsyncResult, SequentialThreadingHandler
+from kazoo.protocol.states import KeeperState, WatchedEvent, ZnodeStat
 from kazoo.retry import RetryFailedError
-from kazoo.security import make_acl
+from kazoo.security import ACL, make_acl
+from typing import Any, Callable, Dict, List, Optional, Union, Tuple, TYPE_CHECKING
 
 from . import AbstractDCS, ClusterConfig, Cluster, Failover, Leader, Member, SyncState, TimelineHistory, citus_group_re
 from ..exceptions import DCSError
 from ..utils import deep_compare
+if TYPE_CHECKING:  # pragma: no cover
+    from ..config import Config
 
 logger = logging.getLogger(__name__)
 
@@ -23,14 +27,14 @@ class ZooKeeperError(DCSError):
 
 class PatroniSequentialThreadingHandler(SequentialThreadingHandler):
 
-    def __init__(self, connect_timeout):
+    def __init__(self, connect_timeout: Union[int, float]) -> None:
         super(PatroniSequentialThreadingHandler, self).__init__()
         self.set_connect_timeout(connect_timeout)
 
-    def set_connect_timeout(self, connect_timeout):
-        self._connect_timeout = max(1.0, connect_timeout/2.0)  # try to connect to zookeeper node during loop_wait/2
+    def set_connect_timeout(self, connect_timeout: Union[int, float]) -> None:
+        self._connect_timeout = max(1.0, connect_timeout / 2.0)  # try to connect to zookeeper node during loop_wait/2
 
-    def create_connection(self, *args, **kwargs):
+    def create_connection(self, *args: Any, **kwargs: Any) -> socket.socket:
         """This method is trying to establish connection with one of the zookeeper nodes.
            Somehow strategy "fail earlier and retry more often" works way better comparing to
            the original strategy "try to connect with specified timeout".
@@ -41,16 +45,16 @@ class PatroniSequentialThreadingHandler(SequentialThreadingHandler):
         :param args: always contains `tuple(host, port)` as the first element and could contain
                      `connect_timeout` (negotiated session timeout) as the second element."""
 
-        args = list(args)
-        if len(args) == 0:  # kazoo 2.6.0 slightly changed the way how it calls create_connection method
-            kwargs['timeout'] = max(self._connect_timeout, kwargs.get('timeout', self._connect_timeout*10)/10.0)
-        elif len(args) == 1:
-            args.append(self._connect_timeout)
+        args_list: List[Any] = list(args)
+        if len(args_list) == 0:  # kazoo 2.6.0 slightly changed the way how it calls create_connection method
+            kwargs['timeout'] = max(self._connect_timeout, kwargs.get('timeout', self._connect_timeout * 10) / 10.0)
+        elif len(args_list) == 1:
+            args_list.append(self._connect_timeout)
         else:
-            args[1] = max(self._connect_timeout, args[1]/10.0)
-        return super(PatroniSequentialThreadingHandler, self).create_connection(*args, **kwargs)
+            args_list[1] = max(self._connect_timeout, args_list[1] / 10.0)
+        return super(PatroniSequentialThreadingHandler, self).create_connection(*args_list, **kwargs)
 
-    def select(self, *args, **kwargs):
+    def select(self, *args: Any, **kwargs: Any) -> Any:
         """
         Python 3.XY may raise following exceptions if select/poll are called with an invalid socket:
         - `ValueError`: because fd == -1
@@ -68,7 +72,7 @@ class PatroniSequentialThreadingHandler(SequentialThreadingHandler):
 
 class PatroniKazooClient(KazooClient):
 
-    def _call(self, request, async_object):
+    def _call(self, request: Tuple[Any], async_object: AsyncResult) -> Optional[bool]:
         # Before kazoo==2.7.0 it wasn't possible to send requests to zookeeper if
         # the connection is in the SUSPENDED state and Patroni was strongly relying on it.
         # The https://github.com/python-zk/kazoo/pull/588 changed it, and now such requests are queued.
@@ -82,10 +86,10 @@ class PatroniKazooClient(KazooClient):
 
 class ZooKeeper(AbstractDCS):
 
-    def __init__(self, config):
+    def __init__(self, config: Dict[str, Any]) -> None:
         super(ZooKeeper, self).__init__(config)
 
-        hosts = config.get('hosts', [])
+        hosts: Union[str, List[str]] = config.get('hosts', [])
         if isinstance(hosts, list):
             hosts = ','.join(hosts)
 
@@ -94,17 +98,18 @@ class ZooKeeper(AbstractDCS):
         kwargs = {v: config[k] for k, v in mapping.items() if k in config}
 
         if 'set_acls' in config:
-            kwargs['default_acl'] = []
+            default_acl: List[ACL] = []
             for principal, permissions in config['set_acls'].items():
                 normalizedPermissions = [p.upper() for p in permissions]
-                kwargs['default_acl'].append(make_acl(scheme='x509',
-                                                      credential=principal,
-                                                      read='READ' in normalizedPermissions,
-                                                      write='WRITE' in normalizedPermissions,
-                                                      create='CREATE' in normalizedPermissions,
-                                                      delete='DELETE' in normalizedPermissions,
-                                                      admin='ADMIN' in normalizedPermissions,
-                                                      all='ALL' in normalizedPermissions))
+                default_acl.append(make_acl(scheme='x509',
+                                            credential=principal,
+                                            read='READ' in normalizedPermissions,
+                                            write='WRITE' in normalizedPermissions,
+                                            create='CREATE' in normalizedPermissions,
+                                            delete='DELETE' in normalizedPermissions,
+                                            admin='ADMIN' in normalizedPermissions,
+                                            all='ALL' in normalizedPermissions))
+            kwargs['default_acl'] = default_acl
 
         self._client = PatroniKazooClient(hosts, handler=PatroniSequentialThreadingHandler(config['retry_timeout']),
                                           timeout=config['ttl'], connection_retry=KazooRetry(max_delay=1, max_tries=-1,
@@ -112,16 +117,16 @@ class ZooKeeper(AbstractDCS):
                                           deadline=config['retry_timeout'], sleep_func=time.sleep), **kwargs)
         self._client.add_listener(self.session_listener)
 
-        self._fetch_cluster = True
-        self._fetch_status = True
-        self.__last_member_data = None
+        self._fetch_cluster: bool = True
+        self._fetch_status: bool = True
+        self.__last_member_data: Optional[Dict[str, Any]] = None
 
         self._orig_kazoo_connect = self._client._connection._connect
         self._client._connection._connect = self._kazoo_connect
 
         self._client.start()
 
-    def _kazoo_connect(self, *args):
+    def _kazoo_connect(self, *args: Any) -> Tuple[Union[int, float], Union[int, float]]:
         """Kazoo is using Ping's to determine health of connection to zookeeper. If there is no
         response on Ping after Ping interval (1/2 from read_timeout) it will consider current
         connection dead and try to connect to another node. Without this "magic" it was taking
@@ -134,32 +139,30 @@ class ZooKeeper(AbstractDCS):
         `write_leader_optime()` methods, which also may hang..."""
 
         ret = self._orig_kazoo_connect(*args)
-        return max(self.loop_wait - 2, 2)*1000, ret[1]
+        return max(self.loop_wait - 2, 2) * 1000, ret[1]
 
-    def session_listener(self, state):
+    def session_listener(self, state: str) -> None:
         if state in [KazooState.SUSPENDED, KazooState.LOST]:
             self.cluster_watcher(None)
 
-    def status_watcher(self, event):
+    def status_watcher(self, event: Optional[WatchedEvent]) -> None:
         self._fetch_status = True
         self.event.set()
 
-    def cluster_watcher(self, event):
+    def cluster_watcher(self, event: Optional[WatchedEvent]) -> None:
         self._fetch_cluster = True
         if not event or event.state != KazooState.CONNECTED or event.path.startswith(self.client_path('')):
             self.status_watcher(event)
 
-    def members_watcher(self, event):
-        self._fetch_cluster = True
-
-    def reload_config(self, config):
+    def reload_config(self, config: Union['Config', Dict[str, Any]]) -> None:
         self.set_retry_timeout(config['retry_timeout'])
 
         loop_wait = config['loop_wait']
 
         loop_wait_changed = self._loop_wait != loop_wait
         self._loop_wait = loop_wait
-        self._client.handler.set_connect_timeout(loop_wait)
+        if isinstance(self._client.handler, PatroniSequentialThreadingHandler):
+            self._client.handler.set_connect_timeout(loop_wait)
 
         # We need to reestablish connection to zookeeper if we want to change
         # read_timeout (and Ping interval respectively), because read_timeout
@@ -170,7 +173,7 @@ class ZooKeeper(AbstractDCS):
         if not self.set_ttl(config['ttl']) and loop_wait_changed:
             self._client._connection._socket.close()
 
-    def set_ttl(self, ttl):
+    def set_ttl(self, ttl: int) -> Optional[bool]:
         """It is not possible to change ttl (session_timeout) in zookeeper without
         destroying old session and creating the new one. This method returns `!True`
         if session_timeout has been changed (`restart()` has been called)."""
@@ -181,21 +184,23 @@ class ZooKeeper(AbstractDCS):
             return True
 
     @property
-    def ttl(self):
-        return self._client._session_timeout / 1000.0
+    def ttl(self) -> int:
+        return int(self._client._session_timeout / 1000.0)
 
-    def set_retry_timeout(self, retry_timeout):
+    def set_retry_timeout(self, retry_timeout: int) -> None:
         retry = self._client.retry if isinstance(self._client.retry, KazooRetry) else self._client._retry
         retry.deadline = retry_timeout
 
-    def get_node(self, key, watch=None):
+    def get_node(
+            self, key: str, watch: Optional[Callable[[WatchedEvent], None]] = None
+    ) -> Optional[Tuple[str, ZnodeStat]]:
         try:
             ret = self._client.get(key, watch)
             return (ret[0].decode('utf-8'), ret[1])
         except NoNodeError:
             return None
 
-    def get_status(self, path, leader):
+    def get_status(self, path: str, leader: Optional[Leader]) -> Tuple[int, Optional[Dict[str, int]]]:
         watch = self.status_watcher if not leader or leader.name != self._name else None
 
         status = self.get_node(path + self._STATUS, watch)
@@ -212,7 +217,7 @@ class ZooKeeper(AbstractDCS):
             slots = None
 
         try:
-            last_lsn = int(last_lsn)
+            last_lsn = int(last_lsn or '')
         except Exception:
             last_lsn = 0
 
@@ -220,24 +225,24 @@ class ZooKeeper(AbstractDCS):
         return last_lsn, slots
 
     @staticmethod
-    def member(name, value, znode):
+    def member(name: str, value: str, znode: ZnodeStat) -> Member:
         return Member.from_node(znode.version, name, znode.ephemeralOwner, value)
 
-    def get_children(self, key, watch=None):
+    def get_children(self, key: str, watch: Optional[Callable[[WatchedEvent], None]] = None) -> List[str]:
         try:
             return self._client.get_children(key, watch)
         except NoNodeError:
             return []
 
-    def load_members(self, path):
-        members = []
+    def load_members(self, path: str) -> List[Member]:
+        members: List[Member] = []
         for member in self.get_children(path + self._MEMBERS, self.cluster_watcher):
             data = self.get_node(path + self._MEMBERS + member)
             if data is not None:
                 members.append(self.member(member, *data))
         return members
 
-    def _cluster_loader(self, path):
+    def _cluster_loader(self, path: str) -> Cluster:
         self._fetch_cluster = False
         self.event.clear()
         nodes = set(self.get_children(path, self.cluster_watcher))
@@ -268,7 +273,7 @@ class ZooKeeper(AbstractDCS):
             member = Member(-1, leader[0], None, {})
             member = ([m for m in members if m.name == leader[0]] or [member])[0]
             leader = Leader(leader[1].version, leader[1].ephemeralOwner, member)
-            self._fetch_cluster = member.index == -1
+            self._fetch_cluster = member.version == -1
 
         # get last known leader lsn and slots
         last_lsn, slots = self.get_status(path, leader)
@@ -286,9 +291,9 @@ class ZooKeeper(AbstractDCS):
 
         return Cluster(initialize, config, leader, last_lsn, members, failover, sync, history, slots, failsafe)
 
-    def _citus_cluster_loader(self, path):
+    def _citus_cluster_loader(self, path: str) -> Dict[int, Cluster]:
         fetch_cluster = False
-        ret = {}
+        ret: Dict[int, Cluster] = {}
         for node in self.get_children(path, self.cluster_watcher):
             if citus_group_re.match(node):
                 ret[int(node)] = self._cluster_loader(path + node + '/')
@@ -296,7 +301,9 @@ class ZooKeeper(AbstractDCS):
         self._fetch_cluster = fetch_cluster
         return ret
 
-    def _load_cluster(self, path, loader):
+    def _load_cluster(
+            self, path: str, loader: Callable[[str], Union[Cluster, Dict[int, Cluster]]]
+    ) -> Union[Cluster, Dict[int, Cluster]]:
         cluster = self.cluster if path == self._base_path + '/' else None
         if self._fetch_cluster or cluster is None:
             try:
@@ -315,18 +322,18 @@ class ZooKeeper(AbstractDCS):
                 try:
                     last_lsn, slots = self.get_status(self.client_path(''), cluster.leader)
                     self.event.clear()
-                    cluster = list(cluster)
-                    cluster[3] = last_lsn
-                    cluster[8] = slots
-                    cluster = Cluster(*cluster)
+                    new_cluster: List[Any] = list(cluster)
+                    new_cluster[3] = last_lsn
+                    new_cluster[8] = slots
+                    cluster = Cluster(*new_cluster)
                 except Exception:
                     pass
         return cluster
 
-    def _bypass_caches(self):
+    def _bypass_caches(self) -> None:
         self._fetch_cluster = True
 
-    def _create(self, path, value, retry=False, ephemeral=False):
+    def _create(self, path: str, value: bytes, retry: bool = False, ephemeral: bool = False) -> bool:
         try:
             if retry:
                 self._client.retry(self._client.create, path, value, makepath=True, ephemeral=ephemeral)
@@ -337,7 +344,7 @@ class ZooKeeper(AbstractDCS):
             logger.exception('Failed to create %s', path)
         return False
 
-    def attempt_to_acquire_leader(self):
+    def attempt_to_acquire_leader(self) -> bool:
         try:
             self._client.retry(self._client.create, self.leader_path, self._name.encode('utf-8'),
                                makepath=True, ephemeral=True)
@@ -350,57 +357,67 @@ class ZooKeeper(AbstractDCS):
         logger.info('Could not take out TTL lock')
         return False
 
-    def _set_or_create(self, key, value, index=None, retry=False, do_not_create_empty=False):
-        value = value.encode('utf-8')
+    def _set_or_create(self, key: str, value: str, version: Optional[int] = None,
+                       retry: bool = False, do_not_create_empty: bool = False) -> Union[int, bool]:
+        value_bytes = value.encode('utf-8')
         try:
             if retry:
-                self._client.retry(self._client.set, key, value, version=index or -1)
+                ret = self._client.retry(self._client.set, key, value_bytes, version=version or -1)
             else:
-                self._client.set_async(key, value, version=index or -1).get(timeout=1)
-            return True
+                ret = self._client.set_async(key, value_bytes, version=version or -1).get(timeout=1)
+            return ret.version
         except NoNodeError:
-            if do_not_create_empty and not value:
+            if do_not_create_empty and not value_bytes:
                 return True
-            elif index is None:
-                return self._create(key, value, retry)
+            elif version is None:
+                if self._create(key, value_bytes, retry):
+                    return 0
             else:
                 return False
         except Exception:
             logger.exception('Failed to update %s', key)
         return False
 
-    def set_failover_value(self, value, index=None):
-        return self._set_or_create(self.failover_path, value, index)
+    def set_failover_value(self, value: str, version: Optional[int] = None) -> bool:
+        return self._set_or_create(self.failover_path, value, version) is not False
 
-    def set_config_value(self, value, index=None):
-        return self._set_or_create(self.config_path, value, index, retry=True)
+    def set_config_value(self, value: str, version: Optional[int] = None) -> bool:
+        return self._set_or_create(self.config_path, value, version, retry=True) is not False
 
-    def initialize(self, create_new=True, sysid=""):
-        sysid = sysid.encode('utf-8')
-        return self._create(self.initialize_path, sysid, retry=True) if create_new \
-            else self._client.retry(self._client.set, self.initialize_path, sysid)
+    def initialize(self, create_new: bool = True, sysid: str = "") -> bool:
+        sysid_bytes = sysid.encode('utf-8')
+        return self._create(self.initialize_path, sysid_bytes, retry=True) if create_new \
+            else self._client.retry(self._client.set, self.initialize_path, sysid_bytes)
 
-    def touch_member(self, data):
+    def touch_member(self, data: Dict[str, Any]) -> bool:
         cluster = self.cluster
         member = cluster and cluster.get_member(self._name, fallback_to_leader=False)
         member_data = self.__last_member_data or member and member.data
-        #  We want to notify leader if some important fields in the member key changed by removing ZNode
-        if member and (self._client.client_id is not None and member.session != self._client.client_id[0] or
-                       not (deep_compare(member_data.get('tags', {}), data.get('tags', {})) and
-                            (member_data.get('state') == data.get('state') or
-                                'running' not in (member_data.get('state'), data.get('state'))) and
-                            member_data.get('version') == data.get('version') and
-                            member_data.get('checkpoint_after_promote') == data.get('checkpoint_after_promote'))):
-            try:
-                self._client.delete_async(self.member_path).get(timeout=1)
-            except NoNodeError:
-                pass
-            except Exception:
-                return False
-            member = None
+        if member and member_data:
+            is_leader = data.get('role') in ('master', 'primary', 'standby_leader')
+            checkpoint_after_promote_changed = member_data.get('checkpoint_after_promote') \
+                != data.get('checkpoint_after_promote')
+            state_running_changed = member_data.get('state') != data.get('state') \
+                and 'running' in (member_data.get('state'), data.get('state'))
+            tags_changed = not deep_compare(member_data.get('tags', {}), data.get('tags', {}))
+
+            # We want delete the member ZNode if:
+            # - our session doesn't match with session id on our member key; or
+            # - we want to notify leader if some important fields in the member key changed; or
+            # - if we are the leader and want to notify replicas about checkpoint_after_promote;
+            if self._client.client_id is not None and member.session != self._client.client_id[0] \
+                    or is_leader and checkpoint_after_promote_changed \
+                    or not is_leader and (state_running_changed or tags_changed):
+                try:
+                    self._client.delete_async(self.member_path).get(timeout=1)
+                except NoNodeError:
+                    pass
+                except Exception:
+                    return False
+                member = None
 
         encoded_data = json.dumps(data, separators=(',', ':')).encode('utf-8')
-        if member:
+        if member and member_data:
             if deep_compare(data, member_data):
                 return True
         else:
@@ -421,22 +438,20 @@ class ZooKeeper(AbstractDCS):
 
         return False
 
-    def take_leader(self):
+    def take_leader(self) -> bool:
         return self.attempt_to_acquire_leader()
 
-    def _write_leader_optime(self, last_lsn):
-        return self._set_or_create(self.leader_optime_path, last_lsn)
+    def _write_leader_optime(self, last_lsn: str) -> bool:
+        return self._set_or_create(self.leader_optime_path, last_lsn) is not False
 
-    def _write_status(self, value):
-        return self._set_or_create(self.status_path, value)
+    def _write_status(self, value: str) -> bool:
+        return self._set_or_create(self.status_path, value) is not False
 
-    def _write_failsafe(self, value):
-        return self._set_or_create(self.failsafe_path, value)
+    def _write_failsafe(self, value: str) -> bool:
+        return self._set_or_create(self.failsafe_path, value) is not False
 
-    def _update_leader(self):
-        cluster = self.cluster
-        session = cluster and isinstance(cluster.leader, Leader) and cluster.leader.session
-        if self._client.client_id and self._client.client_id[0] != session:
+    def _update_leader(self, leader: Leader) -> bool:
+        if self._client.client_id and self._client.client_id[0] != leader.session:
             logger.warning('Recreating the leader ZNode due to ownership mismatch')
             try:
                 self._client.retry(self._client.delete, self.leader_path)
@@ -458,38 +473,40 @@ class ZooKeeper(AbstractDCS):
                 return False
         return True
 
-    def _delete_leader(self):
+    def _delete_leader(self) -> bool:
         self._client.restart()
         return True
 
-    def _cancel_initialization(self):
+    def _cancel_initialization(self) -> None:
         node = self.get_node(self.initialize_path)
         if node:
             self._client.delete(self.initialize_path, version=node[1].version)
 
-    def cancel_initialization(self):
+    def cancel_initialization(self) -> bool:
         try:
             self._client.retry(self._cancel_initialization)
+            return True
         except Exception:
             logger.exception("Unable to delete initialize key")
+        return False
 
-    def delete_cluster(self):
+    def delete_cluster(self) -> bool:
         try:
             return self._client.retry(self._client.delete, self.client_path(''), recursive=True)
         except NoNodeError:
             return True
 
-    def set_history_value(self, value):
-        return self._set_or_create(self.history_path, value)
+    def set_history_value(self, value: str) -> bool:
+        return self._set_or_create(self.history_path, value) is not False
 
-    def set_sync_state_value(self, value, index=None):
-        return self._set_or_create(self.sync_path, value, index, retry=True, do_not_create_empty=True)
+    def set_sync_state_value(self, value: str, version: Optional[int] = None) -> Union[int, bool]:
+        return self._set_or_create(self.sync_path, value, version, retry=True, do_not_create_empty=True)
 
-    def delete_sync_state(self, index=None):
-        return self.set_sync_state_value("{}", index)
+    def delete_sync_state(self, version: Optional[int] = None) -> bool:
+        return self.set_sync_state_value("{}", version) is not False
 
-    def watch(self, leader_index, timeout):
-        ret = super(ZooKeeper, self).watch(leader_index, timeout + 0.5)
+    def watch(self, leader_version: Optional[int], timeout: float) -> bool:
+        ret = super(ZooKeeper, self).watch(leader_version, timeout + 0.5)
         if ret and not self._fetch_status:
             self._fetch_cluster = True
         return ret or self._fetch_cluster

patroni/exceptions.py

@@ -1,37 +1,55 @@
+"""Implement high-level Patroni exceptions.
+
+More specific exceptions can be found in other modules, as subclasses of any exception defined in this module.
+"""
+from typing import Any
+
+
 class PatroniException(Exception):
+    """Parent class for all kind of Patroni exceptions.
 
-    """Parent class for all kind of exceptions related to selected distributed configuration store"""
+    :ivar value: description of the exception.
+    """
 
-    def __init__(self, value):
+    def __init__(self, value: Any) -> None:
+        """Create a new instance of :class:`PatroniException` with the given description.
+
+        :param value: description of the exception.
+        """
         self.value = value
 
-    def __str__(self):
-        """
-        >>> str(PatroniException('foo'))
-        "'foo'"
-        """
-        return repr(self.value)
-
 
 class PatroniFatalException(PatroniException):
+    """Catastrophic exception that prevents Patroni from performing its job."""
+
     pass
 
 
 class PostgresException(PatroniException):
+    """Any exception related with Postgres management."""
+
     pass
 
 
 class DCSError(PatroniException):
+    """Parent class for all kind of DCS related exceptions."""
+
     pass
 
 
 class PostgresConnectionException(PostgresException):
+    """Any problem faced while connecting to a Postgres instance."""
+
     pass
 
 
 class WatchdogError(PatroniException):
+    """Any problem faced while managing a watchdog device."""
+
     pass
 
 
 class ConfigParseError(PatroniException):
+    """Any issue identified while loading or validating the Patroni configuration."""
+
     pass

patroni/file_perm.py

@@ -0,0 +1,95 @@
+"""Helper object that helps with figuring out file and directory permissions based on permissions of PGDATA.
+
+:var logger: logger of this module.
+:var pg_perm: instance of the :class:`__FilePermissions` object.
+"""
+import logging
+import os
+import stat
+
+logger = logging.getLogger(__name__)
+
+
+class __FilePermissions:
+    """Helper class for managing permissions of directories and files under PGDATA.
+
+    Execute :meth:`set_permissions_from_data_directory` to figure out which permissions should be used for files and
+    directories under PGDATA based on permissions of PGDATA root directory.
+    """
+
+    # Mode mask for data directory permissions that only allows the owner to
+    # read/write directories and files -- mask 077.
+    __PG_MODE_MASK_OWNER = stat.S_IRWXG | stat.S_IRWXO
+
+    # Mode mask for data directory permissions that also allows group read/execute -- mask 027.
+    __PG_MODE_MASK_GROUP = stat.S_IWGRP | stat.S_IRWXO
+
+    # Default mode for creating directories -- mode 700.
+    __PG_DIR_MODE_OWNER = stat.S_IRWXU
+
+    # Mode for creating directories that allows group read/execute -- mode 750.
+    __PG_DIR_MODE_GROUP = stat.S_IRWXU | stat.S_IRGRP | stat.S_IXGRP
+
+    # Default mode for creating files -- mode 600.
+    __PG_FILE_MODE_OWNER = stat.S_IRUSR | stat.S_IWUSR
+
+    # Mode for creating files that allows group read -- mode 640.
+    __PG_FILE_MODE_GROUP = stat.S_IRUSR | stat.S_IWUSR | stat.S_IRGRP
+
+    def __init__(self) -> None:
+        """Create a :class:`__FilePermissions` object and set default permissions."""
+        self.__set_owner_permissions()
+        self.__set_umask()
+
+    def __set_umask(self) -> None:
+        """Set umask value based on calculations.
+
+        .. note::
+            Should only be called once either :meth:`__set_owner_permissions`
+            or :meth:`__set_group_permissions` has been executed.
+        """
+        try:
+            os.umask(self.__pg_mode_mask)
+        except Exception as e:
+            logger.error('Can not set umask to %03o: %r', self.__pg_mode_mask, e)
+
+    def __set_owner_permissions(self) -> None:
+        """Make directories/files accessible only by the owner."""
+        self.__pg_dir_create_mode = self.__PG_DIR_MODE_OWNER
+        self.__pg_file_create_mode = self.__PG_FILE_MODE_OWNER
+        self.__pg_mode_mask = self.__PG_MODE_MASK_OWNER
+
+    def __set_group_permissions(self) -> None:
+        """Make directories/files accessible by the owner and readable by group."""
+        self.__pg_dir_create_mode = self.__PG_DIR_MODE_GROUP
+        self.__pg_file_create_mode = self.__PG_FILE_MODE_GROUP
+        self.__pg_mode_mask = self.__PG_MODE_MASK_GROUP
+
+    def set_permissions_from_data_directory(self, data_dir: str) -> None:
+        """Set new permissions based on provided *data_dir*.
+
+        :param data_dir: reference to PGDATA to calculate permissions from.
+        """
+        try:
+            st = os.stat(data_dir)
+            if (st.st_mode & self.__PG_DIR_MODE_GROUP) == self.__PG_DIR_MODE_GROUP:
+                self.__set_group_permissions()
+            else:
+                self.__set_owner_permissions()
+        except Exception as e:
+            logger.error('Can not check permissions on %s: %r', data_dir, e)
+        else:
+            self.__set_umask()
+
+    @property
+    def dir_create_mode(self) -> int:
+        """Directory permissions."""
+        return self.__pg_dir_create_mode
+
+    @property
+    def file_create_mode(self) -> int:
+        """File permissions."""
+        return self.__pg_file_create_mode
+
+
+pg_perm = __FilePermissions()

patroni/log.py

@@ -1,3 +1,8 @@
+"""Patroni logging facilities.
+
+Daemon processes will use a 2-step logging handler. Whenever a log message is issued it is initially enqueued in-memory
+and is later asynchronously flushed by a thread to the final destination.
+"""
 import logging
 import os
 import sys
@@ -8,38 +13,81 @@ from patroni.utils import deep_compare
 from queue import Queue, Full
 from threading import Lock, Thread
 
+from typing import Any, Dict, List, Optional, Union, TYPE_CHECKING
+
 _LOGGER = logging.getLogger(__name__)
 
 
-def debug_exception(logger_obj, msg, *args, **kwargs):
+def debug_exception(self: logging.Logger, msg: object, *args: Any, **kwargs: Any) -> None:
+    """Add full stack trace info to debug log messages and partial to others.
+
+    Handle :func:`~self.exception` calls for *self*.
+
+    .. note::
+        * If *self* log level is set to ``DEBUG``, then issue a ``DEBUG`` message with the complete stack trace;
+        * If *self* log level is ``INFO`` or higher, then issue an ``ERROR`` message with only the last line of
+            the stack trace.
+
+    :param self: logger for which :func:`~self.exception` will be processed.
+    :param msg: the message related to the exception to be logged.
+    :param args: positional arguments to be passed to :func:`~self.debug` or :func:`~self.error`.
+    :param kwargs: keyword arguments to be passed to :func:`~self.debug` or :func:`~self.error`.
+    """
     kwargs.pop("exc_info", False)
-    if logger_obj.isEnabledFor(logging.DEBUG):
-        logger_obj.debug(msg, *args, exc_info=True, **kwargs)
+    if self.isEnabledFor(logging.DEBUG):
+        self.debug(msg, *args, exc_info=True, **kwargs)
     else:
         msg = "{0}, DETAIL: '{1}'".format(msg, sys.exc_info()[1])
-        logger_obj.error(msg, *args, exc_info=False, **kwargs)
+        self.error(msg, *args, exc_info=False, **kwargs)
 
 
-def error_exception(logger_obj, msg, *args, **kwargs):
+def error_exception(self: logging.Logger, msg: object, *args: Any, **kwargs: Any) -> None:
+    """Add full stack trace info to error messages.
+
+    Handle :func:`~self.exception` calls for *self*.
+
+    .. note::
+        * By default issue an ``ERROR`` message with the complete stack trace. If you do not want to show the complete
+          stack trace, call with ``exc_info=False``.
+
+    :param self: logger for which :func:`~self.exception` will be processed.
+    :param msg: the message related to the exception to be logged.
+    :param args: positional arguments to be passed to :func:`~self.error`.
+    :param kwargs: keyword arguments to be passed to :func:`~self.error`.
+    """
     exc_info = kwargs.pop("exc_info", True)
-    logger_obj.error(msg, *args, exc_info=exc_info, **kwargs)
+    self.error(msg, *args, exc_info=exc_info, **kwargs)
 
 
 class QueueHandler(logging.Handler):
+    """Queue-based logging handler.
 
-    def __init__(self):
-        logging.Handler.__init__(self)
-        self.queue = Queue()
+    :ivar queue: queue to hold log messages that are pending to be flushed to the final destination.
+    """
+
+    def __init__(self) -> None:
+        """Queue initialised and initial records_lost established."""
+        super().__init__()
+        self.queue: Queue[Union[logging.LogRecord, None]] = Queue()
         self._records_lost = 0
 
-    def _put_record(self, record):
+    def _put_record(self, record: logging.LogRecord) -> None:
+        """Asynchronously enqueue a log record.
+
+        :param record: the record to be logged.
+        """
         self.format(record)
         record.msg = record.message
         record.args = None
         record.exc_info = None
         self.queue.put_nowait(record)
 
-    def _try_to_report_lost_records(self):
+    def _try_to_report_lost_records(self) -> None:
+        """Report the number of log messages that have been lost and reset the counter.
+
+        .. note::
+            It will issue an ``WARNING`` message in the logs with the number of lost log messages.
+        """
         if self._records_lost:
             try:
                 record = _LOGGER.makeRecord(_LOGGER.name, logging.WARNING, __file__, 0,
@@ -50,7 +98,15 @@ class QueueHandler(logging.Handler):
             except Exception:
                 pass
 
-    def emit(self, record):
+    def emit(self, record: logging.LogRecord) -> None:
+        """Handle each log record that is emitted.
+
+        Call :func:`_put_record` to enqueue the emitted log record.
+
+        Also check if we have previously lost any log record, and if so, log a ``WARNING`` message.
+
+        :param record: the record that was emitted.
+        """
         try:
             self._put_record(record)
             self._try_to_report_lost_records()
@@ -58,21 +114,60 @@ class QueueHandler(logging.Handler):
             self._records_lost += 1
 
     @property
-    def records_lost(self):
+    def records_lost(self) -> int:
+        """Number of log messages that have been lost while the queue was full."""
         return self._records_lost
 
 
 class ProxyHandler(logging.Handler):
+    """Handle log records in place of pending log handlers.
 
-    def __init__(self, patroni_logger):
-        logging.Handler.__init__(self)
+    .. note::
+        This is used to handle log messages while the logger thread has not started yet, in which case the queue-based
+        handler is not yet started.
+
+    :ivar patroni_logger: the logger thread.
+    """
+
+    def __init__(self, patroni_logger: 'PatroniLogger') -> None:
+        """Create a new :class:`ProxyHandler` instance.
+
+        :param patroni_logger: the logger thread.
+        """
+        super().__init__()
         self.patroni_logger = patroni_logger
 
-    def emit(self, record):
-        self.patroni_logger.log_handler.handle(record)
+    def emit(self, record: logging.LogRecord) -> None:
+        """Emit each log record that is handled.
+
+        Will push the log record down to :func:`~logging.Handler.handle` method of the currently configured log handler.
+
+        :param record: the record that was emitted.
+        """
+        if self.patroni_logger.log_handler is not None:
+            self.patroni_logger.log_handler.handle(record)
 
 
 class PatroniLogger(Thread):
+    """Logging thread for the Patroni daemon process.
+
+    It is a 2-step logging approach. Any time a log message is issued it is initially enqueued in-memory, and then
+    asynchronously flushed to the final destination by the logging thread.
+
+    .. seealso::
+        :class:`QueueHandler`: object used for enqueueing messages in-memory.
+
+    :cvar DEFAULT_LEVEL: default logging level (``INFO``).
+    :cvar DEFAULT_TRACEBACK_LEVEL: default traceback logging level (``ERROR``).
+    :cvar DEFAULT_FORMAT: default format of log messages (``%(asctime)s %(levelname)s: %(message)s``).
+    :cvar NORMAL_LOG_QUEUE_SIZE: expected number of log messages per HA loop when operating under a normal situation.
+    :cvar DEFAULT_MAX_QUEUE_SIZE: default maximum queue size for holding a backlog of log messages that are pending
+        to be flushed.
+    :cvar LOGGING_BROKEN_EXIT_CODE: exit code to be used if it detects(``5``).
+
+    :ivar log_handler: log handler that is currently being used by the thread.
+    :ivar log_handler_lock: lock used to modify ``log_handler``.
+    """
 
     DEFAULT_LEVEL = 'INFO'
     DEFAULT_TRACEBACK_LEVEL = 'ERROR'
@@ -82,14 +177,24 @@ class PatroniLogger(Thread):
     DEFAULT_MAX_QUEUE_SIZE = 1000
     LOGGING_BROKEN_EXIT_CODE = 5
 
-    def __init__(self):
+    def __init__(self) -> None:
+        """Prepare logging queue and proxy handlers as they become ready during daemon startup.
+
+        .. note::
+            While Patroni is starting up it keeps ``DEBUG`` log level, and writes log messages through a proxy handler.
+            Once the logger thread is finally started, it switches from that proxy handler to the queue based logger,
+            and applies the configured log settings. The switching is used to avoid that the logger thread prevents
+            Patroni from shutting down if any issue occurs in the meantime until the thread is properly started.
+        """
         super(PatroniLogger, self).__init__()
         self._queue_handler = QueueHandler()
         self._root_logger = logging.getLogger()
-        self._config = None
+        self._config: Optional[Dict[str, Any]] = None
         self.log_handler = None
         self.log_handler_lock = Lock()
-        self._old_handlers = []
+        self._old_handlers: List[logging.Handler] = []
+        # initially set log level to ``DEBUG`` while the logger thread has not started running yet. The daemon process
+        # will later adjust all log related settings with what was provided through the user configuration file.
         self.reload_config({'level': 'DEBUG'})
         # We will switch to the QueueHandler only when thread was started.
         # This is necessary to protect from the cases when Patroni constructor
@@ -97,26 +202,46 @@ class PatroniLogger(Thread):
         self._proxy_handler = ProxyHandler(self)
         self._root_logger.addHandler(self._proxy_handler)
 
-    def update_loggers(self):
-        loggers = deepcopy(self._config.get('loggers') or {})
+    def update_loggers(self) -> None:
+        """Configure loggers' log level as defined in ``log.loggers`` section of Patroni configuration.
+
+        .. note::
+            It creates logger objects that are not defined yet in the log manager.
+        """
+        loggers = deepcopy((self._config or {}).get('loggers') or {})
         for name, logger in self._root_logger.manager.loggerDict.items():
+            # ``Placeholder`` is a node in the log manager for which no logger has been defined. We are interested only
+            # in the ones that were defined
             if not isinstance(logger, logging.PlaceHolder):
+                # if this logger is present in ``log.loggers`` Patroni configuration, use the configured level,
+                # otherwise use ``logging.NOTSET``, which means it will inherit the level from any parent node up to
+                # the root for which log level is defined.
                 level = loggers.pop(name, logging.NOTSET)
                 logger.setLevel(level)
 
+        # define loggers that do not exist yet and set level as configured in ``log.loggers`` section of configuration.
         for name, level in loggers.items():
             logger = self._root_logger.manager.getLogger(name)
             logger.setLevel(level)
 
-    def reload_config(self, config):
+    def reload_config(self, config: Dict[str, Any]) -> None:
+        """Apply log related configuration.
+
+        .. note::
+            It is also able to deal with runtime configuration changes.
+
+        :param config: ``log`` section from Patroni configuration.
+        """
         if self._config is None or not deep_compare(self._config, config):
             with self._queue_handler.queue.mutex:
                 self._queue_handler.queue.maxsize = config.get('max_queue_size', self.DEFAULT_MAX_QUEUE_SIZE)
 
             self._root_logger.setLevel(config.get('level', PatroniLogger.DEFAULT_LEVEL))
             if config.get('traceback_level', PatroniLogger.DEFAULT_TRACEBACK_LEVEL).lower() == 'debug':
+                # show stack traces only if ``log.traceback_level`` is ``DEBUG``
                 logging.Logger.exception = debug_exception
             else:
+                # show stack traces as ``ERROR`` log messages
                 logging.Logger.exception = error_exception
 
             new_handler = None
@@ -124,7 +249,9 @@ class PatroniLogger(Thread):
                 if not isinstance(self.log_handler, RotatingFileHandler):
                     new_handler = RotatingFileHandler(os.path.join(config['dir'], __name__))
                 handler = new_handler or self.log_handler
-                handler.maxBytes = int(config.get('file_size', 25000000))
+                if TYPE_CHECKING:  # pragma: no cover
+                    assert isinstance(handler, RotatingFileHandler)
+                handler.maxBytes = int(config.get('file_size', 25000000))  # pyright: ignore [reportGeneralTypeIssues]
                 handler.backupCount = int(config.get('file_num', 4))
             else:
                 if self.log_handler is None or isinstance(self.log_handler, RotatingFileHandler):
@@ -137,7 +264,7 @@ class PatroniLogger(Thread):
             olddateformat = (self._config or {}).get('dateformat') or None
             dateformat = config.get('dateformat') or None  # Convert empty string to `None`
 
-            if oldlogformat != logformat or olddateformat != dateformat or new_handler:
+            if (oldlogformat != logformat or olddateformat != dateformat or new_handler) and handler:
                 handler.setFormatter(logging.Formatter(logformat, dateformat))
 
             if new_handler:
@@ -149,7 +276,14 @@ class PatroniLogger(Thread):
             self._config = config.copy()
             self.update_loggers()
 
-    def _close_old_handlers(self):
+    def _close_old_handlers(self) -> None:
+        """Close old log handlers.
+
+        .. note::
+            It is used to remove different handlers that were configured previous to a reload in the configuration,
+            e.g. if we are switching from :class:`~logging.handlers.RotatingFileHandler` to
+            class:`~logging.StreamHandler` and vice-versa.
+        """
         while True:
             with self.log_handler_lock:
                 if not self._old_handlers:
@@ -160,7 +294,11 @@ class PatroniLogger(Thread):
             except Exception:
                 _LOGGER.exception('Failed to close the old log handler %s', handler)
 
-    def run(self):
+    def run(self) -> None:
+        """Run logger's thread main loop.
+
+        Keep consuming log queue until requested to quit through ``None`` special log record.
+        """
         # switch to QueueHandler only when the thread was started
         with self.log_handler_lock:
             self._root_logger.addHandler(self._queue_handler)
@@ -170,12 +308,17 @@ class PatroniLogger(Thread):
 
         while True:
             self._close_old_handlers()
+            if TYPE_CHECKING:  # pragma: no cover
+                assert self.log_handler is not None
 
             record = self._queue_handler.queue.get(True)
+            # special message that indicates Patroni is shutting down
             if record is None:
                 break
 
             if self._root_logger.level == logging.INFO:
+                # messages like ``Lock owner: postgresql0; I am postgresql1`` will be shown only when stream doesn't
+                # look normal. This is used to reduce chattiness of Patroni logs.
                 if record.msg.startswith('Lock owner: '):
                     prev_record, record = record, None
                 else:
@@ -189,8 +332,10 @@ class PatroniLogger(Thread):
 
             self._queue_handler.queue.task_done()
 
-    def shutdown(self):
+    def shutdown(self) -> None:
+        """Shut down the logger thread."""
         try:
+            # ``None`` is a special message indicating to queue handler that it should quit its main loop.
             self._queue_handler.queue.put_nowait(None)
         except Full:  # Queue is full.
             # It seems that logging is not working, exiting with non-standard exit-code is the best we can do.
@@ -199,9 +344,11 @@ class PatroniLogger(Thread):
         logging.shutdown()
 
     @property
-    def queue_size(self):
+    def queue_size(self) -> int:
+        """Number of log records in the queue."""
         return self._queue_handler.queue.qsize()
 
     @property
-    def records_lost(self):
+    def records_lost(self) -> int:
+        """Number of logging records that have been lost while the queue was full."""
         return self._queue_handler.records_lost

patroni/postgresql/bootstrap.py

@@ -4,41 +4,96 @@ import shlex
 import tempfile
 import time
 
-from ..dcs import RemoteMember
+from typing import Any, Callable, Dict, List, Optional, Union, Tuple, TYPE_CHECKING
+
+from ..async_executor import CriticalTask
+from ..dcs import Leader, Member, RemoteMember
 from ..psycopg import quote_ident, quote_literal
-from ..utils import deep_compare
+from ..utils import deep_compare, unquote
+
+if TYPE_CHECKING:  # pragma: no cover
+    from . import Postgresql
 
 logger = logging.getLogger(__name__)
 
 
 class Bootstrap(object):
 
-    def __init__(self, postgresql):
+    def __init__(self, postgresql: 'Postgresql') -> None:
         self._postgresql = postgresql
         self._running_custom_bootstrap = False
 
     @property
-    def running_custom_bootstrap(self):
+    def running_custom_bootstrap(self) -> bool:
         return self._running_custom_bootstrap
 
     @property
-    def keep_existing_recovery_conf(self):
+    def keep_existing_recovery_conf(self) -> bool:
         return self._running_custom_bootstrap and self._keep_existing_recovery_conf
 
     @staticmethod
-    def process_user_options(tool, options, not_allowed_options, error_handler):
-        user_options = []
+    def process_user_options(tool: str,
+                             options: Union[Any, Dict[str, str], List[Union[str, Dict[str, Any]]]],
+                             not_allowed_options: Tuple[str, ...],
+                             error_handler: Callable[[str], None]) -> List[str]:
+        """Format *options* in a list or dictionary format into command line long form arguments.
 
-        def option_is_allowed(name):
+        .. note::
+            The format of the output of this method is to prepare arguments for use in the ``initdb``
+            method of `self._postgres`.
+
+        :Example:
+
+            The *options* can be defined as a dictionary of key, values to be converted into arguments:
+            >>> Bootstrap.process_user_options('foo', {'foo': 'bar'}, (), print)
+            ['--foo=bar']
+
+            Or as a list of single string arguments
+            >>> Bootstrap.process_user_options('foo', ['yes'], (), print)
+            ['--yes']
+
+            Or as a list of key, value options
+            >>> Bootstrap.process_user_options('foo', [{'foo': 'bar'}], (), print)
+            ['--foo=bar']
+
+            Or a combination of single and key, values
+            >>> Bootstrap.process_user_options('foo', ['yes', {'foo': 'bar'}], (), print)
+            ['--yes', '--foo=bar']
+
+            Options that contain spaces are passed as is to ``subprocess.call``
+            >>> Bootstrap.process_user_options('foo', [{'foo': 'bar baz'}], (), print)
+            ['--foo=bar baz']
+
+            Options that are quoted will be unquoted, so the quotes aren't interpreted
+            literally by the postgres command
+            >>> Bootstrap.process_user_options('foo', [{'foo': '"bar baz"'}], (), print)
+            ['--foo=bar baz']
+
+        .. note::
+            The *error_handler* is called when any of these conditions are met:
+
+            * Key, value dictionaries in the list form contains multiple keys.
+            * If a key is listed in *not_allowed_options*.
+            * If the options list is not in the required structure.
+
+        :param tool: The name of the tool used in error reports to *error_handler*
+        :param options: Options to parse as a list of key, values or single values, or a dictionary
+        :param not_allowed_options: List of keys that cannot be used in the list of key, value formatted options
+        :param error_handler: A function which will be called when an error condition is encountered
+        :returns: List of long form arguments to pass to the named tool
+        """
+        user_options: List[str] = []
+
+        def option_is_allowed(name: str) -> bool:
             ret = name not in not_allowed_options
             if not ret:
                 error_handler('{0} option for {1} is not allowed'.format(name, tool))
             return ret
 
         if isinstance(options, dict):
-            for k, v in options.items():
-                if k and v:
-                    user_options.append('--{0}={1}'.format(k, v))
+            for key, val in options.items():
+                if key and val:
+                    user_options.append('--{0}={1}'.format(key, unquote(val)))
         elif isinstance(options, list):
             for opt in options:
                 if isinstance(opt, str) and option_is_allowed(opt):
@@ -48,7 +103,7 @@ class Bootstrap(object):
                     if len(keys) != 1 or not isinstance(opt[keys[0]], str) or not option_is_allowed(keys[0]):
                         error_handler('Error when parsing {0} key-value option {1}: only one key-value is allowed'
                                       ' and value should be a string'.format(tool, opt[keys[0]]))
-                    user_options.append('--{0}={1}'.format(keys[0], opt[keys[0]]))
+                    user_options.append('--{0}={1}'.format(keys[0], unquote(opt[keys[0]])))
                 else:
                     error_handler('Error when parsing {0} option {1}: value should be string value'
                                   ' or a single key-value pair'.format(tool, opt))
@@ -56,11 +111,11 @@ class Bootstrap(object):
             error_handler('{0} options must be list or dict'.format(tool))
         return user_options
 
-    def _initdb(self, config):
+    def _initdb(self, config: Any) -> bool:
         self._postgresql.set_state('initializing new cluster')
         not_allowed_options = ('pgdata', 'nosync', 'pwfile', 'sync-only', 'version')
 
-        def error_handler(e):
+        def error_handler(e: str) -> None:
             raise Exception(e)
 
         options = self.process_user_options('initdb', config or [], not_allowed_options, error_handler)
@@ -74,9 +129,8 @@ class Bootstrap(object):
                 os.write(fd, self._postgresql.config.superuser['password'].encode('utf-8'))
                 os.close(fd)
                 options.append('--pwfile={0}'.format(pwfile))
-        options = ['-o', ' '.join(options)] if options else []
 
-        ret = self._postgresql.pg_ctl('initdb', *options)
+        ret = self._postgresql.initdb(*options)
         if pwfile:
             os.remove(pwfile)
         if ret:
@@ -85,7 +139,7 @@ class Bootstrap(object):
             self._postgresql.set_state('initdb failed')
         return ret
 
-    def _post_restore(self):
+    def _post_restore(self) -> None:
         self._postgresql.config.restore_configuration_files()
         self._postgresql.configure_server_parameters()
 
@@ -96,7 +150,7 @@ class Bootstrap(object):
         if os.path.exists(trigger_file):
             os.unlink(trigger_file)
 
-    def _custom_bootstrap(self, config):
+    def _custom_bootstrap(self, config: Any) -> bool:
         self._postgresql.set_state('running custom bootstrap script')
         params = [] if config.get('no_params') else ['--scope=' + self._postgresql.scope,
                                                      '--datadir=' + self._postgresql.data_dir]
@@ -116,7 +170,7 @@ class Bootstrap(object):
             self._postgresql.config.remove_recovery_conf()
         return True
 
-    def call_post_bootstrap(self, config):
+    def call_post_bootstrap(self, config: Dict[str, Any]) -> bool:
         """
         runs a script after initdb or custom bootstrap script is called and waits until completion.
         """
@@ -131,7 +185,7 @@ class Bootstrap(object):
                 r['host'] = 'localhost'  # set it to localhost to write into pgpass
 
             env = self._postgresql.config.write_pgpass(r)
-            env['PGOPTIONS'] = '-c synchronous_commit=local'
+            env['PGOPTIONS'] = '-c synchronous_commit=local -c statement_timeout=0'
 
             try:
                 ret = self._postgresql.cancellable.call(shlex.split(cmd) + [connstring], env=env)
@@ -143,7 +197,7 @@ class Bootstrap(object):
                 return False
         return True
 
-    def create_replica(self, clone_member):
+    def create_replica(self, clone_member: Union[Leader, Member, None]) -> Optional[int]:
         """
             create the replica according to the replica_method
             defined by the user.  this is a list, so we need to
@@ -230,7 +284,7 @@ class Bootstrap(object):
         self._postgresql.set_state('stopped')
         return ret
 
-    def basebackup(self, conn_url, env, options):
+    def basebackup(self, conn_url: str, env: Dict[str, str], options: Dict[str, Any]) -> Optional[int]:
         # creates a replica data dir using pg_basebackup.
         # this is the default, built-in create_replica_methods
         # tries twice, then returns failure (as 1)
@@ -265,7 +319,7 @@ class Bootstrap(object):
 
         return ret
 
-    def clone(self, clone_member):
+    def clone(self, clone_member: Union[Leader, Member, None]) -> bool:
         """
              - initialize the replica from an existing member (primary or replica)
              - initialize the replica using the replica creation method that
@@ -278,7 +332,7 @@ class Bootstrap(object):
             self._post_restore()
         return ret
 
-    def bootstrap(self, config):
+    def bootstrap(self, config: Dict[str, Any]) -> bool:
         """ Initialize a new node from scratch and start it. """
         pg_hba = config.get('pg_hba', [])
         method = config.get('method') or 'initdb'
@@ -290,9 +344,9 @@ class Bootstrap(object):
             method = 'initdb'
             do_initialize = self._initdb
         return do_initialize(config.get(method)) and self._postgresql.config.append_pg_hba(pg_hba) \
-            and self._postgresql.config.save_configuration_files() and self._postgresql.start()
+            and self._postgresql.config.save_configuration_files() and bool(self._postgresql.start())
 
-    def create_or_update_role(self, name, password, options):
+    def create_or_update_role(self, name: str, password: Optional[str], options: List[str]) -> None:
         options = list(map(str.upper, options))
         if 'NOLOGIN' not in options and 'LOGIN' not in options:
             options.append('LOGIN')
@@ -322,7 +376,7 @@ END;$$""".format(quote_literal(name), quote_ident(name, self._postgresql.connect
             self._postgresql.query('RESET log_statement')
             self._postgresql.query('RESET pg_stat_statements.track_utility')
 
-    def post_bootstrap(self, config, task):
+    def post_bootstrap(self, config: Dict[str, Any], task: CriticalTask) -> Optional[bool]:
         try:
             postgresql = self._postgresql
             superuser = postgresql.config.superuser

patroni/postgresql/callback_executor.py

@@ -17,7 +17,7 @@ class CallbackAction(str, Enum):
     ON_RELOAD = "on_reload"
     ON_ROLE_CHANGE = "on_role_change"
 
-    def __repr__(self):
+    def __repr__(self) -> str:
         return self.value
 
 
@@ -60,15 +60,17 @@ class CallbackExecutor(CancellableExecutor, Thread):
             self._cmd = cmd
             self._condition.notify()
 
-    def run(self):
+    def run(self) -> None:
         while True:
             with self._condition:
                 if self._cmd is None:
                     self._condition.wait()
                 cmd, self._cmd = self._cmd, None
 
-            with self._lock:
-                if not self._start_process(cmd, close_fds=True):
-                    continue
-            self._process.wait()
-            self._kill_children()
+            if cmd is not None:
+                with self._lock:
+                    if not self._start_process(cmd, close_fds=True):
+                        continue
+                if self._process:
+                    self._process.wait()
+                    self._kill_children()

patroni/postgresql/cancellable.py

@@ -5,6 +5,7 @@ import subprocess
 from patroni.exceptions import PostgresException
 from patroni.utils import polling_loop
 from threading import Lock
+from typing import Any, Dict, List, Optional, Union
 
 logger = logging.getLogger(__name__)
 
@@ -15,13 +16,13 @@ class CancellableExecutor(object):
     There must be only one such process so that AsyncExecutor can easily cancel it.
     """
 
-    def __init__(self):
+    def __init__(self) -> None:
         self._process = None
         self._process_cmd = None
-        self._process_children = []
+        self._process_children: List[psutil.Process] = []
         self._lock = Lock()
 
-    def _start_process(self, cmd, *args, **kwargs):
+    def _start_process(self, cmd: List[str], *args: Any, **kwargs: Any) -> Optional[bool]:
         """This method must be executed only when the `_lock` is acquired"""
 
         try:
@@ -29,10 +30,10 @@ class CancellableExecutor(object):
             self._process_cmd = cmd
             self._process = psutil.Popen(cmd, *args, **kwargs)
         except Exception:
-            return logger.exception('Failed to execute %s',  cmd)
+            return logger.exception('Failed to execute %s', cmd)
         return True
 
-    def _kill_process(self):
+    def _kill_process(self) -> None:
         with self._lock:
             if self._process is not None and self._process.is_running() and not self._process_children:
                 try:
@@ -53,8 +54,8 @@ class CancellableExecutor(object):
                 except psutil.AccessDenied as e:
                     logger.warning('Failed to kill the process: %s', e.msg)
 
-    def _kill_children(self):
-        waitlist = []
+    def _kill_children(self) -> None:
+        waitlist: List[psutil.Process] = []
         with self._lock:
             for child in self._process_children:
                 try:
@@ -69,15 +70,16 @@ class CancellableExecutor(object):
 
 class CancellableSubprocess(CancellableExecutor):
 
-    def __init__(self):
+    def __init__(self) -> None:
         super(CancellableSubprocess, self).__init__()
         self._is_cancelled = False
 
-    def call(self, *args, **kwargs):
+    def call(self, *args: Any, **kwargs: Union[Any, Dict[str, str]]) -> Optional[int]:
         for s in ('stdin', 'stdout', 'stderr'):
             kwargs.pop(s, None)
 
-        communicate = kwargs.pop('communicate', None)
+        communicate: Optional[Dict[str, str]] = kwargs.pop('communicate', None)
+        input_data = None
         if isinstance(communicate, dict):
             input_data = communicate.get('input')
             if input_data:
@@ -96,7 +98,7 @@ class CancellableSubprocess(CancellableExecutor):
                 self._is_cancelled = False
                 started = self._start_process(*args, **kwargs)
 
-            if started:
+            if started and self._process is not None:
                 if isinstance(communicate, dict):
                     communicate['stdout'], communicate['stderr'] = self._process.communicate(input_data)
                 return self._process.wait()
@@ -105,16 +107,16 @@ class CancellableSubprocess(CancellableExecutor):
                 self._process = None
             self._kill_children()
 
-    def reset_is_cancelled(self):
+    def reset_is_cancelled(self) -> None:
         with self._lock:
             self._is_cancelled = False
 
     @property
-    def is_cancelled(self):
+    def is_cancelled(self) -> bool:
         with self._lock:
             return self._is_cancelled
 
-    def cancel(self, kill=False):
+    def cancel(self, kill: bool = False) -> None:
         with self._lock:
             self._is_cancelled = True
             if self._process is None or not self._process.is_running():

patroni/postgresql/citus.py

@@ -4,11 +4,17 @@ import time
 
 from threading import Condition, Event, Thread
 from urllib.parse import urlparse
+from typing import Any, Dict, List, Optional, Union, Tuple, TYPE_CHECKING
 
 from .connection import Connection
-from ..dcs import CITUS_COORDINATOR_GROUP_ID
+from ..dcs import CITUS_COORDINATOR_GROUP_ID, Cluster
 from ..psycopg import connect, quote_ident
 
+if TYPE_CHECKING:  # pragma: no cover
+    from psycopg import Cursor
+    from psycopg2 import cursor
+    from . import Postgresql
+
 CITUS_SLOT_NAME_RE = re.compile(r'^citus_shard_(move|split)_slot(_[1-9][0-9]*){2,3}$')
 logger = logging.getLogger(__name__)
 
@@ -16,7 +22,8 @@ logger = logging.getLogger(__name__)
 class PgDistNode(object):
     """Represents a single row in the `pg_dist_node` table"""
 
-    def __init__(self, group, host, port, event, nodeid=None, timeout=None, cooldown=None):
+    def __init__(self, group: int, host: str, port: int, event: str, nodeid: Optional[int] = None,
+                 timeout: Optional[float] = None, cooldown: Optional[float] = None) -> None:
         self.group = group
         # A weird way of pausing client connections by adding the `-demoted` suffix to the hostname
         self.host = host + ('-demoted' if event == 'before_demote' else '')
@@ -29,7 +36,7 @@ class PgDistNode(object):
         # If transaction was started, we need to COMMIT/ROLLBACK before the deadline
         self.timeout = timeout
         self.cooldown = cooldown or 10000  # 10s by default
-        self.deadline = 0
+        self.deadline: float = 0
 
         # All changes in the pg_dist_node are serialized on the Patroni
         # side by performing them from a thread. The thread, that is
@@ -38,83 +45,85 @@ class PgDistNode(object):
         # the worker, and once it is done notify the calling thread.
         self._event = Event()
 
-    def wait(self):
+    def wait(self) -> None:
         self._event.wait()
 
-    def wakeup(self):
+    def wakeup(self) -> None:
         self._event.set()
 
-    def __eq__(self, other):
+    def __eq__(self, other: Any) -> bool:
         return isinstance(other, PgDistNode) and self.event == other.event\
             and self.host == other.host and self.port == other.port
 
-    def __ne__(self, other):
+    def __ne__(self, other: Any) -> bool:
         return not self == other
 
-    def __str__(self):
+    def __str__(self) -> str:
         return ('PgDistNode(nodeid={0},group={1},host={2},port={3},event={4})'
                 .format(self.nodeid, self.group, self.host, self.port, self.event))
 
-    def __repr__(self):
+    def __repr__(self) -> str:
         return str(self)
 
 
 class CitusHandler(Thread):
 
-    def __init__(self, postgresql, config):
+    def __init__(self, postgresql: 'Postgresql', config: Optional[Dict[str, Union[str, int]]]) -> None:
         super(CitusHandler, self).__init__()
         self.daemon = True
         self._postgresql = postgresql
         self._config = config
         self._connection = Connection()
-        self._pg_dist_node = {}  # Cache of pg_dist_node: {groupid: PgDistNode()}
-        self._tasks = []  # Requests to change pg_dist_node, every task is a `PgDistNode`
-        self._condition = Condition()  # protects _pg_dist_node, _tasks, and _schedule_load_pg_dist_node
-        self._in_flight = None  # Reference to the `PgDistNode` if there is a transaction in progress changing it
+        self._pg_dist_node: Dict[int, PgDistNode] = {}  # Cache of pg_dist_node: {groupid: PgDistNode()}
+        self._tasks: List[PgDistNode] = []  # Requests to change pg_dist_node, every task is a `PgDistNode`
+        self._in_flight: Optional[PgDistNode] = None  # Reference to the `PgDistNode` being changed in a transaction
+        self._schedule_load_pg_dist_node = True  # Flag that "pg_dist_node" should be queried from the database
+        self._condition = Condition()  # protects _pg_dist_node, _tasks, _in_flight, and _schedule_load_pg_dist_node
         self.schedule_cache_rebuild()
 
-    def is_enabled(self):
+    def is_enabled(self) -> bool:
         return isinstance(self._config, dict)
 
-    def group(self):
-        return self._config['group']
+    def group(self) -> Optional[int]:
+        return int(self._config['group']) if isinstance(self._config, dict) else None
 
-    def is_coordinator(self):
+    def is_coordinator(self) -> bool:
         return self.is_enabled() and self.group() == CITUS_COORDINATOR_GROUP_ID
 
-    def is_worker(self):
+    def is_worker(self) -> bool:
         return self.is_enabled() and not self.is_coordinator()
 
-    def set_conn_kwargs(self, kwargs):
-        if self.is_enabled():
+    def set_conn_kwargs(self, kwargs: Dict[str, Any]) -> None:
+        if isinstance(self._config, dict):  # self.is_enabled():
             kwargs.update({'dbname': self._config['database'],
                            'options': '-c statement_timeout=0 -c idle_in_transaction_session_timeout=0'})
             self._connection.set_conn_kwargs(kwargs)
 
-    def schedule_cache_rebuild(self):
+    def schedule_cache_rebuild(self) -> None:
         with self._condition:
             self._schedule_load_pg_dist_node = True
 
-    def on_demote(self):
+    def on_demote(self) -> None:
         with self._condition:
             self._pg_dist_node.clear()
             self._tasks[:] = []
             self._in_flight = None
 
-    def query(self, sql, *params):
+    def query(self, sql: str, *params: Any) -> Union['Cursor[Any]', 'cursor']:
         try:
             logger.debug('query(%s, %s)', sql, params)
             cursor = self._connection.cursor()
-            cursor.execute(sql, params or None)
+            cursor.execute(sql.encode('utf-8'), params or None)
             return cursor
         except Exception as e:
             logger.error('Exception when executing query "%s", (%s): %r', sql, params, e)
             self._connection.close()
-            self._in_flight = None
+            with self._condition:
+                self._in_flight = None
             self.schedule_cache_rebuild()
             raise e
 
-    def load_pg_dist_node(self):
+    def load_pg_dist_node(self) -> bool:
         """Read from the `pg_dist_node` table and put it into the local cache"""
 
         with self._condition:
@@ -132,7 +141,7 @@ class CitusHandler(Thread):
             self._pg_dist_node = {r[1]: PgDistNode(r[1], r[2], r[3], 'after_promote', r[0]) for r in cursor}
         return True
 
-    def sync_pg_dist_node(self, cluster):
+    def sync_pg_dist_node(self, cluster: Cluster) -> None:
         """Maintain the `pg_dist_node` from the coordinator leader every heartbeat loop.
 
         We can't always rely on REST API calls from worker nodes in order
@@ -156,20 +165,22 @@ class CitusHandler(Thread):
                     and leader.data.get('role') in ('master', 'primary') and leader.data.get('state') == 'running':
                 self.add_task('after_promote', group, leader.conn_url)
 
-    def find_task_by_group(self, group):
+    def find_task_by_group(self, group: int) -> Optional[int]:
         for i, task in enumerate(self._tasks):
             if task.group == group:
                 return i
 
-    def pick_task(self):
+    def pick_task(self) -> Tuple[Optional[int], Optional[PgDistNode]]:
         """Returns the tuple(i, task), where `i` - is the task index in the self._tasks list
 
         Tasks are picked by following priorities:
+
         1. If there is already a transaction in progress, pick a task
            that that will change already affected worker primary.
         2. If the coordinator address should be changed - pick a task
            with group=0 (coordinators are always in group 0).
-        3. Pick a task that is the oldest (first from the self._tasks)"""
+        3. Pick a task that is the oldest (first from the self._tasks)
+        """
 
         with self._condition:
             if self._in_flight:
@@ -195,28 +206,33 @@ class CitusHandler(Thread):
                 task.nodeid = self._pg_dist_node[task.group].nodeid
             return i, task
 
-    def update_node(self, task):
+    def update_node(self, task: PgDistNode) -> None:
         if task.nodeid is not None:
             self.query('SELECT pg_catalog.citus_update_node(%s, %s, %s, true, %s)',
                        task.nodeid, task.host, task.port, task.cooldown)
         elif task.event != 'before_demote':
-            task.nodeid = self.query("SELECT pg_catalog.citus_add_node(%s, %s, %s, 'primary', 'default')",
-                                     task.host, task.port, task.group).fetchone()[0]
+            row = self.query("SELECT pg_catalog.citus_add_node(%s, %s, %s, 'primary', 'default')",
+                             task.host, task.port, task.group).fetchone()
+            if row is not None:
+                task.nodeid = row[0]
 
-    def process_task(self, task):
+    def process_task(self, task: PgDistNode) -> bool:
         """Updates a single row in `pg_dist_node` table, optionally in a transaction.
 
-        The transaction is started if we do a demote of the worker node
-        or before promoting the other worker if there is not transaction
-        in progress. And, the transaction it is committed when the
-        switchover/failover completed.
+        The transaction is started if we do a demote of the worker node or before promoting the other worker if
+        there is no transaction in progress. And, the transaction is committed when the switchover/failover completed.
 
-        This method returns `True` if node was updated (optionally,
-        transaction was committed) as an indicator that
-        the `self._pg_dist_node` cache should be updated.
+        .. note:
+            The maximum lifetime of the transaction in progress is controlled outside of this method.
 
-        The maximum lifetime of the transaction in progress
-        is controlled outside of this method."""
+        .. note:
+            Read access to `self._in_flight` isn't protected because we know it can't be changed outside of our thread.
+
+        :param task: reference to a :class:`PgDistNode` object that represents a row to be updated/created.
+        :returns: `True` if the row was succesfully created/updated or transaction in progress
+            was committed as an indicator that the `self._pg_dist_node` cache should be updated,
+            or, if the new transaction was opened, this method returns `False`.
+        """
 
         if task.event == 'after_promote':
             # The after_promote may happen without previous before_demote and/or
@@ -227,7 +243,6 @@ class CitusHandler(Thread):
                 self.update_node(task)
             if self._in_flight:
                 self.query('COMMIT')
-                self._in_flight = None
             return True
         else:  # before_demote, before_promote
             if task.timeout:
@@ -235,31 +250,37 @@ class CitusHandler(Thread):
             if not self._in_flight:
                 self.query('BEGIN')
             self.update_node(task)
-            self._in_flight = task
         return False
 
-    def process_tasks(self):
+    def process_tasks(self) -> None:
         while True:
+            # Read access to `_in_flight` isn't protected because we know it can't be changed outside of our thread.
             if not self._in_flight and not self.load_pg_dist_node():
                 break
 
             i, task = self.pick_task()
-            if not task:
+            if not task or i is None:
                 break
             try:
                 update_cache = self.process_task(task)
             except Exception as e:
                 logger.error('Exception when working with pg_dist_node: %r', e)
-                update_cache = False
+                update_cache = None
             with self._condition:
                 if self._tasks:
                     if update_cache:
                         self._pg_dist_node[task.group] = task
+
+                    if update_cache is False:  # an indicator that process_tasks has started a transaction
+                        self._in_flight = task
+                    else:
+                        self._in_flight = None
+
                     if id(self._tasks[i]) == id(task):
                         self._tasks.pop(i)
             task.wakeup()
 
-    def run(self):
+    def run(self) -> None:
         while True:
             try:
                 with self._condition:
@@ -280,15 +301,23 @@ class CitusHandler(Thread):
             except Exception:
                 logger.exception('run')
 
-    def _add_task(self, task):
+    def _add_task(self, task: PgDistNode) -> bool:
         with self._condition:
             i = self.find_task_by_group(task.group)
 
-            # task.timeout is None is an indicator that it was scheduled
-            # from the sync_pg_dist_node() and we don't want to override
-            # already existing task created from REST API.
-            if task.timeout is None and (i is not None or self._in_flight and self._in_flight.group == task.group):
-                return False
+            # The `PgDistNode.timeout` == None is an indicator that it was scheduled from the sync_pg_dist_node().
+            if task.timeout is None:
+                # We don't want to override the already existing task created from REST API.
+                if i is not None and self._tasks[i].timeout is not None:
+                    return False
+
+                # There is a little race condition with tasks created from REST API - the call made "before" the member
+                # key is updated in DCS. Therefore it is possible that :func:`sync_pg_dist_node` will try to create a
+                # task based on the outdated values of "state"/"role". To solve it we introduce an artificial timeout.
+                # Only when the timeout is reached new tasks could be scheduled from sync_pg_dist_node()
+                if self._in_flight and self._in_flight.group == task.group and self._in_flight.timeout is not None\
+                        and self._in_flight.deadline > time.time():
+                    return False
 
             # Override already existing task for the same worker group
             if i is not None:
@@ -306,32 +335,34 @@ class CitusHandler(Thread):
                 return True
         return False
 
-    def add_task(self, event, group, conn_url, timeout=None, cooldown=None):
+    def add_task(self, event: str, group: int, conn_url: str,
+                 timeout: Optional[float] = None, cooldown: Optional[float] = None) -> Optional[PgDistNode]:
         try:
             r = urlparse(conn_url)
         except Exception as e:
             return logger.error('Failed to parse connection url %s: %r', conn_url, e)
         host = r.hostname
-        port = r.port or 5432
-        task = PgDistNode(group, host, port, event, timeout=timeout, cooldown=cooldown)
-        return task if self._add_task(task) else None
+        if host:
+            port = r.port or 5432
+            task = PgDistNode(group, host, port, event, timeout=timeout, cooldown=cooldown)
+            return task if self._add_task(task) else None
 
-    def handle_event(self, cluster, event):
+    def handle_event(self, cluster: Cluster, event: Dict[str, Any]) -> None:
         if not self.is_alive():
             return
 
-        cluster = cluster.workers.get(event['group'])
-        if not (cluster and cluster.leader and cluster.leader.name == event['leader'] and cluster.leader.conn_url):
+        worker = cluster.workers.get(event['group'])
+        if not (worker and worker.leader and worker.leader.name == event['leader'] and worker.leader.conn_url):
             return
 
         task = self.add_task(event['type'], event['group'],
-                             cluster.leader.conn_url,
-                             event['timeout'], event['cooldown']*1000)
+                             worker.leader.conn_url,
+                             event['timeout'], event['cooldown'] * 1000)
         if task and event['type'] == 'before_demote':
             task.wait()
 
-    def bootstrap(self):
-        if not self.is_enabled():
+    def bootstrap(self) -> None:
+        if not isinstance(self._config, dict):  # self.is_enabled()
             return
 
         conn_kwargs = self._postgresql.config.local_connect_kwargs
@@ -340,7 +371,8 @@ class CitusHandler(Thread):
             conn = connect(**conn_kwargs)
             try:
                 with conn.cursor() as cur:
-                    cur.execute('CREATE DATABASE {0}'.format(quote_ident(self._config['database'], conn)))
+                    cur.execute('CREATE DATABASE {0}'.format(
+                        quote_ident(self._config['database'], conn)).encode('utf-8'))
             finally:
                 conn.close()
 
@@ -364,7 +396,7 @@ class CitusHandler(Thread):
         finally:
             conn.close()
 
-    def adjust_postgres_gucs(self, parameters):
+    def adjust_postgres_gucs(self, parameters: Dict[str, Any]) -> None:
         if not self.is_enabled():
             return
 
@@ -375,15 +407,15 @@ class CitusHandler(Thread):
         parameters['shared_preload_libraries'] = ','.join(['citus'] + shared_preload_libraries)
 
         # if not explicitly set Citus overrides max_prepared_transactions to max_connections*2
-        if parameters.get('max_prepared_transactions') == 0:
+        if parameters['max_prepared_transactions'] == 0:
             parameters['max_prepared_transactions'] = parameters['max_connections'] * 2
 
         # Resharding in Citus implemented using logical replication
         parameters['wal_level'] = 'logical'
 
-    def ignore_replication_slot(self, slot):
-        if self.is_enabled() and self._postgresql.is_leader() and\
+    def ignore_replication_slot(self, slot: Dict[str, str]) -> bool:
+        if isinstance(self._config, dict) and self._postgresql.is_leader() and\
                 slot['type'] == 'logical' and slot['database'] == self._config['database']:
             m = CITUS_SLOT_NAME_RE.match(slot['name'])
-            return m and {'move': 'pgoutput', 'split': 'citus'}.get(m.group(1)) == slot['plugin']
+            return bool(m and {'move': 'pgoutput', 'split': 'citus'}.get(m.group(1)) == slot['plugin'])
         return False

patroni/postgresql/config.py

@@ -6,22 +6,29 @@ import socket
 import stat
 import time
 
+from contextlib import contextmanager
 from urllib.parse import urlparse, parse_qsl, unquote
+from types import TracebackType
+from typing import Any, Collection, Dict, Iterator, List, Optional, Union, Tuple, Type, TYPE_CHECKING
 
-from .validator import CaseInsensitiveDict, recovery_parameters,\
-        transform_postgresql_parameter_value, transform_recovery_parameter_value
-from ..dcs import slot_name_from_member_name, RemoteMember
-from ..exceptions import PatroniFatalException
-from ..utils import compare_values, parse_bool, parse_int, split_host_port, uri, \
-        validate_directory, is_subpath
+from .validator import recovery_parameters, transform_postgresql_parameter_value, transform_recovery_parameter_value
+from ..collections import CaseInsensitiveDict, CaseInsensitiveSet
+from ..dcs import Leader, Member, RemoteMember, slot_name_from_member_name
+from ..exceptions import PatroniFatalException, PostgresConnectionException
+from ..file_perm import pg_perm
+from ..utils import compare_values, parse_bool, parse_int, split_host_port, uri, validate_directory, is_subpath
+from ..validator import IntValidator, EnumValidator
+
+if TYPE_CHECKING:  # pragma: no cover
+    from . import Postgresql
 
 logger = logging.getLogger(__name__)
 
 PARAMETER_RE = re.compile(r'([a-z_]+)\s*=\s*')
 
 
-def conninfo_uri_parse(dsn):
-    ret = {}
+def conninfo_uri_parse(dsn: str) -> Dict[str, str]:
+    ret: Dict[str, str] = {}
     r = urlparse(dsn)
     if r.username:
         ret['user'] = r.username
@@ -29,21 +36,19 @@ def conninfo_uri_parse(dsn):
         ret['password'] = r.password
     if r.path[1:]:
         ret['dbname'] = r.path[1:]
-    hosts = []
-    ports = []
+    hosts: List[str] = []
+    ports: List[str] = []
     for netloc in r.netloc.split('@')[-1].split(','):
-        host = port = None
+        host = None
         if '[' in netloc and ']' in netloc:
-            host = netloc.split(']')[0][1:]
-        tmp = netloc.split(':', 1)
+            tmp = netloc.split(']') + ['']
+            host = tmp[0][1:]
+            netloc = ':'.join(tmp[:2])
+        tmp = netloc.rsplit(':', 1)
         if host is None:
             host = tmp[0]
-        if len(tmp) == 2:
-            host, port = tmp
-        if host is not None:
-            hosts.append(host)
-        if port is not None:
-            ports.append(port)
+        hosts.append(host)
+        ports.append(tmp[1] if len(tmp) == 2 else '')
     if hosts:
         ret['host'] = ','.join(hosts)
     if ports:
@@ -56,7 +61,7 @@ def conninfo_uri_parse(dsn):
     return ret
 
 
-def read_param_value(value):
+def read_param_value(value: str) -> Union[Tuple[None, None], Tuple[str, int]]:
     length = len(value)
     ret = ''
     is_quoted = value[0] == "'"
@@ -76,8 +81,8 @@ def read_param_value(value):
     return (None, None) if is_quoted else (ret, i)
 
 
-def conninfo_parse(dsn):
-    ret = {}
+def conninfo_parse(dsn: str) -> Optional[Dict[str, str]]:
+    ret: Dict[str, str] = {}
     length = len(dsn)
     i = 0
     while i < length:
@@ -96,14 +101,14 @@ def conninfo_parse(dsn):
             return
 
         value, end = read_param_value(dsn[i:])
-        if value is None:
+        if value is None or end is None:
             return
         i += end
         ret[param] = value
     return ret
 
 
-def parse_dsn(value):
+def parse_dsn(value: str) -> Optional[Dict[str, str]]:
     """
     Very simple equivalent of `psycopg2.extensions.parse_dsn` introduced in 2.7.0.
     We are not using psycopg2 function in order to remain compatible with 2.5.4+.
@@ -111,9 +116,9 @@ def parse_dsn(value):
     and sets the `sslmode`, 'gssencmode', and `channel_binding` to `prefer` if it is not present in
     the connection string. This is necessary to simplify comparison of the old and the new values.
 
-    >>> r = parse_dsn('postgresql://u%2Fse:pass@:%2f123,[%2Fhost2]/db%2Fsdf?application_name=mya%2Fpp&ssl=true')
-    >>> r == {'application_name': 'mya/pp', 'host': ',/host2', 'sslmode': 'require',\
-              'password': 'pass', 'port': '/123', 'user': 'u/se', 'gssencmode': 'prefer', 'channel_binding': 'prefer'}
+    >>> r = parse_dsn('postgresql://u%2Fse:pass@:%2f123,[::1]/db%2Fsdf?application_name=mya%2Fpp&ssl=true')
+    >>> r == {'application_name': 'mya/pp', 'host': ',::1', 'sslmode': 'require',\
+              'password': 'pass', 'port': '/123,', 'user': 'u/se', 'gssencmode': 'prefer', 'channel_binding': 'prefer'}
     True
     >>> r = parse_dsn(" host = 'host' dbname = db\\\\ name requiressl=1 ")
     >>> r == {'host': 'host', 'sslmode': 'require', 'gssencmode': 'prefer', 'channel_binding': 'prefer'}
@@ -147,14 +152,14 @@ def parse_dsn(value):
     return ret
 
 
-def strip_comment(value):
+def strip_comment(value: str) -> str:
     i = value.find('#')
     if i > -1:
         value = value[:i].strip()
     return value
 
 
-def read_recovery_param_value(value):
+def read_recovery_param_value(value: str) -> Optional[str]:
     """
     >>> read_recovery_param_value('') is None
     True
@@ -211,7 +216,7 @@ def read_recovery_param_value(value):
     return value
 
 
-def mtime(filename):
+def mtime(filename: str) -> Optional[float]:
     try:
         return os.stat(filename).st_mtime
     except OSError:
@@ -220,35 +225,49 @@ def mtime(filename):
 
 class ConfigWriter(object):
 
-    def __init__(self, filename):
+    def __init__(self, filename: str) -> None:
         self._filename = filename
         self._fd = None
 
-    def __enter__(self):
+    def __enter__(self) -> 'ConfigWriter':
         self._fd = open(self._filename, 'w')
         self.writeline('# Do not edit this file manually!\n# It will be overwritten by Patroni!')
         return self
 
-    def __exit__(self, exc_type, exc_val, exc_tb):
+    def __exit__(self, exc_type: Optional[Type[BaseException]],
+                 exc_val: Optional[BaseException], exc_tb: Optional[TracebackType]) -> None:
         if self._fd:
             self._fd.close()
 
-    def writeline(self, line):
-        self._fd.write(line)
-        self._fd.write('\n')
+    def writeline(self, line: str) -> None:
+        if self._fd:
+            self._fd.write(line)
+            self._fd.write('\n')
 
-    def writelines(self, lines):
+    def writelines(self, lines: List[str]) -> None:
         for line in lines:
             self.writeline(line)
 
     @staticmethod
-    def escape(value):  # Escape (by doubling) any single quotes or backslashes in given string
+    def escape(value: Any) -> str:  # Escape (by doubling) any single quotes or backslashes in given string
         return re.sub(r'([\'\\])', r'\1\1', str(value))
 
-    def write_param(self, param, value):
+    def write_param(self, param: str, value: Any) -> None:
         self.writeline("{0} = '{1}'".format(param, self.escape(value)))
 
 
+def _false_validator(value: Any) -> bool:
+    return False
+
+
+def _bool_validator(value: Any) -> bool:
+    return parse_bool(value) is not None
+
+
+def _bool_is_true_validator(value: Any) -> bool:
+    return parse_bool(value) is True
+
+
 class ConfigHandler(object):
 
     # List of parameters which must be always passed to postmaster as command line options
@@ -266,28 +285,28 @@ class ConfigHandler(object):
     #    check_function -- if the new value is not correct must return `!False`
     #    min_version -- major version of PostgreSQL when parameter was introduced
     CMDLINE_OPTIONS = CaseInsensitiveDict({
-        'listen_addresses': (None, lambda _: False, 90100),
-        'port': (None, lambda _: False, 90100),
-        'cluster_name': (None, lambda _: False, 90500),
-        'wal_level': ('hot_standby', lambda v: v.lower() in ('hot_standby', 'replica', 'logical'), 90100),
-        'hot_standby': ('on', lambda _: False, 90100),
-        'max_connections': (100, lambda v: int(v) >= 25, 90100),
-        'max_wal_senders': (10, lambda v: int(v) >= 3, 90100),
-        'wal_keep_segments': (8, lambda v: int(v) >= 1, 90100),
-        'wal_keep_size': ('128MB', lambda v: parse_int(v, 'MB') >= 16, 130000),
-        'max_prepared_transactions': (0, lambda v: int(v) >= 0, 90100),
-        'max_locks_per_transaction': (64, lambda v: int(v) >= 32, 90100),
-        'track_commit_timestamp': ('off', lambda v: parse_bool(v) is not None, 90500),
-        'max_replication_slots': (10, lambda v: int(v) >= 4, 90400),
-        'max_worker_processes': (8, lambda v: int(v) >= 2, 90400),
-        'wal_log_hints': ('on', lambda _: False, 90400)
+        'listen_addresses': (None, _false_validator, 90100),
+        'port': (None, _false_validator, 90100),
+        'cluster_name': (None, _false_validator, 90500),
+        'wal_level': ('hot_standby', EnumValidator(('hot_standby', 'replica', 'logical')), 90100),
+        'hot_standby': ('on', _bool_is_true_validator, 90100),
+        'max_connections': (100, IntValidator(min=25), 90100),
+        'max_wal_senders': (10, IntValidator(min=3), 90100),
+        'wal_keep_segments': (8, IntValidator(min=1), 90100),
+        'wal_keep_size': ('128MB', IntValidator(min=16, base_unit='MB'), 130000),
+        'max_prepared_transactions': (0, IntValidator(min=0), 90100),
+        'max_locks_per_transaction': (64, IntValidator(min=32), 90100),
+        'track_commit_timestamp': ('off', _bool_validator, 90500),
+        'max_replication_slots': (10, IntValidator(min=4), 90400),
+        'max_worker_processes': (8, IntValidator(min=2), 90400),
+        'wal_log_hints': ('on', _bool_is_true_validator, 90400)
     })
 
-    _RECOVERY_PARAMETERS = set(recovery_parameters.keys())
+    _RECOVERY_PARAMETERS = CaseInsensitiveSet(recovery_parameters.keys())
 
-    def __init__(self, postgresql, config):
+    def __init__(self, postgresql: 'Postgresql', config: Dict[str, Any]) -> None:
         self._postgresql = postgresql
-        self._config_dir = os.path.abspath(config.get('config_dir') or postgresql.data_dir)
+        self._config_dir = os.path.abspath(config.get('config_dir', '') or postgresql.data_dir)
         config_base_name = config.get('config_base_name', 'postgresql')
         self._postgresql_conf = os.path.join(self._config_dir, config_base_name + '.conf')
         self._postgresql_conf_mtime = None
@@ -307,23 +326,32 @@ class ConfigHandler(object):
                                         .format(self._pgpass))
         self._passfile = None
         self._passfile_mtime = None
-        self._synchronous_standby_names = None
         self._postmaster_ctime = None
-        self._current_recovery_params = None
+        self._current_recovery_params: Optional[CaseInsensitiveDict] = None
         self._config = {}
-        self._recovery_params = {}
+        self._recovery_params = CaseInsensitiveDict()
+        self._server_parameters: CaseInsensitiveDict = CaseInsensitiveDict()
         self.reload_config(config)
 
-    def setup_server_parameters(self):
+    def load_current_server_parameters(self) -> None:
+        """Read GUC's values from ``pg_settings`` when Patroni is joining the the postgres that is already running."""
+        exclude = [name.lower() for name, value in self.CMDLINE_OPTIONS.items() if value[1] == _false_validator] \
+            + [name.lower() for name in self._RECOVERY_PARAMETERS]
+        self._server_parameters = CaseInsensitiveDict({r[0]: r[1] for r in self._postgresql.query(
+            "SELECT name, pg_catalog.current_setting(name) FROM pg_catalog.pg_settings"
+            " WHERE (source IN ('command line', 'environment variable') OR sourcefile = %s)"
+            " AND pg_catalog.lower(name) != ALL(%s)", self._postgresql_conf, exclude)})
+
+    def setup_server_parameters(self) -> None:
         self._server_parameters = self.get_server_parameters(self._config)
         self._adjust_recovery_parameters()
 
-    def try_to_create_dir(self, d, msg):
-        d = os.path.join(self._postgresql._data_dir, d)
-        if (not is_subpath(self._postgresql._data_dir, d) or not self._postgresql.data_directory_empty()):
+    def try_to_create_dir(self, d: str, msg: str) -> None:
+        d = os.path.join(self._postgresql.data_dir, d)
+        if (not is_subpath(self._postgresql.data_dir, d) or not self._postgresql.data_directory_empty()):
             validate_directory(d, msg)
 
-    def check_directories(self):
+    def check_directories(self) -> None:
         if "unix_socket_directories" in self._server_parameters:
             for d in self._server_parameters["unix_socket_directories"].split(","):
                 self.try_to_create_dir(d.strip(), "'{}' is defined in unix_socket_directories, {}")
@@ -335,7 +363,11 @@ class ConfigHandler(object):
                                    "'{}' is defined in `postgresql.pgpass`, {}")
 
     @property
-    def _configuration_to_save(self):
+    def config_dir(self) -> str:
+        return self._config_dir
+
+    @property
+    def _configuration_to_save(self) -> List[str]:
         configuration = [os.path.basename(self._postgresql_conf)]
         if 'custom_conf' not in self._config:
             configuration.append(os.path.basename(self._postgresql_base_conf_name))
@@ -345,7 +377,31 @@ class ConfigHandler(object):
             configuration.append('pg_ident.conf')
         return configuration
 
-    def save_configuration_files(self, check_custom_bootstrap=False):
+    def set_file_permissions(self, filename: str) -> None:
+        """Set permissions of file *filename* according to the expected permissions if it resides under PGDATA.
+
+        .. note::
+            Do nothing if the file is not under PGDATA.
+
+        :param filename: path to a file which permissions might need to be adjusted.
+        """
+        if is_subpath(self._postgresql.data_dir, filename):
+            pg_perm.set_permissions_from_data_directory(self._postgresql.data_dir)
+            os.chmod(filename, pg_perm.file_create_mode)
+
+    @contextmanager
+    def config_writer(self, filename: str) -> Iterator[ConfigWriter]:
+        """Create :class:`ConfigWriter` object and set permissions on a *filename*.
+
+        :param filename: path to a config file.
+
+        :yields: :class:`ConfigWriter` object.
+        """
+        with ConfigWriter(filename) as writer:
+            yield writer
+        self.set_file_permissions(filename)
+
+    def save_configuration_files(self, check_custom_bootstrap: bool = False) -> bool:
         """
             copy postgresql.conf to postgresql.conf.backup to be able to retrieve configuration files
             - originally stored as symlinks, those are normally skipped by pg_basebackup
@@ -358,11 +414,12 @@ class ConfigHandler(object):
                     backup_file = os.path.join(self._postgresql.data_dir, f + '.backup')
                     if os.path.isfile(config_file):
                         shutil.copy(config_file, backup_file)
+                        self.set_file_permissions(backup_file)
             except IOError:
                 logger.exception('unable to create backup copies of configuration files')
         return True
 
-    def restore_configuration_files(self):
+    def restore_configuration_files(self) -> None:
         """ restore a previously saved postgresql.conf """
         try:
             for f in self._configuration_to_save:
@@ -371,13 +428,15 @@ class ConfigHandler(object):
                 if not os.path.isfile(config_file):
                     if os.path.isfile(backup_file):
                         shutil.copy(backup_file, config_file)
+                        self.set_file_permissions(config_file)
                     # Previously we didn't backup pg_ident.conf, if file is missing just create empty
                     elif f == 'pg_ident.conf':
                         open(config_file, 'w').close()
+                        self.set_file_permissions(config_file)
         except IOError:
             logger.exception('unable to restore configuration files from backup')
 
-    def write_postgresql_conf(self, configuration=None):
+    def write_postgresql_conf(self, configuration: Optional[CaseInsensitiveDict] = None) -> None:
         # rename the original configuration if it is necessary
         if 'custom_conf' not in self._config and not os.path.exists(self._postgresql_base_conf):
             os.rename(self._postgresql_conf, self._postgresql_base_conf)
@@ -387,11 +446,12 @@ class ConfigHandler(object):
         if self._postgresql.enforce_hot_standby_feedback:
             configuration['hot_standby_feedback'] = 'on'
 
-        with ConfigWriter(self._postgresql_conf) as f:
+        with self.config_writer(self._postgresql_conf) as f:
             include = self._config.get('custom_conf') or self._postgresql_base_conf_name
             f.writeline("include '{0}'\n".format(ConfigWriter.escape(include)))
             for name, value in sorted((configuration).items()):
-                value = transform_postgresql_parameter_value(self._postgresql.major_version, name, value)
+                value = transform_postgresql_parameter_value(self._postgresql.major_version, name, value,
+                                                             self._postgresql.available_gucs)
                 if value is not None and\
                         (name != 'hba_file' or not self._postgresql.bootstrap.running_custom_bootstrap):
                     f.write_param(name, value)
@@ -412,13 +472,14 @@ class ConfigHandler(object):
                 if not self._postgresql.bootstrap.keep_existing_recovery_conf:
                     self._sanitize_auto_conf()
 
-    def append_pg_hba(self, config):
+    def append_pg_hba(self, config: List[str]) -> bool:
         if not self.hba_file and not self._config.get('pg_hba'):
             with open(self._pg_hba_conf, 'a') as f:
                 f.write('\n{}\n'.format('\n'.join(config)))
+            self.set_file_permissions(self._pg_hba_conf)
         return True
 
-    def replace_pg_hba(self):
+    def replace_pg_hba(self) -> Optional[bool]:
         """
         Replace pg_hba.conf content in the PGDATA if hba_file is not defined in the
         `postgresql.parameters` and pg_hba is defined in `postgresql` configuration section.
@@ -435,18 +496,18 @@ class ConfigHandler(object):
                                   self.local_replication_address['host'], self.local_replication_address['port'],
                                   0, socket.SOCK_STREAM, socket.IPPROTO_TCP)})
 
-            with ConfigWriter(self._pg_hba_conf) as f:
+            with self.config_writer(self._pg_hba_conf) as f:
                 for address, t in addresses.items():
                     f.writeline((
                         '{0}\treplication\t{1}\t{3}\ttrust\n'
                         '{0}\tall\t{2}\t{3}\ttrust'
                     ).format(t, self.replication['username'], self._superuser.get('username') or 'all', address))
         elif not self.hba_file and self._config.get('pg_hba'):
-            with ConfigWriter(self._pg_hba_conf) as f:
+            with self.config_writer(self._pg_hba_conf) as f:
                 f.writelines(self._config['pg_hba'])
             return True
 
-    def replace_pg_ident(self):
+    def replace_pg_ident(self) -> Optional[bool]:
         """
         Replace pg_ident.conf content in the PGDATA if ident_file is not defined in the
         `postgresql.parameters` and pg_ident is defined in the `postgresql` section.
@@ -455,12 +516,12 @@ class ConfigHandler(object):
         """
 
         if not self.ident_file and self._config.get('pg_ident'):
-            with ConfigWriter(self._pg_ident_conf) as f:
+            with self.config_writer(self._pg_ident_conf) as f:
                 f.writelines(self._config['pg_ident'])
             return True
 
-    def primary_conninfo_params(self, member):
-        if not (member and member.conn_url) or member.name == self._postgresql.name:
+    def primary_conninfo_params(self, member: Union[Leader, Member, None]) -> Optional[Dict[str, Any]]:
+        if not member or not member.conn_url or member.name == self._postgresql.name:
             return None
         ret = member.conn_kwargs(self.replication)
         ret['application_name'] = self._postgresql.name
@@ -475,7 +536,7 @@ class ConfigHandler(object):
             del ret['dbname']
         return ret
 
-    def format_dsn(self, params, include_dbname=False):
+    def format_dsn(self, params: Dict[str, Any], include_dbname: bool = False) -> str:
         # A list of keywords that can be found in a conninfo string. Follows what is acceptable by libpq
         keywords = ('dbname', 'user', 'passfile' if params.get('passfile') else 'password', 'host', 'port',
                     'sslmode', 'sslcompression', 'sslcert', 'sslkey', 'sslpassword', 'sslrootcert', 'sslcrl',
@@ -491,13 +552,13 @@ class ConfigHandler(object):
         else:
             skip = {'dbname'}
 
-        def escape(value):
+        def escape(value: Any) -> str:
             return re.sub(r'([\'\\ ])', r'\\\1', str(value))
 
         return ' '.join('{0}={1}'.format(kw, escape(params[kw])) for kw in keywords
                         if kw not in skip and params.get(kw) is not None)
 
-    def _write_recovery_params(self, fd, recovery_params):
+    def _write_recovery_params(self, fd: ConfigWriter, recovery_params: CaseInsensitiveDict) -> None:
         if self._postgresql.major_version >= 90500:
             pause_at_recovery_target = parse_bool(recovery_params.pop('pause_at_recovery_target', None))
             if pause_at_recovery_target is not None:
@@ -513,15 +574,16 @@ class ConfigHandler(object):
                     self._passfile_mtime = mtime(self._pgpass)
                 value = self.format_dsn(value)
             else:
-                value = transform_recovery_parameter_value(self._postgresql.major_version, name, value)
+                value = transform_recovery_parameter_value(self._postgresql.major_version, name, value,
+                                                           self._postgresql.available_gucs)
                 if value is None:
                     continue
             fd.write_param(name, value)
 
-    def build_recovery_params(self, member):
-        recovery_params = CaseInsensitiveDict({p: v for p, v in self.get('recovery_conf', {}).items()
-                                               if not p.lower().startswith('recovery_target') and
-                                               p.lower() not in ('primary_conninfo', 'primary_slot_name')})
+    def build_recovery_params(self, member: Union[Leader, Member, None]) -> CaseInsensitiveDict:
+        recovery_params = CaseInsensitiveDict({p: v for p, v in (self.get('recovery_conf') or {}).items()
+                                               if not p.lower().startswith('recovery_target')
+                                               and p.lower() not in ('primary_conninfo', 'primary_slot_name')})
         recovery_params.update({'standby_mode': 'on', 'recovery_target_timeline': 'latest'})
         if self._postgresql.major_version >= 120000:
             # on pg12 we want to protect from following params being set in one of included files
@@ -550,26 +612,43 @@ class ConfigHandler(object):
         recovery_params.update({p: member.data.get(p) for p in standby_cluster_params if member and member.data.get(p)})
         return recovery_params
 
-    def recovery_conf_exists(self):
+    def recovery_conf_exists(self) -> bool:
         if self._postgresql.major_version >= 120000:
             return os.path.exists(self._standby_signal) or os.path.exists(self._recovery_signal)
         return os.path.exists(self._recovery_conf)
 
     @property
-    def triggerfile_good_name(self):
+    def triggerfile_good_name(self) -> str:
         return 'trigger_file' if self._postgresql.major_version < 120000 else 'promote_trigger_file'
 
     @property
-    def _triggerfile_wrong_name(self):
+    def _triggerfile_wrong_name(self) -> str:
         return 'trigger_file' if self._postgresql.major_version >= 120000 else 'promote_trigger_file'
 
     @property
-    def _recovery_parameters_to_compare(self):
-        skip_params = {'pause_at_recovery_target', 'recovery_target_inclusive',
-                       'recovery_target_action', 'standby_mode', self._triggerfile_wrong_name}
-        return self._RECOVERY_PARAMETERS - skip_params
+    def _recovery_parameters_to_compare(self) -> CaseInsensitiveSet:
+        skip_params = CaseInsensitiveSet({'pause_at_recovery_target', 'recovery_target_inclusive',
+                                          'recovery_target_action', 'standby_mode', self._triggerfile_wrong_name})
+        return CaseInsensitiveSet(self._RECOVERY_PARAMETERS - skip_params)
 
-    def _read_recovery_params(self):
+    def _read_recovery_params(self) -> Tuple[Optional[CaseInsensitiveDict], bool]:
+        """Read current recovery parameters values.
+
+        .. note::
+            We query Postgres only if we detected that Postgresql was restarted
+            or when at least one of the following files was updated:
+
+                * ``postgresql.conf``;
+                * ``postgresql.auto.conf``;
+                * ``passfile`` that is used in the ``primary_conninfo``.
+
+        :returns: a tuple with two elements:
+
+            * :class:`CaseInsensitiveDict` object with current values of recovery parameters,
+              or ``None`` if no configuration files were updated;
+
+            * ``True`` if new values of recovery parameters were queried, ``False`` otherwise.
+        """
         if self._postgresql.is_starting():
             return None, False
 
@@ -586,21 +665,30 @@ class ConfigHandler(object):
 
         try:
             values = self._get_pg_settings(self._recovery_parameters_to_compare).values()
-            values = {p[0]: [p[1], p[4] == 'postmaster', p[5]] for p in values}
+            values = CaseInsensitiveDict({p[0]: [p[1], p[4] == 'postmaster', p[5]] for p in values})
             self._postgresql_conf_mtime = pg_conf_mtime
             self._auto_conf_mtime = auto_conf_mtime
             self._postmaster_ctime = postmaster_ctime
-        except Exception:
+        except Exception as exc:
+            if all((isinstance(exc, PostgresConnectionException),
+                    self._postgresql_conf_mtime == pg_conf_mtime,
+                    self._auto_conf_mtime == auto_conf_mtime,
+                    self._passfile_mtime == passfile_mtime,
+                    self._postmaster_ctime != postmaster_ctime)):
+                # We detected that the connection to postgres fails, but the process creation time of the postmaster
+                # doesn't match the old value. It is an indicator that Postgres crashed and either doing crash
+                # recovery or down. In this case we return values like nothing changed in the config.
+                return None, False
             values = None
         return values, True
 
-    def _read_recovery_params_pre_v12(self):
+    def _read_recovery_params_pre_v12(self) -> Tuple[Optional[CaseInsensitiveDict], bool]:
         recovery_conf_mtime = mtime(self._recovery_conf)
         passfile_mtime = mtime(self._passfile) if self._passfile else False
         if recovery_conf_mtime == self._recovery_conf_mtime and passfile_mtime == self._passfile_mtime:
             return None, False
 
-        values = {}
+        values = CaseInsensitiveDict()
         with open(self._recovery_conf, 'r') as f:
             for line in f:
                 line = line.strip()
@@ -610,7 +698,7 @@ class ConfigHandler(object):
                 match = PARAMETER_RE.match(line)
                 if match:
                     value = read_recovery_param_value(line[match.end():])
-                if value is None:
+                if match is None or value is None:
                     return None, True
                 values[match.group(1)] = [value, True]
             self._recovery_conf_mtime = recovery_conf_mtime
@@ -619,7 +707,7 @@ class ConfigHandler(object):
         values.update({param: ['', True] for param in self._recovery_parameters_to_compare if param not in values})
         return values, True
 
-    def _check_passfile(self, passfile, wanted_primary_conninfo):
+    def _check_passfile(self, passfile: str, wanted_primary_conninfo: Dict[str, Any]) -> bool:
         # If there is a passfile in the primary_conninfo try to figure out that
         # the passfile contains the line(s) allowing connection to the given node.
         # We assume that the passfile was created by Patroni and therefore doing
@@ -628,7 +716,7 @@ class ConfigHandler(object):
         if passfile_mtime:
             try:
                 with open(passfile) as f:
-                    wanted_lines = self._pgpass_line(wanted_primary_conninfo).splitlines()
+                    wanted_lines = (self._pgpass_line(wanted_primary_conninfo) or '').splitlines()
                     file_lines = f.read().splitlines()
                     if set(wanted_lines) == set(file_lines):
                         self._passfile = passfile
@@ -638,7 +726,8 @@ class ConfigHandler(object):
                 logger.info('Failed to read %s', passfile)
         return False
 
-    def _check_primary_conninfo(self, primary_conninfo, wanted_primary_conninfo):
+    def _check_primary_conninfo(self, primary_conninfo: Dict[str, Any],
+                                wanted_primary_conninfo: Dict[str, Any]) -> bool:
         # first we will cover corner cases, when we are replicating from somewhere while shouldn't
         # or there is no primary_conninfo but we should replicate from some specific node.
         if not wanted_primary_conninfo:
@@ -667,7 +756,7 @@ class ConfigHandler(object):
 
         return all(str(primary_conninfo.get(p)) == str(v) for p, v in wanted_primary_conninfo.items() if v is not None)
 
-    def check_recovery_conf(self, member):
+    def check_recovery_conf(self, member: Union[Leader, Member, None]) -> Tuple[bool, bool]:
         """Returns a tuple. The first boolean element indicates that recovery params don't match
            and the second is set to `True` if the restart is required in order to apply new values"""
 
@@ -701,7 +790,7 @@ class ConfigHandler(object):
             else:  # empty string, primary_conninfo is not in the config
                 primary_conninfo[0] = {}
 
-        if not self._postgresql.is_starting():
+        if not self._postgresql.is_starting() and self._current_recovery_params:
             # when wal receiver is alive take primary_slot_name from pg_stat_wal_receiver
             wal_receiver_primary_slot_name = self._postgresql.primary_slot_name()
             if not wal_receiver_primary_slot_name and self._postgresql.primary_conninfo():
@@ -715,11 +804,11 @@ class ConfigHandler(object):
                                   and not self._postgresql.cb_called
                                   and not self._postgresql.is_starting())}
 
-        def record_missmatch(mtype):
+        def record_missmatch(mtype: bool) -> None:
             required['restart' if mtype else 'reload'] += 1
 
         wanted_recovery_params = self.build_recovery_params(member)
-        for param, value in self._current_recovery_params.items():
+        for param, value in (self._current_recovery_params or {}).items():
             # Skip certain parameters defined in the included postgres config files
             # if we know that they are not specified in the patroni configuration.
             if len(value) > 2 and value[2] not in (self._postgresql_conf, self._auto_conf) and \
@@ -741,25 +830,25 @@ class ConfigHandler(object):
         return required['restart'] + required['reload'] > 0, required['restart'] > 0
 
     @staticmethod
-    def _remove_file_if_exists(name):
+    def _remove_file_if_exists(name: str) -> None:
         if os.path.isfile(name) or os.path.islink(name):
             os.unlink(name)
 
     @staticmethod
-    def _pgpass_line(record):
+    def _pgpass_line(record: Dict[str, Any]) -> Optional[str]:
         if 'password' in record:
-            def escape(value):
+            def escape(value: Any) -> str:
                 return re.sub(r'([:\\])', r'\\\1', str(value))
 
             record = {n: escape(record.get(n) or '*') for n in ('host', 'port', 'user', 'password')}
             # 'host' could be several comma-separated hostnames, in this case
             # we need to write on pgpass line per host
             line = ''
-            for hostname in record.get('host').split(','):
+            for hostname in record['host'].split(','):
                 line += hostname + ':{port}:*:{user}:{password}'.format(**record) + '\n'
             return line.rstrip()
 
-    def write_pgpass(self, record):
+    def write_pgpass(self, record: Dict[str, Any]) -> Dict[str, str]:
         line = self._pgpass_line(record)
         if not line:
             return os.environ.copy()
@@ -770,37 +859,38 @@ class ConfigHandler(object):
 
         return {**os.environ, 'PGPASSFILE': self._pgpass}
 
-    def write_recovery_conf(self, recovery_params):
+    def write_recovery_conf(self, recovery_params: CaseInsensitiveDict) -> None:
         self._recovery_params = recovery_params
         if self._postgresql.major_version >= 120000:
             if parse_bool(recovery_params.pop('standby_mode', None)):
                 open(self._standby_signal, 'w').close()
+                self.set_file_permissions(self._standby_signal)
             else:
                 self._remove_file_if_exists(self._standby_signal)
                 open(self._recovery_signal, 'w').close()
+                self.set_file_permissions(self._recovery_signal)
 
-            def restart_required(name):
+            def restart_required(name: str) -> bool:
                 if self._postgresql.major_version >= 140000:
                     return False
                 return name == 'restore_command' or (self._postgresql.major_version < 130000
                                                      and name in ('primary_conninfo', 'primary_slot_name'))
 
-            self._current_recovery_params = {n: [v, restart_required(n), self._postgresql_conf]
-                                             for n, v in recovery_params.items()}
+            self._current_recovery_params = CaseInsensitiveDict({n: [v, restart_required(n), self._postgresql_conf]
+                                                                 for n, v in recovery_params.items()})
         else:
-            with ConfigWriter(self._recovery_conf) as f:
-                os.chmod(self._recovery_conf, stat.S_IWRITE | stat.S_IREAD)
+            with self.config_writer(self._recovery_conf) as f:
                 self._write_recovery_params(f, recovery_params)
 
-    def remove_recovery_conf(self):
+    def remove_recovery_conf(self) -> None:
         for name in (self._recovery_conf, self._standby_signal, self._recovery_signal):
             self._remove_file_if_exists(name)
-        self._recovery_params = {}
+        self._recovery_params = CaseInsensitiveDict()
         self._current_recovery_params = None
 
-    def _sanitize_auto_conf(self):
+    def _sanitize_auto_conf(self) -> None:
         overwrite = False
-        lines = []
+        lines: List[str] = []
 
         if os.path.exists(self._auto_conf):
             try:
@@ -818,12 +908,13 @@ class ConfigHandler(object):
         if overwrite:
             try:
                 with open(self._auto_conf, 'w') as f:
+                    self.set_file_permissions(self._auto_conf)
                     for raw_line in lines:
                         f.write(raw_line)
             except Exception:
                 logger.exception('Failed to remove some unwanted parameters from %s', self._auto_conf)
 
-    def _adjust_recovery_parameters(self):
+    def _adjust_recovery_parameters(self) -> None:
         # It is not strictly necessary, but we can make patroni configs crossi-compatible with all postgres versions.
         recovery_conf = {n: v for n, v in self._server_parameters.items() if n.lower() in self._RECOVERY_PARAMETERS}
         if recovery_conf:
@@ -834,18 +925,20 @@ class ConfigHandler(object):
             if self.triggerfile_good_name not in self._config['recovery_conf'] and value:
                 self._config['recovery_conf'][self.triggerfile_good_name] = value
 
-    def get_server_parameters(self, config):
+    def get_server_parameters(self, config: Dict[str, Any]) -> CaseInsensitiveDict:
         parameters = config['parameters'].copy()
         listen_addresses, port = split_host_port(config['listen'], 5432)
         parameters.update(cluster_name=self._postgresql.scope, listen_addresses=listen_addresses, port=str(port))
-        if config.get('synchronous_mode', False):
-            if self._synchronous_standby_names is None:
-                if config.get('synchronous_mode_strict', False):
+        if not self._postgresql.global_config or self._postgresql.global_config.is_synchronous_mode:
+            synchronous_standby_names = self._server_parameters.get('synchronous_standby_names')
+            if synchronous_standby_names is None:
+                if self._postgresql.global_config and self._postgresql.global_config.is_synchronous_mode_strict\
+                        and self._postgresql.role in ('master', 'primary', 'promoted'):
                     parameters['synchronous_standby_names'] = '*'
                 else:
                     parameters.pop('synchronous_standby_names', None)
             else:
-                parameters['synchronous_standby_names'] = self._synchronous_standby_names
+                parameters['synchronous_standby_names'] = synchronous_standby_names
 
         # Handle hot_standby <-> replica rename
         if parameters.get('wal_level') == ('hot_standby' if self._postgresql.major_version >= 90600 else 'replica'):
@@ -859,24 +952,24 @@ class ConfigHandler(object):
             parameters.setdefault('wal_keep_size', str(int(wal_keep_segments) * 16) + 'MB')
         elif self._postgresql.major_version:
             wal_keep_size = parse_int(parameters.pop('wal_keep_size', self.CMDLINE_OPTIONS['wal_keep_size'][0]), 'MB')
-            parameters.setdefault('wal_keep_segments', int((wal_keep_size + 8) / 16))
+            parameters.setdefault('wal_keep_segments', int(((wal_keep_size or 0) + 8) / 16))
 
         self._postgresql.citus_handler.adjust_postgres_gucs(parameters)
 
-        ret = CaseInsensitiveDict({k: v for k, v in parameters.items() if not self._postgresql.major_version or
-                                   self._postgresql.major_version >= self.CMDLINE_OPTIONS.get(k, (0, 1, 90100))[2]})
+        ret = CaseInsensitiveDict({k: v for k, v in parameters.items() if not self._postgresql.major_version
+                                   or self._postgresql.major_version >= self.CMDLINE_OPTIONS.get(k, (0, 1, 90100))[2]})
         ret.update({k: os.path.join(self._config_dir, ret[k]) for k in ('hba_file', 'ident_file') if k in ret})
         return ret
 
     @staticmethod
-    def _get_unix_local_address(unix_socket_directories):
+    def _get_unix_local_address(unix_socket_directories: str) -> str:
         for d in unix_socket_directories.split(','):
             d = d.strip()
             if d.startswith('/'):  # Only absolute path can be used to connect via unix-socket
                 return d
         return ''
 
-    def _get_tcp_local_address(self):
+    def _get_tcp_local_address(self) -> str:
         listen_addresses = self._server_parameters['listen_addresses'].split(',')
 
         for la in listen_addresses:
@@ -885,7 +978,7 @@ class ConfigHandler(object):
         return listen_addresses[0].strip()  # can't use localhost, take first address from listen_addresses
 
     @property
-    def local_connect_kwargs(self):
+    def local_connect_kwargs(self) -> Dict[str, Any]:
         ret = self._local_address.copy()
         # add all of the other connection settings that are available
         ret.update(self._superuser)
@@ -901,7 +994,7 @@ class ConfigHandler(object):
                     'options': '-c statement_timeout=2000'})
         return ret
 
-    def resolve_connection_addresses(self):
+    def resolve_connection_addresses(self) -> None:
         port = self._server_parameters['port']
         tcp_local_address = self._get_tcp_local_address()
         netloc = self._config.get('connect_address') or tcp_local_address + ':' + port
@@ -921,19 +1014,21 @@ class ConfigHandler(object):
         self._postgresql.connection_string = uri('postgres', netloc, self._postgresql.database)
         self._postgresql.set_connection_kwargs(self.local_connect_kwargs)
 
-    def _get_pg_settings(self, names):
+    def _get_pg_settings(self, names: Collection[str]) -> Dict[Any, Tuple[Any, ...]]:
         return {r[0]: r for r in self._postgresql.query(('SELECT name, setting, unit, vartype, context, sourcefile'
-                                                         + ' FROM pg_catalog.pg_settings ' +
-                                                         ' WHERE pg_catalog.lower(name) = ANY(%s)'),
+                                                         + ' FROM pg_catalog.pg_settings '
+                                                         + ' WHERE pg_catalog.lower(name) = ANY(%s)'),
                                                         [n.lower() for n in names])}
 
     @staticmethod
-    def _handle_wal_buffers(old_values, changes):
-        wal_block_size = parse_int(old_values['wal_block_size'][1])
+    def _handle_wal_buffers(old_values: Dict[Any, Tuple[Any, ...]], changes: CaseInsensitiveDict) -> None:
+        wal_block_size = parse_int(old_values['wal_block_size'][1]) or 8192
         wal_segment_size = old_values['wal_segment_size']
-        wal_segment_unit = parse_int(wal_segment_size[2], 'B') if wal_segment_size[2][0].isdigit() else 1
-        wal_segment_size = parse_int(wal_segment_size[1]) * wal_segment_unit / wal_block_size
-        default_wal_buffers = min(max(parse_int(old_values['shared_buffers'][1]) / 32, 8), wal_segment_size)
+        wal_segment_unit = parse_int(wal_segment_size[2], 'B') or 8192 \
+            if wal_segment_size[2] is not None and wal_segment_size[2][0].isdigit() else 1
+        wal_segment_size = parse_int(wal_segment_size[1]) or (16777216 if wal_segment_size[2] is None else 2048)
+        wal_segment_size *= wal_segment_unit / wal_block_size
+        default_wal_buffers = min(max((parse_int(old_values['shared_buffers'][1]) or 16384) / 32, 8), wal_segment_size)
 
         wal_buffers = old_values['wal_buffers']
         new_value = str(changes['wal_buffers'] or -1)
@@ -944,7 +1039,7 @@ class ConfigHandler(object):
         if new_value == old_value:
             del changes['wal_buffers']
 
-    def reload_config(self, config, sighup=False):
+    def reload_config(self, config: Dict[str, Any], sighup: bool = False) -> None:
         self._superuser = config['authentication'].get('superuser', {})
         server_parameters = self.get_server_parameters(config)
 
@@ -955,6 +1050,7 @@ class ConfigHandler(object):
             changes.update({p: None for p in self._server_parameters.keys()
                             if not (p in changes or p.lower() in self._RECOVERY_PARAMETERS)})
             if changes:
+                undef = []
                 if 'wal_buffers' in changes:  # we need to calculate the default value of wal_buffers
                     undef = [p for p in ('shared_buffers', 'wal_segment_size', 'wal_block_size') if p not in changes]
                     changes.update({p: None for p in undef})
@@ -1029,31 +1125,31 @@ class ConfigHandler(object):
             if self._postgresql.major_version >= 90500:
                 time.sleep(1)
                 try:
-                    pending_restart = self._postgresql.query(
-                        'SELECT COUNT(*) FROM pg_catalog.pg_settings WHERE pg_catalog.lower(name) != ALL(%s)'
-                        ' AND pending_restart', [n.lower() for n in self._RECOVERY_PARAMETERS]).fetchone()[0] > 0
+                    pending_restart = (self._postgresql.query(
+                        'SELECT COUNT(*) FROM pg_catalog.pg_settings'
+                        ' WHERE pg_catalog.lower(name) != ALL(%s) AND pending_restart',
+                        [n.lower() for n in self._RECOVERY_PARAMETERS]).fetchone() or (0,))[0] > 0
                     self._postgresql.set_pending_restart(pending_restart)
                 except Exception as e:
                     logger.warning('Exception %r when running query', e)
         else:
             logger.info('No PostgreSQL configuration items changed, nothing to reload.')
 
-    def set_synchronous_standby_names(self, value):
+    def set_synchronous_standby_names(self, value: Optional[str]) -> Optional[bool]:
         """Updates synchronous_standby_names and reloads if necessary.
         :returns: True if value was updated."""
-        if value != self._synchronous_standby_names:
+        if value != self._server_parameters.get('synchronous_standby_names'):
             if value is None:
                 self._server_parameters.pop('synchronous_standby_names', None)
             else:
                 self._server_parameters['synchronous_standby_names'] = value
-            self._synchronous_standby_names = value
             if self._postgresql.state == 'running':
                 self.write_postgresql_conf()
                 self._postgresql.reload()
             return True
 
     @property
-    def effective_configuration(self):
+    def effective_configuration(self) -> CaseInsensitiveDict:
         """It might happen that the current value of one (or more) below parameters stored in
         the controldata is higher than the value stored in the global cluster configuration.
 
@@ -1088,7 +1184,7 @@ class ConfigHandler(object):
                 continue
 
             cvalue = parse_int(data[cname])
-            if cvalue > value:
+            if cvalue is not None and value is not None and cvalue > value:
                 effective_configuration[name] = cvalue
                 self._postgresql.set_pending_restart(True)
 
@@ -1112,35 +1208,38 @@ class ConfigHandler(object):
         return effective_configuration
 
     @property
-    def replication(self):
+    def replication(self) -> Dict[str, Any]:
         return self._config['authentication']['replication']
 
     @property
-    def superuser(self):
+    def superuser(self) -> Dict[str, Any]:
         return self._superuser
 
     @property
-    def rewind_credentials(self):
+    def rewind_credentials(self) -> Dict[str, Any]:
         return self._config['authentication'].get('rewind', self._superuser) \
-                if self._postgresql.major_version >= 110000 else self._superuser
+            if self._postgresql.major_version >= 110000 else self._superuser
 
     @property
-    def ident_file(self):
+    def ident_file(self) -> Optional[str]:
         ident_file = self._server_parameters.get('ident_file')
         return None if ident_file == self._pg_ident_conf else ident_file
 
     @property
-    def hba_file(self):
+    def hba_file(self) -> Optional[str]:
         hba_file = self._server_parameters.get('hba_file')
         return None if hba_file == self._pg_hba_conf else hba_file
 
     @property
-    def pg_hba_conf(self):
+    def pg_hba_conf(self) -> str:
         return self._pg_hba_conf
 
     @property
-    def postgresql_conf(self):
+    def postgresql_conf(self) -> str:
         return self._postgresql_conf
 
-    def get(self, key, default=None):
+    def get(self, key: str, default: Optional[Any] = None) -> Optional[Any]:
         return self._config.get(key, default)
+
+    def restore_command(self) -> Optional[str]:
+        return (self.get('recovery_conf') or {}).get('restore_command')

patroni/postgresql/connection.py

@@ -2,6 +2,10 @@ import logging
 
 from contextlib import contextmanager
 from threading import Lock
+from typing import Any, Dict, Iterator, Union, TYPE_CHECKING
+if TYPE_CHECKING:  # pragma: no cover
+    from psycopg import Connection as Connection3, Cursor
+    from psycopg2 import connection, cursor
 
 from .. import psycopg
 
@@ -9,29 +13,30 @@ logger = logging.getLogger(__name__)
 
 
 class Connection(object):
+    server_version: int
 
-    def __init__(self):
+    def __init__(self) -> None:
         self._lock = Lock()
         self._connection = None
         self._cursor_holder = None
 
-    def set_conn_kwargs(self, conn_kwargs):
+    def set_conn_kwargs(self, conn_kwargs: Dict[str, Any]) -> None:
         self._conn_kwargs = conn_kwargs
 
-    def get(self):
+    def get(self) -> Union['connection', 'Connection3[Any]']:
         with self._lock:
             if not self._connection or self._connection.closed != 0:
                 self._connection = psycopg.connect(**self._conn_kwargs)
-                self.server_version = self._connection.server_version
+                self.server_version = getattr(self._connection, 'server_version', 0)
         return self._connection
 
-    def cursor(self):
+    def cursor(self) -> Union['cursor', 'Cursor[Any]']:
         if not self._cursor_holder or self._cursor_holder.closed or self._cursor_holder.connection.closed != 0:
             logger.info("establishing a new patroni connection to the postgres cluster")
             self._cursor_holder = self.get().cursor()
         return self._cursor_holder
 
-    def close(self):
+    def close(self) -> None:
         if self._connection and self._connection.closed == 0:
             self._connection.close()
             logger.info("closed patroni connection to the postgresql cluster")
@@ -39,7 +44,7 @@ class Connection(object):
 
 
 @contextmanager
-def get_connection_cursor(**kwargs):
+def get_connection_cursor(**kwargs: Any) -> Iterator[Union['cursor', 'Cursor[Any]']]:
     conn = psycopg.connect(**kwargs)
     with conn.cursor() as cur:
         yield cur

patroni/postgresql/misc.py

@@ -2,7 +2,9 @@ import errno
 import logging
 import os
 
-from patroni.exceptions import PostgresException
+from typing import Iterable, Tuple
+
+from ..exceptions import PostgresException
 
 logger = logging.getLogger(__name__)
 
@@ -55,29 +57,27 @@ def postgres_major_version_to_int(pg_version: str) -> int:
     return postgres_version_to_int(pg_version + '.0')
 
 
-def parse_lsn(lsn):
+def parse_lsn(lsn: str) -> int:
     t = lsn.split('/')
     return int(t[0], 16) * 0x100000000 + int(t[1], 16)
 
 
-def parse_history(data):
+def parse_history(data: str) -> Iterable[Tuple[int, int, str]]:
     for line in data.split('\n'):
         values = line.strip().split('\t')
         if len(values) == 3:
             try:
-                values[0] = int(values[0])
-                values[1] = parse_lsn(values[1])
-                yield values
+                yield int(values[0]), parse_lsn(values[1]), values[2]
             except (IndexError, ValueError):
                 logger.exception('Exception when parsing timeline history line "%s"', values)
 
 
-def format_lsn(lsn, full=False):
+def format_lsn(lsn: int, full: bool = False) -> str:
     template = '{0:X}/{1:08X}' if full else '{0:X}/{1:X}'
     return template.format(lsn >> 32, lsn & 0xFFFFFFFF)
 
 
-def fsync_dir(path):
+def fsync_dir(path: str) -> None:
     if os.name != 'nt':
         fd = os.open(path, os.O_DIRECTORY)
         try:

patroni/postgresql/postmaster.py

@@ -7,6 +7,9 @@ import signal
 import subprocess
 import sys
 
+from multiprocessing.connection import Connection
+from typing import Dict, Optional, List
+
 from patroni import PATRONI_ENV_PREFIX, KUBERNETES_ENV_PREFIX
 
 # avoid spawning the resource tracker process
@@ -26,7 +29,7 @@ STOP_SIGNALS = {
 }
 
 
-def pg_ctl_start(conn, cmdline, env):
+def pg_ctl_start(conn: Connection, cmdline: List[str], env: Dict[str, str]) -> None:
     if os.name != 'nt':
         os.setsid()
     try:
@@ -40,7 +43,8 @@ def pg_ctl_start(conn, cmdline, env):
 
 class PostmasterProcess(psutil.Process):
 
-    def __init__(self, pid):
+    def __init__(self, pid: int) -> None:
+        self._postmaster_pid: Dict[str, str]
         self.is_single_user = False
         if pid < 0:
             pid = -pid
@@ -48,7 +52,7 @@ class PostmasterProcess(psutil.Process):
         super(PostmasterProcess, self).__init__(pid)
 
     @staticmethod
-    def _read_postmaster_pidfile(data_dir):
+    def _read_postmaster_pidfile(data_dir: str) -> Dict[str, str]:
         """Reads and parses postmaster.pid from the data directory
 
         :returns dictionary of values if successful, empty dictionary otherwise
@@ -60,7 +64,7 @@ class PostmasterProcess(psutil.Process):
         except IOError:
             return {}
 
-    def _is_postmaster_process(self):
+    def _is_postmaster_process(self) -> bool:
         try:
             start_time = int(self._postmaster_pid.get('start_time', 0))
             if start_time and abs(self.create_time() - start_time) > 3:
@@ -79,7 +83,7 @@ class PostmasterProcess(psutil.Process):
         return True
 
     @classmethod
-    def _from_pidfile(cls, data_dir):
+    def _from_pidfile(cls, data_dir: str) -> Optional['PostmasterProcess']:
         postmaster_pid = PostmasterProcess._read_postmaster_pidfile(data_dir)
         try:
             pid = int(postmaster_pid.get('pid', 0))
@@ -88,10 +92,10 @@ class PostmasterProcess(psutil.Process):
                 proc._postmaster_pid = postmaster_pid
                 return proc
         except ValueError:
-            pass
+            return None
 
     @staticmethod
-    def from_pidfile(data_dir):
+    def from_pidfile(data_dir: str) -> Optional['PostmasterProcess']:
         try:
             proc = PostmasterProcess._from_pidfile(data_dir)
             return proc if proc and proc._is_postmaster_process() else None
@@ -99,13 +103,13 @@ class PostmasterProcess(psutil.Process):
             return None
 
     @classmethod
-    def from_pid(cls, pid):
+    def from_pid(cls, pid: int) -> Optional['PostmasterProcess']:
         try:
             return cls(pid)
         except psutil.NoSuchProcess:
             return None
 
-    def signal_kill(self):
+    def signal_kill(self) -> bool:
         """to suspend and kill postmaster and all children
 
         :returns True if postmaster and children are killed, False if error
@@ -141,7 +145,7 @@ class PostmasterProcess(psutil.Process):
         psutil.wait_procs(children + [self])
         return True
 
-    def signal_stop(self, mode, pg_ctl='pg_ctl'):
+    def signal_stop(self, mode: str, pg_ctl: str = 'pg_ctl') -> Optional[bool]:
         """Signal postmaster process to stop
 
         :returns None if signaled, True if process is already gone, False if error
@@ -161,7 +165,7 @@ class PostmasterProcess(psutil.Process):
 
         return None
 
-    def pg_ctl_kill(self, mode, pg_ctl):
+    def pg_ctl_kill(self, mode: str, pg_ctl: str) -> Optional[bool]:
         try:
             status = subprocess.call([pg_ctl, "kill", STOP_SIGNALS[mode], str(self.pid)])
         except OSError:
@@ -171,7 +175,7 @@ class PostmasterProcess(psutil.Process):
         else:
             return not self.is_running()
 
-    def wait_for_user_backends_to_close(self, stop_timeout):
+    def wait_for_user_backends_to_close(self, stop_timeout: Optional[float]) -> None:
         # These regexps are cross checked against versions PostgreSQL 9.1 .. 15
         aux_proc_re = re.compile("(?:postgres:)( .*:)? (?:(?:archiver|startup|autovacuum launcher|autovacuum worker|"
                                  "checkpointer|logger|stats collector|wal receiver|wal writer|writer)(?: process  )?|"
@@ -183,8 +187,8 @@ class PostmasterProcess(psutil.Process):
         except psutil.Error:
             return logger.debug('Failed to get list of postmaster children')
 
-        user_backends = []
-        user_backends_cmdlines = {}
+        user_backends: List[psutil.Process] = []
+        user_backends_cmdlines: Dict[int, str] = {}
         for child in children:
             try:
                 cmdline = child.cmdline()
@@ -195,7 +199,7 @@ class PostmasterProcess(psutil.Process):
                 pass
         if user_backends:
             logger.debug('Waiting for user backends %s to close', ', '.join(user_backends_cmdlines.values()))
-            gone, live = psutil.wait_procs(user_backends, stop_timeout)
+            _, live = psutil.wait_procs(user_backends, stop_timeout)
             if stop_timeout and live:
                 live = [user_backends_cmdlines[b.pid] for b in live]
                 logger.warning('Backends still alive after %s: %s', stop_timeout, ', '.join(live))
@@ -203,7 +207,7 @@ class PostmasterProcess(psutil.Process):
                 logger.debug("Backends closed")
 
     @staticmethod
-    def start(pgcommand, data_dir, conf, options):
+    def start(pgcommand: str, data_dir: str, conf: str, options: List[str]) -> Optional['PostmasterProcess']:
         # Unfortunately `pg_ctl start` does not return postmaster pid to us. Without this information
         # it is hard to know the current state of postgres startup, so we had to reimplement pg_ctl start
         # in python. It will start postgres, wait for port to be open and wait until postgres will start
@@ -234,7 +238,7 @@ class PostmasterProcess(psutil.Process):
             pass
         cmdline = [pgcommand, '-D', data_dir, '--config-file={}'.format(conf)] + options
         logger.debug("Starting postgres: %s", " ".join(cmdline))
-        ctx = multiprocessing.get_context('spawn') if sys.version_info >= (3, 4) else multiprocessing
+        ctx = multiprocessing.get_context('spawn')
         parent_conn, child_conn = ctx.Pipe(False)
         proc = ctx.Process(target=pg_ctl_start, args=(child_conn, cmdline, env))
         proc.start()

patroni/postgresql/rewind.py

@@ -5,36 +5,46 @@ import shlex
 import shutil
 import subprocess
 
+from enum import IntEnum
 from threading import Lock, Thread
+from typing import Any, Callable, Dict, List, Optional, Union, Tuple
 
+from . import Postgresql
 from .connection import get_connection_cursor
 from .misc import format_lsn, fsync_dir, parse_history, parse_lsn
 from ..async_executor import CriticalTask
-from ..dcs import Leader
+from ..dcs import Leader, RemoteMember
 
 logger = logging.getLogger(__name__)
 
-REWIND_STATUS = type('Enum', (), {'INITIAL': 0, 'CHECKPOINT': 1, 'CHECK': 2, 'NEED': 3,
-                                  'NOT_NEED': 4, 'SUCCESS': 5, 'FAILED': 6})
+
+class REWIND_STATUS(IntEnum):
+    INITIAL = 0
+    CHECKPOINT = 1
+    CHECK = 2
+    NEED = 3
+    NOT_NEED = 4
+    SUCCESS = 5
+    FAILED = 6
 
 
 class Rewind(object):
 
-    def __init__(self, postgresql):
+    def __init__(self, postgresql: Postgresql) -> None:
         self._postgresql = postgresql
         self._checkpoint_task_lock = Lock()
         self.reset_state()
 
     @staticmethod
-    def configuration_allows_rewind(data):
+    def configuration_allows_rewind(data: Dict[str, str]) -> bool:
         return data.get('wal_log_hints setting', 'off') == 'on' or data.get('Data page checksum version', '0') != '0'
 
     @property
-    def enabled(self):
-        return self._postgresql.config.get('use_pg_rewind')
+    def enabled(self) -> bool:
+        return bool(self._postgresql.config.get('use_pg_rewind'))
 
     @property
-    def can_rewind(self):
+    def can_rewind(self) -> bool:
         """ check if pg_rewind executable is there and that pg_controldata indicates
             we have either wal_log_hints or checksums turned on
         """
@@ -52,43 +62,45 @@ class Rewind(object):
         return self.configuration_allows_rewind(self._postgresql.controldata())
 
     @property
-    def should_remove_data_directory_on_diverged_timelines(self):
-        return self._postgresql.config.get('remove_data_directory_on_diverged_timelines')
+    def should_remove_data_directory_on_diverged_timelines(self) -> bool:
+        return bool(self._postgresql.config.get('remove_data_directory_on_diverged_timelines'))
 
     @property
-    def can_rewind_or_reinitialize_allowed(self):
+    def can_rewind_or_reinitialize_allowed(self) -> bool:
         return self.should_remove_data_directory_on_diverged_timelines or self.can_rewind
 
-    def trigger_check_diverged_lsn(self):
+    def trigger_check_diverged_lsn(self) -> None:
         if self.can_rewind_or_reinitialize_allowed and self._state != REWIND_STATUS.NEED:
             self._state = REWIND_STATUS.CHECK
 
     @staticmethod
-    def check_leader_is_not_in_recovery(conn_kwargs):
+    def check_leader_is_not_in_recovery(conn_kwargs: Dict[str, Any]) -> Optional[bool]:
         try:
             with get_connection_cursor(connect_timeout=3, options='-c statement_timeout=2000', **conn_kwargs) as cur:
                 cur.execute('SELECT pg_catalog.pg_is_in_recovery()')
-                if not cur.fetchone()[0]:
+                row = cur.fetchone()
+                if not row or not row[0]:
                     return True
                 logger.info('Leader is still in_recovery and therefore can\'t be used for rewind')
         except Exception:
             return logger.exception('Exception when working with leader')
 
     @staticmethod
-    def check_leader_has_run_checkpoint(conn_kwargs):
+    def check_leader_has_run_checkpoint(conn_kwargs: Dict[str, Any]) -> Optional[str]:
         try:
             with get_connection_cursor(connect_timeout=3, options='-c statement_timeout=2000', **conn_kwargs) as cur:
-                cur.execute("SELECT NOT pg_catalog.pg_is_in_recovery()" +
-                            " AND ('x' || pg_catalog.substr(pg_catalog.pg_walfile_name(" +
-                            " pg_catalog.pg_current_wal_lsn()), 1, 8))::bit(32)::int = timeline_id" +
+                cur.execute("SELECT NOT pg_catalog.pg_is_in_recovery()"
+                            " AND ('x' || pg_catalog.substr(pg_catalog.pg_walfile_name("
+                            " pg_catalog.pg_current_wal_lsn()), 1, 8))::bit(32)::int = timeline_id"
                             " FROM pg_catalog.pg_control_checkpoint()")
-                if not cur.fetchone()[0]:
+                row = cur.fetchone()
+                if not row or not row[0]:
                     return 'leader has not run a checkpoint yet'
         except Exception:
             logger.exception('Exception when working with leader')
             return 'not accessible or not healty'
 
-    def _get_checkpoint_end(self, timeline, lsn):
+    def _get_checkpoint_end(self, timeline: int, lsn: int) -> int:
         """The checkpoint record size in WAL depends on postgres major version and platform (memory alignment).
         Hence, the only reliable way to figure out where it ends, read the record from file with the help of pg_waldump
         and parse the output. We are trying to read two records, and expect that it will fail to read the second one:
@@ -96,12 +108,12 @@ class Rewind(object):
         The error message contains information about LSN of the next record, which is exactly where checkpoint ends."""
 
         lsn8 = format_lsn(lsn, True)
-        lsn = format_lsn(lsn)
-        out, err = self._postgresql.waldump(timeline, lsn, 2)
+        lsn_str = format_lsn(lsn)
+        out, err = self._postgresql.waldump(timeline, lsn_str, 2)
         if out is not None and err is not None:
             out = out.decode('utf-8').rstrip().split('\n')
             err = err.decode('utf-8').rstrip().split('\n')
-            pattern = 'error in WAL record at {0}: invalid record length at '.format(lsn)
+            pattern = 'error in WAL record at {0}: invalid record length at '.format(lsn_str)
 
             if len(out) == 1 and len(err) == 1 and ', lsn: {0}, prev '.format(lsn8) in out[0] and pattern in err[0]:
                 i = err[0].find(pattern) + len(pattern)
@@ -117,20 +129,20 @@ class Rewind(object):
 
         return 0
 
-    def _get_local_timeline_lsn_from_controldata(self):
+    def _get_local_timeline_lsn_from_controldata(self) -> Tuple[Optional[bool], Optional[int], Optional[int]]:
         in_recovery = timeline = lsn = None
         data = self._postgresql.controldata()
         try:
             if data.get('Database cluster state') in ('shut down in recovery', 'in archive recovery'):
                 in_recovery = True
                 lsn = data.get('Minimum recovery ending location')
-                timeline = int(data.get("Min recovery ending loc's timeline"))
+                timeline = int(data.get("Min recovery ending loc's timeline", ""))
                 if lsn == '0/0' or timeline == 0:  # it was a primary when it crashed
                     data['Database cluster state'] = 'shut down'
             if data.get('Database cluster state') == 'shut down':
                 in_recovery = False
                 lsn = data.get('Latest checkpoint location')
-                timeline = int(data.get("Latest checkpoint's TimeLineID"))
+                timeline = int(data.get("Latest checkpoint's TimeLineID", ""))
         except (TypeError, ValueError):
             logger.exception('Failed to get local timeline and lsn from pg_controldata output')
 
@@ -143,10 +155,10 @@ class Rewind(object):
 
         return in_recovery, timeline, lsn
 
-    def _get_local_timeline_lsn(self):
+    def _get_local_timeline_lsn(self) -> Tuple[Optional[bool], Optional[int], Optional[int]]:
         if self._postgresql.is_running():  # if postgres is running - get timeline from replication connection
             in_recovery = True
-            timeline = self._postgresql.received_timeline() or self._postgresql.get_replica_timeline()
+            timeline = self._postgresql.get_replica_timeline()
             lsn = self._postgresql.replayed_location()
         else:  # otherwise analyze pg_controldata output
             in_recovery, timeline, lsn = self._get_local_timeline_lsn_from_controldata()
@@ -156,14 +168,15 @@ class Rewind(object):
         return in_recovery, timeline, lsn
 
     @staticmethod
-    def _log_primary_history(history, i):
+    def _log_primary_history(history: List[Tuple[int, int, str]], i: int) -> None:
         start = max(0, i - 3)
         end = None if i + 4 >= len(history) else i + 2
-        history_show = []
+        history_show: List[str] = []
 
-        def format_history_line(line):
+        def format_history_line(line: Tuple[int, int, str]) -> str:
             return '{0}\t{1}\t{2}'.format(line[0], format_lsn(line[1]), line[2])
 
+        line = None
         for line in history[start:end]:
             history_show.append(format_history_line(line))
 
@@ -173,7 +186,7 @@ class Rewind(object):
 
         logger.info('primary: history=%s', '\n'.join(history_show))
 
-    def _conn_kwargs(self, member, auth):
+    def _conn_kwargs(self, member: Union[Leader, RemoteMember], auth: Dict[str, Any]) -> Dict[str, Any]:
         ret = member.conn_kwargs(auth)
         if not ret.get('dbname'):
             ret['dbname'] = self._postgresql.database
@@ -183,7 +196,7 @@ class Rewind(object):
             ret['target_session_attrs'] = 'read-write'
         return ret
 
-    def _check_timeline_and_lsn(self, leader):
+    def _check_timeline_and_lsn(self, leader: Union[Leader, RemoteMember]) -> None:
         in_recovery, local_timeline, local_lsn = self._get_local_timeline_lsn()
         if local_timeline is None or local_lsn is None:
             return
@@ -205,23 +218,28 @@ class Rewind(object):
         try:
             with self._postgresql.get_replication_connection_cursor(**leader.conn_kwargs()) as cur:
                 cur.execute('IDENTIFY_SYSTEM')
-                primary_timeline = cur.fetchone()[1]
-                logger.info('primary_timeline=%s', primary_timeline)
-                if local_timeline > primary_timeline:  # Not always supported by pg_rewind
-                    need_rewind = True
-                elif local_timeline == primary_timeline:
-                    need_rewind = False
-                elif primary_timeline > 1:
-                    cur.execute('TIMELINE_HISTORY {0}'.format(primary_timeline))
-                    history = cur.fetchone()[1]
-                    if not isinstance(history, str):
-                        history = bytes(history).decode('utf-8')
-                    logger.debug('primary: history=%s', history)
+                row = cur.fetchone()
+                if row:
+                    primary_timeline = row[1]
+                    logger.info('primary_timeline=%s', primary_timeline)
+                    if local_timeline > primary_timeline:  # Not always supported by pg_rewind
+                        need_rewind = True
+                    elif local_timeline == primary_timeline:
+                        need_rewind = False
+                    elif primary_timeline > 1:
+                        cur.execute('TIMELINE_HISTORY {0}'.format(primary_timeline).encode('utf-8'))
+                        row = cur.fetchone()
+                        if row:
+                            history = row[1]
+                            if not isinstance(history, str):
+                                history = bytes(history).decode('utf-8')
+                            logger.debug('primary: history=%s', history)
         except Exception:
             return logger.exception('Exception when working with primary via replication connection')
 
         if history is not None:
             history = list(parse_history(history))
+            i = len(history)
             for i, (parent_timeline, switchpoint, _) in enumerate(history):
                 if parent_timeline == local_timeline:
                     # We don't need to rewind when:
@@ -243,12 +261,12 @@ class Rewind(object):
 
         self._state = need_rewind and REWIND_STATUS.NEED or REWIND_STATUS.NOT_NEED
 
-    def rewind_or_reinitialize_needed_and_possible(self, leader):
+    def rewind_or_reinitialize_needed_and_possible(self, leader: Union[Leader, RemoteMember, None]) -> bool:
         if leader and leader.name != self._postgresql.name and leader.conn_url and self._state == REWIND_STATUS.CHECK:
             self._check_timeline_and_lsn(leader)
-        return leader and leader.conn_url and self._state == REWIND_STATUS.NEED
+        return bool(leader and leader.conn_url) and self._state == REWIND_STATUS.NEED
 
-    def __checkpoint(self, task, wakeup):
+    def __checkpoint(self, task: CriticalTask, wakeup: Callable[..., Any]) -> None:
         try:
             result = self._postgresql.checkpoint()
         except Exception as e:
@@ -258,11 +276,11 @@ class Rewind(object):
             if task.result:
                 wakeup()
 
-    def ensure_checkpoint_after_promote(self, wakeup):
+    def ensure_checkpoint_after_promote(self, wakeup: Callable[..., Any]) -> None:
         """After promote issue a CHECKPOINT from a new thread and asynchronously check the result.
         In case if CHECKPOINT failed, just check that timeline in pg_control was updated."""
 
-        if self._state == REWIND_STATUS.INITIAL and self._postgresql.is_leader():
+        if self._state != REWIND_STATUS.CHECKPOINT and self._postgresql.is_leader():
             with self._checkpoint_task_lock:
                 if self._checkpoint_task:
                     with self._checkpoint_task:
@@ -275,10 +293,10 @@ class Rewind(object):
                     self._checkpoint_task = CriticalTask()
                     Thread(target=self.__checkpoint, args=(self._checkpoint_task, wakeup)).start()
 
-    def checkpoint_after_promote(self):
+    def checkpoint_after_promote(self) -> bool:
         return self._state == REWIND_STATUS.CHECKPOINT
 
-    def _buid_archiver_command(self, command, wal_filename):
+    def _buid_archiver_command(self, command: str, wal_filename: str) -> str:
         """Replace placeholders in the given archiver command's template.
         Applicable for archive_command and restore_command.
         Can also be used for archive_cleanup_command and recovery_end_command,
@@ -306,13 +324,13 @@ class Rewind(object):
 
         return cmd
 
-    def _fetch_missing_wal(self, restore_command, wal_filename):
+    def _fetch_missing_wal(self, restore_command: str, wal_filename: str) -> bool:
         cmd = self._buid_archiver_command(restore_command, wal_filename)
 
         logger.info('Trying to fetch the missing wal: %s', cmd)
         return self._postgresql.cancellable.call(shlex.split(cmd)) == 0
 
-    def _find_missing_wal(self, data):
+    def _find_missing_wal(self, data: bytes) -> Optional[str]:
         # could not open file "$PGDATA/pg_wal/0000000A00006AA100000068": No such file or directory
         pattern = 'could not open file "'
         for line in data.decode('utf-8').split('\n'):
@@ -325,7 +343,7 @@ class Rewind(object):
                     if waldir.endswith('/pg_' + self._postgresql.wal_name) and len(wal_filename) == 24:
                         return wal_filename
 
-    def _archive_ready_wals(self):
+    def _archive_ready_wals(self) -> None:
         """Try to archive WALs that have .ready files just in case
         archive_mode was not set to 'always' before promote, while
         after it the WALs were recycled on the promoted replica.
@@ -352,7 +370,7 @@ class Rewind(object):
                 # it is the author of archive_command, who is responsible
                 # for not overriding the WALs already present in archive
                 logger.info('Trying to archive %s: %s', wal, cmd)
-                if self._postgresql.cancellable.call(shlex.split(cmd)) == 0:
+                if self._postgresql.cancellable.call([cmd], shell=True) == 0:
                     new_name = os.path.join(status_dir, wal + '.done')
                     try:
                         shutil.move(old_name, new_name)
@@ -361,7 +379,7 @@ class Rewind(object):
                 else:
                     logger.info('Failed to archive WAL segment %s', wal)
 
-    def _maybe_clean_pg_replslot(self):
+    def _maybe_clean_pg_replslot(self) -> None:
         """Clean pg_replslot directory if pg version is less then 11
         (pg_rewind deletes $PGDATA/pg_replslot content only since pg11)."""
         if self._postgresql.major_version < 110000:
@@ -373,32 +391,33 @@ class Rewind(object):
             except Exception as e:
                 logger.warning('Unable to clean %s: %r', replslot_dir, e)
 
-    def pg_rewind(self, r):
+    def pg_rewind(self, r: Dict[str, Any]) -> bool:
         # prepare pg_rewind connection
         env = self._postgresql.config.write_pgpass(r)
         env.update(LANG='C', LC_ALL='C', PGOPTIONS='-c statement_timeout=0')
         dsn = self._postgresql.config.format_dsn(r, True)
         logger.info('running pg_rewind from %s', dsn)
 
-        restore_command = self._postgresql.config.get('recovery_conf', {}).get('restore_command') \
+        restore_command = (self._postgresql.config.get('recovery_conf') or {}).get('restore_command') \
             if self._postgresql.major_version < 120000 else self._postgresql.get_guc_value('restore_command')
 
         # Until v15 pg_rewind expected postgresql.conf to be inside $PGDATA, which is not the case on e.g. Debian
-        pg_rewind_can_restore = restore_command and (self._postgresql.major_version >= 150000 or
-                                                     (self._postgresql.major_version >= 130000 and
-                                                      self._postgresql.config._config_dir == self._postgresql.data_dir))
+        pg_rewind_can_restore = restore_command and (self._postgresql.major_version >= 150000
+                                                     or (self._postgresql.major_version >= 130000
+                                                         and self._postgresql.config.config_dir
+                                                         == self._postgresql.data_dir))
 
         cmd = [self._postgresql.pgcommand('pg_rewind')]
         if pg_rewind_can_restore:
             cmd.append('--restore-target-wal')
             if self._postgresql.major_version >= 150000 and\
-                    self._postgresql.config._config_dir != self._postgresql.data_dir:
+                    self._postgresql.config.config_dir != self._postgresql.data_dir:
                 cmd.append('--config-file={0}'.format(self._postgresql.config.postgresql_conf))
 
         cmd.extend(['-D', self._postgresql.data_dir, '--source-server', dsn])
 
         while True:
-            results = {}
+            results: Dict[str, bytes] = {}
             ret = self._postgresql.cancellable.call(cmd, env=env, communicate=results)
 
             logger.info('pg_rewind exit code=%s', ret)
@@ -421,7 +440,7 @@ class Rewind(object):
                 logger.info('Failed to fetch WAL segment %s required for pg_rewind', missing_wal)
                 return False
 
-    def execute(self, leader):
+    def execute(self, leader: Union[Leader, RemoteMember]) -> Optional[bool]:
         if self._postgresql.is_running() and not self._postgresql.stop(checkpoint=False):
             return logger.warning('Can not run pg_rewind because postgres is still running')
 
@@ -439,7 +458,7 @@ class Rewind(object):
             # superuser credentials match rewind_credentials if the latter are not provided or we run 10 or older
             if self._postgresql.config.superuser == self._postgresql.config.rewind_credentials:
                 leader_status = self._postgresql.checkpoint(
-                        self._conn_kwargs(leader, self._postgresql.config.superuser))
+                    self._conn_kwargs(leader, self._postgresql.config.superuser))
             else:  # we run 11+ and have a dedicated pg_rewind user
                 leader_status = self.check_leader_has_run_checkpoint(r)
             if leader_status:  # we tried to run/check for a checkpoint on the remote leader, but it failed
@@ -470,26 +489,26 @@ class Rewind(object):
                         break
         return False
 
-    def reset_state(self):
+    def reset_state(self) -> None:
         self._state = REWIND_STATUS.INITIAL
         with self._checkpoint_task_lock:
             self._checkpoint_task = None
 
     @property
-    def is_needed(self):
+    def is_needed(self) -> bool:
         return self._state in (REWIND_STATUS.CHECK, REWIND_STATUS.NEED)
 
     @property
-    def executed(self):
+    def executed(self) -> bool:
         return self._state > REWIND_STATUS.NOT_NEED
 
     @property
-    def failed(self):
+    def failed(self) -> bool:
         return self._state == REWIND_STATUS.FAILED
 
-    def read_postmaster_opts(self):
+    def read_postmaster_opts(self) -> Dict[str, str]:
         """returns the list of option names/values from postgres.opts, Empty dict if read failed or no file"""
-        result = {}
+        result: Dict[str, str] = {}
         try:
             with open(os.path.join(self._postgresql.data_dir, 'postmaster.opts')) as f:
                 data = f.read()
@@ -501,7 +520,8 @@ class Rewind(object):
             logger.exception('Error when reading postmaster.opts')
         return result
 
-    def single_user_mode(self, communicate=None, options=None):
+    def single_user_mode(self, communicate: Optional[Dict[str, Any]] = None,
+                         options: Optional[Dict[str, str]] = None) -> Optional[int]:
         """run a given command in a single-user mode. If the command is empty - then just start and stop"""
         cmd = [self._postgresql.pgcommand('postgres'), '--single', '-D', self._postgresql.data_dir]
         for opt, val in sorted((options or {}).items()):
@@ -510,7 +530,7 @@ class Rewind(object):
         cmd.append('template1')
         return self._postgresql.cancellable.call(cmd, communicate=communicate)
 
-    def cleanup_archive_status(self):
+    def cleanup_archive_status(self) -> None:
         status_dir = os.path.join(self._postgresql.wal_dir, 'archive_status')
         try:
             for f in os.listdir(status_dir):
@@ -525,7 +545,7 @@ class Rewind(object):
         except OSError:
             logger.exception('Unable to list %s', status_dir)
 
-    def ensure_clean_shutdown(self):
+    def ensure_clean_shutdown(self) -> Optional[bool]:
         self._archive_ready_wals()
         self.cleanup_archive_status()
 
@@ -533,7 +553,7 @@ class Rewind(object):
         opts = self.read_postmaster_opts()
         opts.update({'archive_mode': 'on', 'archive_command': 'false'})
         self._postgresql.config.remove_recovery_conf()
-        output = {}
+        output: Dict[str, bytes] = {}
         ret = self.single_user_mode(communicate=output, options=opts)
         if ret != 0:
             logger.error('Crash recovery finished with code=%s', ret)

patroni/postgresql/slots.py

@@ -1,40 +1,83 @@
+"""Replication slot handling.
+
+Provides classes for the creation, monitoring, management and synchronisation of PostgreSQL replication slots.
+"""
+
 import logging
 import os
 import shutil
-
 from collections import defaultdict
 from contextlib import contextmanager
 from threading import Condition, Thread
+from typing import Any, Dict, Iterator, List, Optional, Union, Tuple, TYPE_CHECKING, Collection
 
 from .connection import get_connection_cursor
 from .misc import format_lsn, fsync_dir
+from ..dcs import Cluster, Leader
+from ..file_perm import pg_perm
 from ..psycopg import OperationalError
 
+if TYPE_CHECKING:  # pragma: no cover
+    from psycopg import Cursor
+    from psycopg2 import cursor
+    from . import Postgresql
+
 logger = logging.getLogger(__name__)
 
 
-def compare_slots(s1, s2, dbid='database'):
-    return s1['type'] == s2['type'] and (s1['type'] == 'physical' or
-                                         s1.get(dbid) == s2.get(dbid) and s1['plugin'] == s2['plugin'])
+def compare_slots(s1: Dict[str, Any], s2: Dict[str, Any], dbid: str = 'database') -> bool:
+    """Compare 2 replication slot objects for equality.
+
+    ..note ::
+        If the first argument is a ``physical`` replication slot then only the `type` of the second slot is compared.
+        If the first argument is another ``type`` (e.g. ``logical``) then *dbid* and ``plugin`` are compared.
+
+    :param s1: First slot dictionary to be compared.
+    :param s2: Second slot dictionary to be compared.
+    :param dbid: Optional attribute to be compared when comparing ``logical`` replication slots.
+
+    :return: ``True`` if the slot ``type`` of *s1* and *s2* is matches, and the ``type`` of *s1* is ``physical``,
+             OR the ``types`` match AND the *dbid* and ``plugin`` attributes are equal.
+
+    """
+    return (s1['type'] == s2['type']
+            and (s1['type'] == 'physical'
+                 or s1.get(dbid) == s2.get(dbid)
+                 and s1['plugin'] == s2['plugin']))
 
 
 class SlotsAdvanceThread(Thread):
+    """Daemon process :class:``Thread`` object for advancing logical replication slots on replicas.
 
-    def __init__(self, slots_handler):
-        super(SlotsAdvanceThread, self).__init__()
+    This ensures that slot advancing queries sent to postgres do not block the main loop.
+    """
+
+    def __init__(self, slots_handler: 'SlotsHandler') -> None:
+        """Create and start a new thread for handling slot advance queries.
+
+        :param slots_handler: The calling class instance for reference to slot information attributes.
+        """
+        super().__init__()
         self.daemon = True
         self._slots_handler = slots_handler
 
         # _copy_slots and _failed are used to asynchronously give some feedback to the main thread
-        self._copy_slots = []
+        self._copy_slots: List[str] = []
         self._failed = False
-
-        self._scheduled = defaultdict(dict)  # {'dbname1': {'slot1': 100, 'slot2': 100}, 'dbname2': {'slot3': 100}}
+        # {'dbname1': {'slot1': 100, 'slot2': 100}, 'dbname2': {'slot3': 100}}
+        self._scheduled: Dict[str, Dict[str, int]] = defaultdict(dict)
         self._condition = Condition()  # protect self._scheduled from concurrent access and to wakeup the run() method
 
         self.start()
 
-    def sync_slot(self, cur, database, slot, lsn):
+    def sync_slot(self, cur: Union['cursor', 'Cursor[Any]'], database: str, slot: str, lsn: int) -> None:
+        """Execute a ``pg_replication_slot_advance`` query and store success for scheduled synchronisation task.
+
+        :param cur: database connection cursor.
+        :param database: name of the database associated with the slot.
+        :param slot: name of the slot to be synchronised.
+        :param lsn: last known LSN position
+        """
         failed = copy = False
         try:
             cur.execute("SELECT pg_catalog.pg_replication_slot_advance(%s, %s)", (slot, format_lsn(lsn)))
@@ -55,7 +98,12 @@ class SlotsAdvanceThread(Thread):
                 if not self._scheduled[database]:
                     self._scheduled.pop(database)
 
-    def sync_slots_in_database(self, database, slots):
+    def sync_slots_in_database(self, database: str, slots: List[str]) -> None:
+        """Synchronise slots for a single database.
+
+        :param database: name of the database.
+        :param slots: list of slot names to synchronise.
+        """
         with self._slots_handler.get_local_connection_cursor(dbname=database, options='-c statement_timeout=0') as cur:
             for slot in slots:
                 with self._condition:
@@ -63,7 +111,8 @@ class SlotsAdvanceThread(Thread):
                 if lsn:
                     self.sync_slot(cur, database, slot, lsn)
 
-    def sync_slots(self):
+    def sync_slots(self) -> None:
+        """Synchronise slots for all scheduled databases."""
         with self._condition:
             databases = list(self._scheduled.keys())
         for database in databases:
@@ -75,7 +124,13 @@ class SlotsAdvanceThread(Thread):
                 except Exception as e:
                     logger.error('Failed to advance replication slots in database %s: %r', database, e)
 
-    def run(self):
+    def run(self) -> None:
+        """Thread main loop entrypoint.
+
+        .. note::
+            Thread will wait until a sync is scheduled from outside, normally triggered during the HA loop or a wakeup
+            call.
+        """
         while True:
             with self._condition:
                 if not self._scheduled:
@@ -83,7 +138,15 @@ class SlotsAdvanceThread(Thread):
 
             self.sync_slots()
 
-    def schedule(self, advance_slots):
+    def schedule(self, advance_slots: Dict[str, Dict[str, int]]) -> Tuple[bool, List[str]]:
+        """Trigger a synchronisation of slots.
+
+        This is the main entrypoint for Patroni HA loop wakeup call.
+
+        :param advance_slots: dictionary containing slots that need to be advanced
+
+        :return: tuple of failure status and a list of slots to be copied
+        """
         with self._condition:
             for database, values in advance_slots.items():
                 self._scheduled[database].update(values)
@@ -94,47 +157,82 @@ class SlotsAdvanceThread(Thread):
 
         return ret
 
-    def on_promote(self):
+    def on_promote(self) -> None:
+        """Reset state of the daemon."""
         with self._condition:
             self._scheduled.clear()
             self._failed = False
             self._copy_slots = []
 
 
-class SlotsHandler(object):
+class SlotsHandler:
+    """Handler for managing and storing information on replication slots in PostgreSQL.
 
-    def __init__(self, postgresql):
+    :ivar pg_replslot_dir: system location path of the PostgreSQL replication slots.
+    :ivar _logical_slots_processing_queue: yet to be processed logical replication slots on the primary
+    """
+
+    def __init__(self, postgresql: 'Postgresql') -> None:
+        """Create an instance with storage attributes for replication slots and schedule the first synchronisation.
+
+        :param postgresql: Calling class instance providing interface to PostgreSQL.
+        """
+        self._force_readiness_check = False
+        self._schedule_load_slots = False
         self._postgresql = postgresql
         self._advance = None
-        self._replication_slots = {}  # already existing replication slots
-        self._unready_logical_slots = {}
+        self._replication_slots: Dict[str, Dict[str, Any]] = {}  # already existing replication slots
+        self._logical_slots_processing_queue: Dict[str, Optional[int]] = {}
         self.pg_replslot_dir = os.path.join(self._postgresql.data_dir, 'pg_replslot')
         self.schedule()
 
-    def _query(self, sql, *params):
+    def _query(self, sql: str, *params: Any) -> Union['cursor', 'Cursor[Any]']:
+        """Helper method for :meth:`Postgresql.query`.
+
+        :param sql: SQL statement to execute.
+        :param params: parameters to pass through to :meth:`Postgresql.query`.
+
+        :returns: query response.
+        """
         return self._postgresql.query(sql, *params, retry=False)
 
     @staticmethod
-    def _copy_items(src, dst, keys=None):
+    def _copy_items(src: Dict[str, Any], dst: Dict[str, Any], keys: Optional[Collection[str]] = None) -> None:
+        """Select values from *src* dictionary to update in *dst* dictionary for optional supplied *keys*.
+
+        :param src: source dictionary that *keys* will be looked up from.
+        :param dst: destination dictionary to be updated.
+        :param keys: optional list of keys to be looked up in the source dictionary.
+        """
         dst.update({key: src[key] for key in keys or ('datoid', 'catalog_xmin', 'confirmed_flush_lsn')})
 
-    def process_permanent_slots(self, slots):
-        """This methods solves three problems at once (I know, it is weird).
+    def process_permanent_slots(self, slots: List[Dict[str, Any]]) -> Dict[str, int]:
+        """Process replication slot information from the host and prepare information used in subsequent cluster tasks.
+
+        .. note::
+            This methods solves three problems.
+
+            The ``cluster_info_query`` from :class:``Postgresql`` is executed every HA loop and returns information
+            about all replication slots that exists on the current host.
+
+            Based on this information perform the following actions:
+
+            1. For the primary we want to expose to DCS permanent logical slots, therefore build (and return) a dict
+               that maps permanent logical slot names to ``confirmed_flush_lsn``.
+            2. detect if one of the previously known permanent slots is missing and schedule resync.
+            3. Update the local cache with the fresh ``catalog_xmin`` and ``confirmed_flush_lsn`` for every known slot.
 
-        The cluster_info_query from `Postgresql` is executed every HA loop and returns
-        information about all replication slots that exists on the current host.
-        Based on this information we perform the following actions:
-        1. For the primary we want to expose to DCS permanent logical slots, therefore the method
-           builds (and returns) a dict, that maps permanent logical slot names and confirmed_flush_lsns.
-        2. This method also detects if one of the previously known permanent slots got missing and schedules resync.
-        3. Updates the local cache with the fresh catalog_xmin and confirmed_flush_lsn for every known slot.
            This info is used when performing the check of logical slot readiness on standbys.
-        """
-        ret = {}
 
-        slots = {slot['slot_name']: slot for slot in slots or []}
-        if slots:
-            for name, value in slots.items():
+        :param slots: replication slot information that exists on the current host.
+
+        :return: dictionary of logical slot names to ``confirmed_flush_lsn``.
+        """
+        ret: Dict[str, int] = {}
+
+        slots_dict: Dict[str, Dict[str, Any]] = {slot['slot_name']: slot for slot in slots or []}
+        if slots_dict:
+            for name, value in slots_dict.items():
                 if name in self._replication_slots:
                     if compare_slots(value, self._replication_slots[name], 'datoid'):
                         if value['type'] == 'logical':
@@ -143,20 +241,30 @@ class SlotsHandler(object):
                     else:
                         self._schedule_load_slots = True
 
-        # It could happen that the slots was deleted in the background, we want to detect this case
-        if any(name not in slots for name in self._replication_slots.keys()):
+        # It could happen that the slot was deleted in the background, we want to detect this case
+        if any(name not in slots_dict for name in self._replication_slots.keys()):
             self._schedule_load_slots = True
 
         return ret
 
-    def load_replication_slots(self):
+    def load_replication_slots(self) -> None:
+        """Query replication slot information from the database and store it for processing by other tasks.
+
+        .. note::
+            Only supported from PostgreSQL version 9.4 onwards.
+
+        Store replication slot ``name``, ``type``, ``plugin``, ``database`` and ``datoid``.
+        If PostgreSQL version is 10 or newer also store ``catalog_xmin`` and ``confirmed_flush_lsn``.
+
+        When using logical slots, store information separately for slot synchronisation  on replica nodes.
+        """
         if self._postgresql.major_version >= 90400 and self._schedule_load_slots:
-            replication_slots = {}
-            extra = ", catalog_xmin, pg_catalog.pg_wal_lsn_diff(confirmed_flush_lsn, '0/0')::bigint"\
+            replication_slots: Dict[str, Dict[str, Any]] = {}
+            extra = ", catalog_xmin, pg_catalog.pg_wal_lsn_diff(confirmed_flush_lsn, '0/0')::bigint" \
                 if self._postgresql.major_version >= 100000 else ""
             skip_temp_slots = ' WHERE NOT temporary' if self._postgresql.major_version >= 100000 else ''
-            cursor = self._query('SELECT slot_name, slot_type, plugin, database, datoid'
-                                 '{0} FROM pg_catalog.pg_replication_slots{1}'.format(extra, skip_temp_slots))
+            cursor = self._query(f'SELECT slot_name, slot_type, plugin, database, datoid'
+                                 f'{extra} FROM pg_catalog.pg_replication_slots{skip_temp_slots}')
             for r in cursor:
                 value = {'type': r[1]}
                 if r[1] == 'logical':
@@ -167,29 +275,64 @@ class SlotsHandler(object):
             self._replication_slots = replication_slots
             self._schedule_load_slots = False
             if self._force_readiness_check:
-                self._unready_logical_slots = {n: None for n, v in replication_slots.items() if v['type'] == 'logical'}
+                self._logical_slots_processing_queue = {n: None for n, v in replication_slots.items()
+                                                        if v['type'] == 'logical'}
                 self._force_readiness_check = False
 
-    def ignore_replication_slot(self, cluster, name):
+    def ignore_replication_slot(self, cluster: Cluster, name: str) -> bool:
+        """Check if slot *name* should not be managed by Patroni.
+
+        :param cluster: cluster state information object.
+        :param name: name of the slot to ignore
+
+        :returns: ``True`` if slot *name* matches any slot specified in ``ignore_slots`` configuration,
+                 otherwise will pass through and return result of :meth:`CitusHandler.ignore_replication_slot`.
+        """
         slot = self._replication_slots[name]
-        for matcher in cluster.config.ignore_slots_matchers:
-            if ((matcher.get("name") is None or matcher["name"] == name)
-               and all(not matcher.get(a) or matcher[a] == slot.get(a) for a in ('database', 'plugin', 'type'))):
-                return True
+        if cluster.config:
+            for matcher in cluster.config.ignore_slots_matchers:
+                if (
+                        (matcher.get("name") is None or matcher["name"] == name)
+                        and all(not matcher.get(a) or matcher[a] == slot.get(a)
+                                for a in ('database', 'plugin', 'type'))
+                ):
+                    return True
         return self._postgresql.citus_handler.ignore_replication_slot(slot)
 
-    def drop_replication_slot(self, name):
-        """Returns a tuple(active, dropped)"""
-        cursor = self._query(('WITH slots AS (SELECT slot_name, active' +
-                              ' FROM pg_catalog.pg_replication_slots WHERE slot_name = %s),' +
-                              ' dropped AS (SELECT pg_catalog.pg_drop_replication_slot(slot_name),' +
-                              ' true AS dropped FROM slots WHERE not active) ' +
-                              'SELECT active, COALESCE(dropped, false) FROM slots' +
-                              ' FULL OUTER JOIN dropped ON true'), name)
-        return cursor.fetchone() if cursor.rowcount == 1 else (False, False)
+    def drop_replication_slot(self, name: str) -> Tuple[bool, bool]:
+        """Drop a named slot from Postgres.
 
-    def _drop_incorrect_slots(self, cluster, slots, paused):
-        # drop old replication slots which are not presented in desired slots
+        :param name: name of the slot to be dropped.
+
+        :returns: a tuple of ``active`` and ``dropped``. ``active`` is ``True`` if the slot is active,
+                  ``dropped`` is ``True`` if the slot was successfully dropped. If the slot was not found return
+                  ``False`` for both.
+        """
+        cursor = self._query(('WITH slots AS (SELECT slot_name, active'
+                              ' FROM pg_catalog.pg_replication_slots WHERE slot_name = %s),'
+                              ' dropped AS (SELECT pg_catalog.pg_drop_replication_slot(slot_name),'
+                              ' true AS dropped FROM slots WHERE not active) '
+                              'SELECT active, COALESCE(dropped, false) FROM slots'
+                              ' FULL OUTER JOIN dropped ON true'), name)
+        row = cursor.fetchone()
+        if not row:
+            row = (False, False)
+        return row[0], row[1]
+
+    def _drop_incorrect_slots(self, cluster: Cluster, slots: Dict[str, Any], paused: bool) -> None:
+        """Compare required slots and configured as permanent slots with those found, dropping extraneous ones.
+
+        .. note::
+            Slots that are not contained in *slots* will be dropped.
+            Slots can be filtered out with ``ignore_slots`` configuration.
+
+            Slots that have matching names but do not match attributes in *slots* will also be dropped.
+
+        :param cluster: cluster state information object.
+        :param slots: dictionary of desired slot names as keys with slot attributes as a dictionary value, if known.
+        :param paused: ``True`` if the patroni cluster is currently in a paused state.
+        """
+        # drop old replication slots which are not presented in desired slots.
         for name in set(self._replication_slots) - set(slots):
             if not paused and not self.ignore_replication_slot(cluster, name):
                 active, dropped = self.drop_replication_slot(name)
@@ -201,6 +344,8 @@ class SlotsHandler(object):
                         logger.debug("Unable to drop unknown replication slot '%s', slot is still active", name)
                     else:
                         logger.error("Failed to drop replication slot '%s'", name)
+
+        # drop slots with matching names but attributes that do not match, e.g. `plugin` or `database`.
         for name, value in slots.items():
             if name in self._replication_slots and not compare_slots(value, self._replication_slots[name]):
                 logger.info("Trying to drop replication slot '%s' because value is changing from %s to %s",
@@ -211,32 +356,58 @@ class SlotsHandler(object):
                     logger.error("Failed to drop replication slot '%s'", name)
                     self._schedule_load_slots = True
 
-    def _ensure_physical_slots(self, slots):
+    def _ensure_physical_slots(self, slots: Dict[str, Any]) -> None:
+        """Create any missing physical replication *slots*.
+
+        Any failures are logged and do not interrupt creation of all *slots*.
+
+        :param slots: A dictionary mapping slot name to slot attributes. This method only considers a slot
+                      if the value is a dictionary with the key ``type`` and a value of ``physical``.
+        """
         immediately_reserve = ', true' if self._postgresql.major_version >= 90600 else ''
         for name, value in slots.items():
             if name not in self._replication_slots and value['type'] == 'physical':
                 try:
-                    self._query(("SELECT pg_catalog.pg_create_physical_replication_slot(%s{0})" +
-                                 " WHERE NOT EXISTS (SELECT 1 FROM pg_catalog.pg_replication_slots" +
-                                 " WHERE slot_type = 'physical' AND slot_name = %s)").format(
-                                     immediately_reserve), name, name)
+                    self._query(f"SELECT pg_catalog.pg_create_physical_replication_slot(%s{immediately_reserve})"
+                                f" WHERE NOT EXISTS (SELECT 1 FROM pg_catalog.pg_replication_slots"
+                                f" WHERE slot_type = 'physical' AND slot_name = %s)",
+                                name, name)
                 except Exception:
                     logger.exception("Failed to create physical replication slot '%s'", name)
                 self._schedule_load_slots = True
 
     @contextmanager
-    def get_local_connection_cursor(self, **kwargs):
+    def get_local_connection_cursor(self, **kwargs: Any) -> Iterator[Union['cursor', 'Cursor[Any]']]:
+        """Create a new database connection to local server.
+
+        Create a non-blocking connection cursor to avoid the situation where an execution of the query of
+        ``pg_replication_slot_advance`` takes longer than the timeout on a HA loop, which could cause a false
+        failure state.
+
+        :param kwargs: Any keyword arguments to pass to :func:`psycopg.connect`.
+
+        :yields: connection cursor object, note implementation varies depending on version of :mod:`psycopg`.
+        """
         conn_kwargs = self._postgresql.config.local_connect_kwargs
         conn_kwargs.update(kwargs)
         with get_connection_cursor(**conn_kwargs) as cur:
             yield cur
 
-    def _ensure_logical_slots_primary(self, slots):
+    def _ensure_logical_slots_primary(self, slots: Dict[str, Any]) -> None:
+        """Create any missing logical replication *slots* on the primary.
+
+        If the logical slot already exists, copy state information into the replication slots structure stored in the
+        class instance.
+
+        :param slots: Slots that should exist are supplied in a dictionary, mapping slot name to any attributes.
+                      The method will only consider slots that have a value that is a dictionary with a key ``type``
+                      with a value that is ``logical``.
+
+        """
         # Group logical slots to be created by database name
-        logical_slots = defaultdict(dict)
+        logical_slots: Dict[str, Dict[str, Dict[str, Any]]] = defaultdict(dict)
         for name, value in slots.items():
             if value['type'] == 'logical':
-                # If the logical already exists, copy some information about it into the original structure
                 if self._replication_slots.get(name, {}).get('datoid'):
                     self._copy_items(self._replication_slots[name], value)
                 else:
@@ -247,8 +418,8 @@ class SlotsHandler(object):
             with self.get_local_connection_cursor(dbname=database) as cur:
                 for name, value in values.items():
                     try:
-                        cur.execute("SELECT pg_catalog.pg_create_logical_replication_slot(%s, %s)" +
-                                    " WHERE NOT EXISTS (SELECT 1 FROM pg_catalog.pg_replication_slots" +
+                        cur.execute("SELECT pg_catalog.pg_create_logical_replication_slot(%s, %s)"
+                                    " WHERE NOT EXISTS (SELECT 1 FROM pg_catalog.pg_replication_slots"
                                     " WHERE slot_type = 'logical' AND slot_name = %s)",
                                     (name, value['plugin'], name))
                     except Exception as e:
@@ -257,51 +428,97 @@ class SlotsHandler(object):
                         slots.pop(name)
                     self._schedule_load_slots = True
 
-    def schedule_advance_slots(self, slots):
+    def schedule_advance_slots(self, slots: Dict[str, Dict[str, int]]) -> Tuple[bool, List[str]]:
+        """Wrapper to ensure slots advance daemon thread is started if not already.
+
+        :param slots: dictionary containing slot information.
+
+        :return: tuple with the result of the scheduling of slot advancement: ``failed`` and list of slots to copy.
+        """
         if not self._advance:
             self._advance = SlotsAdvanceThread(self)
         return self._advance.schedule(slots)
 
-    def _ensure_logical_slots_replica(self, cluster, slots):
-        advance_slots = defaultdict(dict)  # Group logical slots to be advanced by database name
-        create_slots = []  # And collect logical slots to be created on the replica
+    def _ensure_logical_slots_replica(self, cluster: Cluster, slots: Dict[str, Any]) -> List[str]:
+        """Update logical *slots* on replicas.
+
+        If the logical slot already exists, copy state information into the replication slots structure stored in the
+        class instance. Slots that exist are also advanced if their ``confirmed_flush_lsn`` is greater than the stored
+        state of the slot.
+
+        As logical slots can only be created when the primary is available, pass the list of slots that need to be
+        copied back to the caller. They will be created on replicas with :meth:`SlotsHandler.copy_logical_slots`.
+
+        :param cluster: object containing stateful information for the cluster.
+        :param slots: A dictionary mapping slot name to slot attributes. This method only considers a slot
+                      if the value is a dictionary with the key ``type`` and a value of ``logical``.
+
+        :returns: list of slots to be copied from the primary.
+        """
+        # Group logical slots to be advanced by database name
+        advance_slots: Dict[str, Dict[str, int]] = defaultdict(dict)
+        create_slots: List[str] = []  # Collect logical slots to be created on the replica
+
         for name, value in slots.items():
-            if value['type'] == 'logical':
-                # If the logical already exists, copy some information about it into the original structure
-                if self._replication_slots.get(name, {}).get('datoid'):
-                    self._copy_items(self._replication_slots[name], value)
-                    if name in cluster.slots:
-                        try:  # Skip slots that doesn't need to be advanced
-                            if value['confirmed_flush_lsn'] < int(cluster.slots[name]):
-                                advance_slots[value['database']][name] = int(cluster.slots[name])
-                        except Exception as e:
-                            logger.error('Failed to parse "%s": %r', cluster.slots[name], e)
-                elif name in cluster.slots:  # We want to copy only slots with feedback in a DCS
-                    create_slots.append(name)
+            if value['type'] != 'logical':
+                continue
+
+            # If the logical already exists, copy some information about it into the original structure
+            if self._replication_slots.get(name, {}).get('datoid'):
+                self._copy_items(self._replication_slots[name], value)
+                if cluster.slots and name in cluster.slots:
+                    try:  # Skip slots that don't need to be advanced
+                        if value['confirmed_flush_lsn'] < int(cluster.slots[name]):
+                            advance_slots[value['database']][name] = int(cluster.slots[name])
+                    except Exception as e:
+                        logger.error('Failed to parse "%s": %r', cluster.slots[name], e)
+            elif cluster.slots and name in cluster.slots:  # We want to copy only slots with feedback in a DCS
+                create_slots.append(name)
+
+        # Slots to be copied from the primary should be removed from the *slots* structure,
+        # otherwise Patroni falsely assumes that they already exist.
+        for name in create_slots:
+            slots.pop(name)
 
         error, copy_slots = self.schedule_advance_slots(advance_slots)
         if error:
             self._schedule_load_slots = True
         return create_slots + copy_slots
 
-    def sync_replication_slots(self, cluster, nofailover, replicatefrom=None, paused=False):
-        ret = None
-        if self._postgresql.major_version >= 90400 and cluster.config:
+    def sync_replication_slots(self, cluster: Cluster, nofailover: bool,
+                               replicatefrom: Optional[str] = None, paused: bool = False) -> List[str]:
+        """During the HA loop read, check and alter replication slots found in the cluster.
+
+        Read physical and logical slots found on the primary, then compare to those configured in the DCS.
+        Drop any slots that do not match those required by configuration and are not configured as permanent.
+        Create any missing physical slots. If we are the leader then logical slots too, otherwise if logical slots
+        are known and active create them on replica nodes.
+
+        :param cluster: object containing stateful information for the cluster.
+        :param nofailover: ``True`` if this node has been tagged to not be a failover candidate.
+        :param replicatefrom: the tag containing the node to replicate from.
+        :param paused: ``True`` if the cluster is in maintenance mode.
+
+        :returns: list of logical replication slots names that should be copied from the primary.
+        """
+        ret = []
+        if self._postgresql.major_version >= 90400 and self._postgresql.global_config and cluster.config:
             try:
                 self.load_replication_slots()
 
-                slots = cluster.get_replication_slots(self._postgresql.name, self._postgresql.role,
-                                                      nofailover, self._postgresql.major_version, True)
+                slots = cluster.get_replication_slots(
+                    self._postgresql.name, self._postgresql.role, nofailover, self._postgresql.major_version,
+                    is_standby_cluster=self._postgresql.global_config.is_standby_cluster, show_error=True)
 
                 self._drop_incorrect_slots(cluster, slots, paused)
 
                 self._ensure_physical_slots(slots)
 
                 if self._postgresql.is_leader():
-                    self._unready_logical_slots.clear()
+                    self._logical_slots_processing_queue.clear()
                     self._ensure_logical_slots_primary(slots)
                 elif cluster.slots and slots:
-                    self.check_logical_slots_readiness(cluster, nofailover, replicatefrom)
+                    self.check_logical_slots_readiness(cluster, replicatefrom)
 
                     ret = self._ensure_logical_slots_replica(cluster, slots)
 
@@ -312,56 +529,129 @@ class SlotsHandler(object):
         return ret
 
     @contextmanager
-    def _get_leader_connection_cursor(self, leader):
+    def _get_leader_connection_cursor(self, leader: Leader) -> Iterator[Union['cursor', 'Cursor[Any]']]:
+        """Create a new database connection to the leader.
+
+        .. note::
+            Uses rewind user credentials because it has enough permissions to read files from PGDATA.
+            Sets the options ``connect_timeout`` to ``3`` and ``statement_timeout`` to ``2000``.
+
+        :param leader: object with information on the leader
+
+        :yields: connection cursor object, note implementation varies depending on version of ``psycopg``.
+        """
         conn_kwargs = leader.conn_kwargs(self._postgresql.config.rewind_credentials)
         conn_kwargs['dbname'] = self._postgresql.database
         with get_connection_cursor(connect_timeout=3, options="-c statement_timeout=2000", **conn_kwargs) as cur:
             yield cur
 
-    def check_logical_slots_readiness(self, cluster, nofailover, replicatefrom):
-        if self._unready_logical_slots:
+    def check_logical_slots_readiness(self, cluster: Cluster, replicatefrom: Optional[str]) -> bool:
+        """Determine whether all known logical slots are synchronised from the leader.
+
+        1) Retrieve the current ``catalog_xmin`` value for the physical slot from the cluster leader, and
+        2) using previously stored list of "unready" logical slots, those which have yet to be checked hence have no
+           stored slot attributes,
+        3) store logical slot ``catalog_xmin`` when the physical slot ``catalog_xmin`` becomes valid.
+
+        :param cluster: object containing stateful information for the cluster.
+        :param replicatefrom: name of the member that should be used to replicate from.
+
+        :returns: ``False`` if any issue while checking logical slots readiness, ``True`` otherwise.
+        """
+        catalog_xmin = None
+        if self._logical_slots_processing_queue and cluster.leader:
             slot_name = cluster.get_my_slot_name_on_primary(self._postgresql.name, replicatefrom)
             try:
                 with self._get_leader_connection_cursor(cluster.leader) as cur:
                     cur.execute("SELECT slot_name, catalog_xmin FROM pg_catalog.pg_get_replication_slots()"
                                 " WHERE NOT pg_catalog.pg_is_in_recovery() AND slot_name = ANY(%s)",
-                                ([n for n, v in self._unready_logical_slots.items() if v is None] + [slot_name],))
+                                ([n for n, v in self._logical_slots_processing_queue.items()
+                                  if v is None] + [slot_name],))
                     slots = {row[0]: row[1] for row in cur}
                     if slot_name not in slots:
-                        return logger.warning('Physical slot %s does not exist on the primary', slot_name)
+                        logger.warning('Physical slot %s does not exist on the primary', slot_name)
+                        return False
                     catalog_xmin = slots.pop(slot_name)
             except Exception as e:
-                return logger.error("Failed to check %s physical slot on the primary: %r", slot_name, e)
-            # Remember catalog_xmin of logical slots on the primary when catalog_xmin of
-            # the physical slot became valid. Logical slots on replica will be safe to use after
-            # promote when catalog_xmin of the physical slot overtakes these values.
-            if catalog_xmin:
-                for name, value in slots.items():
-                    self._unready_logical_slots[name] = value
-            else:  # Replica isn't streaming or the hot_standby_feedback isn't enabled
-                try:
-                    cur = self._query("SELECT pg_catalog.current_setting('hot_standby_feedback')::boolean")
-                    if not cur.fetchone()[0]:
-                        logger.error('Logical slot failover requires "hot_standby_feedback".'
-                                     ' Please check postgresql.auto.conf')
-                except Exception as e:
-                    logger.error('Failed to check the hot_standby_feedback setting: %r', e)
-                return  # since `catalog_xmin` isn't valid further checks don't make any sense
+                logger.error("Failed to check %s physical slot on the primary: %r", slot_name, e)
+                return False
 
-        for name in list(self._unready_logical_slots):
-            value = self._replication_slots.get(name)
-            # The logical slot on a replica is safe to use when the physical replica slot on the primary:
-            # 1. has a nonzero/non-null catalog_xmin
-            # 2. has a catalog_xmin that is not newer (greater) than the catalog_xmin of any slot on the standby
-            # 3. overtook the catalog_xmin of remembered values of logical slots on the primary.
-            if not value or self._unready_logical_slots[name] <= catalog_xmin <= value['catalog_xmin']:
-                del self._unready_logical_slots[name]
-                if value:
+            if not self._update_pending_logical_slot_primary(slots, catalog_xmin):
+                return False  # since `catalog_xmin` isn't valid further checks don't make any sense
+
+        self._ready_logical_slots(catalog_xmin)
+        return True
+
+    def _update_pending_logical_slot_primary(self, slots: Dict[str, Any], catalog_xmin: Optional[int] = None) -> bool:
+        """Store pending logical slot information for ``catalog_xmin`` on the primary.
+
+        Remember ``catalog_xmin`` of logical slots on the primary when ``catalog_xmin`` of the physical slot became
+        valid. Logical slots on replica will be safe to use after promote when ``catalog_xmin`` of the physical slot
+        overtakes these values.
+
+        :param slots: dictionary of slot information from the primary
+        :param catalog_xmin: ``catalog_xmin`` of the physical slot used by this replica to stream changes from primary.
+
+        :returns: ``False`` if any issue was faced while processing, ``True`` otherwise.
+        """
+        if catalog_xmin is not None:
+            for name, value in slots.items():
+                self._logical_slots_processing_queue[name] = value
+            return True
+
+        # Replica isn't streaming or the hot_standby_feedback isn't enabled
+        try:
+            cur = self._query("SELECT pg_catalog.current_setting('hot_standby_feedback')::boolean")
+            row = cur.fetchone()
+            if row and not row[0]:
+                logger.error('Logical slot failover requires "hot_standby_feedback".'
+                             ' Please check postgresql.auto.conf')
+        except Exception as e:
+            logger.error('Failed to check the hot_standby_feedback setting: %r', e)
+        return False
+
+    def _ready_logical_slots(self, primary_physical_catalog_xmin: Optional[int] = None) -> None:
+        """Ready logical slots by comparing primary physical slot ``catalog_xmin`` to logical ``catalog_xmin``.
+
+        The logical slot on a replica is safe to use when the physical replica slot on the primary:
+
+            1. has a nonzero/non-null ``catalog_xmin`` represented by ``primary_physical_xmin``.
+            2. has a ``catalog_xmin`` that is not newer (greater) than the ``catalog_xmin`` of any slot on the standby
+            3. overtook the ``catalog_xmin`` of remembered values of logical slots on the primary.
+
+        :param primary_physical_catalog_xmin: is the value retrieved from ``pg_catalog.pg_get_replication_slots()`` for
+                                              the physical replication slot on the primary.
+        """
+        # Make a copy of processing queue keys as a list as the queue dictionary is modified inside the loop.
+        for name in list(self._logical_slots_processing_queue):
+            primary_logical_catalog_xmin = self._logical_slots_processing_queue[name]
+            standby_logical_slot = self._replication_slots.get(name, {})
+            standby_logical_catalog_xmin = standby_logical_slot.get('catalog_xmin', 0)
+            if TYPE_CHECKING:  # pragma: no cover
+                assert primary_logical_catalog_xmin is not None
+
+            if (
+                    not standby_logical_slot
+                    or primary_physical_catalog_xmin is not None
+                    and primary_logical_catalog_xmin <= primary_physical_catalog_xmin <= standby_logical_catalog_xmin
+            ):
+
+                del self._logical_slots_processing_queue[name]
+
+                if standby_logical_slot:
                     logger.info('Logical slot %s is safe to be used after a failover', name)
 
-    def copy_logical_slots(self, cluster, create_slots):
+    def copy_logical_slots(self, cluster: Cluster, create_slots: List[str]) -> None:
+        """Create logical replication slots on standby nodes.
+
+        :param cluster: object containing stateful information for the cluster.
+        :param create_slots: list of slot names to copy from the primary.
+        """
         leader = cluster.leader
+        if not leader:
+            return
         slots = cluster.get_replication_slots(self._postgresql.name, 'replica', False, self._postgresql.major_version)
+        copy_slots: Dict[str, Dict[str, Any]] = {}
         with self._get_leader_connection_cursor(leader) as cur:
             try:
                 cur.execute("SELECT slot_name, slot_type, datname, plugin, catalog_xmin, "
@@ -370,48 +660,64 @@ class SlotsHandler(object):
                             " FROM pg_catalog.pg_get_replication_slots() JOIN pg_catalog.pg_database ON datoid = oid"
                             " WHERE NOT pg_catalog.pg_is_in_recovery() AND slot_name = ANY(%s)", (create_slots,))
 
-                create_slots = {}
                 for r in cur:
                     if r[0] in slots:  # slot_name is defined in the global configuration
                         slot = {'type': r[1], 'database': r[2], 'plugin': r[3],
                                 'catalog_xmin': r[4], 'confirmed_flush_lsn': r[5], 'data': r[6]}
                         if compare_slots(slot, slots[r[0]]):
-                            create_slots[r[0]] = slot
+                            copy_slots[r[0]] = slot
                         else:
-                            logger.warning('Will not copy the logical slot "%s" due to the configuration mismatch: ' +
+                            logger.warning('Will not copy the logical slot "%s" due to the configuration mismatch: '
                                            'configuration=%s, slot on the primary=%s', r[0], slots[r[0]], slot)
             except Exception as e:
                 logger.error("Failed to copy logical slots from the %s via postgresql connection: %r", leader.name, e)
 
-        if isinstance(create_slots, dict) and create_slots and self._postgresql.stop():
-            for name, value in create_slots.items():
-                slot_dir = os.path.join(self._postgresql.slots_handler.pg_replslot_dir, name)
+        if copy_slots and self._postgresql.stop():
+            pg_perm.set_permissions_from_data_directory(self._postgresql.data_dir)
+            for name, value in copy_slots.items():
+                slot_dir = os.path.join(self.pg_replslot_dir, name)
                 slot_tmp_dir = slot_dir + '.tmp'
                 if os.path.exists(slot_tmp_dir):
                     shutil.rmtree(slot_tmp_dir)
                 os.makedirs(slot_tmp_dir)
+                os.chmod(slot_tmp_dir, pg_perm.dir_create_mode)
                 fsync_dir(slot_tmp_dir)
-                with open(os.path.join(slot_tmp_dir, 'state'), 'wb') as f:
+                slot_filename = os.path.join(slot_tmp_dir, 'state')
+                with open(slot_filename, 'wb') as f:
+                    os.chmod(slot_filename, pg_perm.file_create_mode)
                     f.write(value['data'])
                     f.flush()
                     os.fsync(f.fileno())
                 if os.path.exists(slot_dir):
                     shutil.rmtree(slot_dir)
                 os.rename(slot_tmp_dir, slot_dir)
+                os.chmod(slot_dir, pg_perm.dir_create_mode)
                 fsync_dir(slot_dir)
-                self._unready_logical_slots[name] = None
-            fsync_dir(self._postgresql.slots_handler.pg_replslot_dir)
+                self._logical_slots_processing_queue[name] = None
+            fsync_dir(self.pg_replslot_dir)
             self._postgresql.start()
 
-    def schedule(self, value=None):
+    def schedule(self, value: Optional[bool] = None) -> None:
+        """Schedule the loading of slot information from the database.
+
+        :param value: the optional value can be used to unschedule if set to ``False`` or force it to be ``True``.
+                      If it is omitted the value will be ``True`` if this PostgreSQL node supports slot replication.
+        """
         if value is None:
             value = self._postgresql.major_version >= 90400
         self._schedule_load_slots = self._force_readiness_check = value
 
-    def on_promote(self):
+    def on_promote(self) -> None:
+        """Entry point from HA cycle used when a standby node is to be promoted to primary.
+
+        .. note::
+            If logical replication slot synchronisation is enabled then slot advancement will be triggered.
+            If any logical slots that were copied are yet to be confirmed as ready a warning message will be logged.
+
+        """
         if self._advance:
             self._advance.on_promote()
 
-        if self._unready_logical_slots:
+        if self._logical_slots_processing_queue:
             logger.warning('Logical replication slots that might be unsafe to use after promote: %s',
-                           set(self._unready_logical_slots))
+                           set(self._logical_slots_processing_queue))

patroni/postgresql/sync.py

@@ -3,9 +3,13 @@ import re
 import time
 
 from copy import deepcopy
+from typing import Collection, List, NamedTuple, Tuple, TYPE_CHECKING
 
-from .validator import CaseInsensitiveDict
+from ..collections import CaseInsensitiveDict, CaseInsensitiveSet
+from ..dcs import Cluster
 from ..psycopg import quote_ident as _quote_ident
+if TYPE_CHECKING:  # pragma: no cover
+    from . import Postgresql
 
 logger = logging.getLogger(__name__)
 
@@ -23,45 +27,59 @@ SYNC_REP_PARSER_RE = re.compile(r"""
          | (?P<parenend> \) )
          | (?P<JUNK> . )
         """, re.X)
-_EMPTY_SSN = {'type': 'off', 'num': 0, 'members': CaseInsensitiveDict({})}
 
 
-def quote_ident(value):
-    """Very simplified version of quote_ident"""
+def quote_ident(value: str) -> str:
+    """Very simplified version of `psycopg` :func:`quote_ident` function."""
     return value if SYNC_STANDBY_NAME_RE.match(value) else _quote_ident(value)
 
 
-def parse_sync_standby_names(value):
-    """Parse postgresql synchronous_standby_names to constituent parts.
-    Returns dict with the following keys:
-    * type: 'quorum'|'priority'
-    * num: int
-    * members: CaseInsensitiveDict, with names as keys
-    * has_star: bool - Present if true
-    If the configuration value can not be parsed, raises a ValueError.
+class _SSN(NamedTuple):
+    """class representing "synchronous_standby_names" value after parsing.
 
-    >>> parse_sync_standby_names('')['type']
+    :ivar sync_type: possible values: 'off', 'priority', 'quorum'
+    :ivar has_star: is set to `True` if "synchronous_standby_names" contains '*'
+    :ivar num: how many nodes are required to be synchronous
+    :ivar members: collection of standby names listed in "synchronous_standby_names"
+    """
+    sync_type: str
+    has_star: bool
+    num: int
+    members: CaseInsensitiveSet
+
+
+_EMPTY_SSN = _SSN('off', False, 0, CaseInsensitiveSet())
+
+
+def parse_sync_standby_names(value: str) -> _SSN:
+    """Parse postgresql synchronous_standby_names to constituent parts.
+
+    :param value: the value of `synchronous_standby_names`
+    :returns: :class:`_SSN` object
+    :raises `ValueError`: if the configuration value can not be parsed
+
+    >>> parse_sync_standby_names('').sync_type
     'off'
 
-    >>> parse_sync_standby_names('FiRsT')['type']
+    >>> parse_sync_standby_names('FiRsT').sync_type
     'priority'
 
-    >>> parse_sync_standby_names('FiRsT')['members']
-    {'FiRsT': True}
-
-    >>> parse_sync_standby_names('"1"')['members']
-    {'1': True}
-
-    >>> parse_sync_standby_names(' a , b ')['members']
-    {'a': True, 'b': True}
-
-    >>> parse_sync_standby_names(' a , b ')['num']
-    1
-
-    >>> parse_sync_standby_names('ANY 4("a",*,b)')['has_star']
+    >>> 'first' in parse_sync_standby_names('FiRsT').members
     True
 
-    >>> parse_sync_standby_names('ANY 4("a",*,b)')['num']
+    >>> set(parse_sync_standby_names('"1"').members)
+    {'1'}
+
+    >>> parse_sync_standby_names(' a , b ').members == {'a', 'b'}
+    True
+
+    >>> parse_sync_standby_names(' a , b ').num
+    1
+
+    >>> parse_sync_standby_names('ANY 4("a",*,b)').has_star
+    True
+
+    >>> parse_sync_standby_names('ANY 4("a",*,b)').num
     4
 
     >>> parse_sync_standby_names('1')  # doctest: +IGNORE_EXCEPTION_DETAIL
@@ -96,18 +114,24 @@ def parse_sync_standby_names(value):
         return deepcopy(_EMPTY_SSN)
 
     if [t[0] for t in tokens[0:3]] == ['any', 'num', 'parenstart'] and tokens[-1][0] == 'parenend':
-        result = {'type': 'quorum', 'num': int(tokens[1][1])}
+        sync_type = 'quorum'
+        num = int(tokens[1][1])
         synclist = tokens[3:-1]
     elif [t[0] for t in tokens[0:3]] == ['first', 'num', 'parenstart'] and tokens[-1][0] == 'parenend':
-        result = {'type': 'priority', 'num': int(tokens[1][1])}
+        sync_type = 'priority'
+        num = int(tokens[1][1])
         synclist = tokens[3:-1]
     elif [t[0] for t in tokens[0:2]] == ['num', 'parenstart'] and tokens[-1][0] == 'parenend':
-        result = {'type': 'priority', 'num': int(tokens[0][1])}
+        sync_type = 'priority'
+        num = int(tokens[0][1])
         synclist = tokens[2:-1]
     else:
-        result = {'type': 'priority', 'num': 1}
+        sync_type = 'priority'
+        num = 1
         synclist = tokens
-    result['members'] = CaseInsensitiveDict({})
+
+    has_star = False
+    members = CaseInsensitiveSet()
     for i, (a_type, a_value, a_pos) in enumerate(synclist):
         if i % 2 == 1:  # odd elements are supposed to be commas
             if len(synclist) == i + 1:  # except the last token
@@ -117,16 +141,82 @@ def parse_sync_standby_names(value):
                 raise ValueError("Unparseable synchronous_standby_names value %r: ""Got token %s %r while"
                                  " expecting comma at %d" % (value, a_type, a_value, a_pos))
         elif a_type in {'ident', 'first', 'any'}:
-            result['members'][a_value] = True
+            members.add(a_value)
         elif a_type == 'star':
-            result['members'][a_value] = True
-            result['has_star'] = True
+            members.add(a_value)
+            has_star = True
         elif a_type == 'dquot':
-            result['members'][a_value[1:-1].replace('""', '"')] = True
+            members.add(a_value[1:-1].replace('""', '"'))
         else:
             raise ValueError("Unparseable synchronous_standby_names value %r: Unexpected token %s %r at %d" %
                              (value, a_type, a_value, a_pos))
-    return result
+    return _SSN(sync_type, has_star, num, members)
+
+
+class _Replica(NamedTuple):
+    """Class representing a single replica that is eligible to be synchronous.
+
+    Attributes are taken from ``pg_stat_replication`` view and respective ``Cluster.members``.
+
+    :ivar pid: PID of walsender process.
+    :ivar application_name: matches with the ``Member.name``.
+    :ivar sync_state: possible values are: ``async``, ``potential``, ``quorum``, and ``sync``.
+    :ivar lsn: ``write_lsn``, ``flush_lsn``, or ``replay_lsn``, depending on the value of ``synchronous_commit`` GUC.
+    :ivar nofailover: whether the corresponding member has ``nofailover`` tag set to ``True``.
+    """
+    pid: int
+    application_name: str
+    sync_state: str
+    lsn: int
+    nofailover: bool
+
+
+class _ReplicaList(List[_Replica]):
+    """A collection of :class:``_Replica`` objects.
+
+    Values are reverse ordered by ``_Replica.sync_state`` and ``_Replica.lsn``.
+    That is, first there will be replicas that have ``sync_state`` == ``sync``, even if they are not
+    the most up-to-date in term of write/flush/replay LSN. It helps to keep the result of chosing new
+    synchronous nodes consistent in case if a synchronous standby member is slowed down OR async node
+    is receiving changes faster than the sync member. Such cases would trigger sync standby member
+    swapping, but only if lag on this member is exceeding a threshold (``maximum_lag_on_syncnode``).
+
+    :ivar max_lsn: maximum value of ``_Replica.lsn`` among all values. In case if there is just one
+                   element in the list we take value of ``pg_current_wal_lsn()``.
+    """
+
+    def __init__(self, postgresql: 'Postgresql', cluster: Cluster) -> None:
+        """Create :class:``_ReplicaList`` object.
+
+        :param postgresql: reference to :class:``Postgresql`` object.
+        :param cluster: currently known cluster state from DCS.
+        """
+        super().__init__()
+
+        # We want to prioritize candidates based on `write_lsn``, ``flush_lsn``, or ``replay_lsn``.
+        # Which column exactly to pick depends on the values of ``synchronous_commit`` GUC.
+        sort_col = {
+            'remote_apply': 'replay',
+            'remote_write': 'write'
+        }.get(postgresql.synchronous_commit(), 'flush') + '_lsn'
+
+        members = CaseInsensitiveDict({m.name: m for m in cluster.members})
+        for row in postgresql.pg_stat_replication():
+            member = members.get(row['application_name'])
+
+            # We want to consider only rows from ``pg_stat_replication` that:
+            # 1. are known to be streaming (write/flush/replay LSN are not NULL).
+            # 2. can be mapped to a ``Member`` of the ``Cluster``:
+            #   a. ``Member`` doesn't have ``nosync`` tag set;
+            #   b. PostgreSQL on the member is known to be running and accepting client connections.
+            if member and row[sort_col] is not None and member.is_running and not member.tags.get('nosync', False):
+                self.append(_Replica(row['pid'], row['application_name'],
+                                     row['sync_state'], row[sort_col], bool(member.nofailover)))
+
+        # Prefer replicas that are in state ``sync`` and with higher values of ``write``/``flush``/``replay`` LSN.
+        self.sort(key=lambda r: (r.sync_state, r.lsn), reverse=True)
+
+        self.max_lsn = max(self, key=lambda x: x.lsn).lsn if len(self) > 1 else postgresql.last_operation()
 
 
 class SyncHandler(object):
@@ -137,7 +227,7 @@ class SyncHandler(object):
     and the `current_state()` method will count newly added names as "sync" only when
     they reached memorized LSN and also reported as "sync" by `pg_stat_replication`"""
 
-    def __init__(self, postgresql):
+    def __init__(self, postgresql: 'Postgresql') -> None:
         self._postgresql = postgresql
         self._synchronous_standby_names = ''  # last known value of synchronous_standby_names
         self._ssn_data = deepcopy(_EMPTY_SSN)
@@ -145,12 +235,15 @@ class SyncHandler(object):
         # "sync" replication connections, that were verified to reach self._primary_flush_lsn at some point
         self._ready_replicas = CaseInsensitiveDict({})  # keys: member names, values: connection pids
 
-    def _handle_synchronous_standby_names_change(self):
-        """If synchronous_standby_names has changed we need to check that newly added replicas
-        have reached self._primary_flush_lsn. Only after that they could be counted as sync."""
+    def _handle_synchronous_standby_names_change(self) -> None:
+        """Handles changes of "synchronous_standby_names" GUC.
+
+        If "synchronous_standby_names" was changed, we need to check that newly added replicas have
+        reached `self._primary_flush_lsn`. Only after that they could be counted as synchronous.
+        """
         synchronous_standby_names = self._postgresql.synchronous_standby_names()
         if synchronous_standby_names == self._synchronous_standby_names:
-            return False
+            return
 
         self._synchronous_standby_names = synchronous_standby_names
         try:
@@ -161,91 +254,92 @@ class SyncHandler(object):
 
         # Invalidate cache of "sync" connections
         for app_name in list(self._ready_replicas.keys()):
-            if app_name not in self._ssn_data['members']:
+            if app_name not in self._ssn_data.members:
                 del self._ready_replicas[app_name]
 
         # Newly connected replicas will be counted as sync only when reached self._primary_flush_lsn
         self._primary_flush_lsn = self._postgresql.last_operation()
-        self._postgresql.query('SELECT pg_catalog.txid_current()')  # Ensure some WAL traffic to move replication
+        # Ensure some WAL traffic to move replication
+        self._postgresql.query("""DO $$
+BEGIN
+    SET local synchronous_commit = 'off';
+    PERFORM * FROM pg_catalog.txid_current();
+END;$$""")
         self._postgresql.reset_cluster_info_state(None)  # Reset internal cache to query fresh values
 
-    def current_state(self, cluster, sync_node_count=1, sync_node_maxlag=-1):
-        """Finds best candidates to be the synchronous standbys.
+    def _process_replica_readiness(self, cluster: Cluster, replica_list: _ReplicaList) -> None:
+        """Flags replicas as truly "synchronous" when they have caught up with ``_primary_flush_lsn``.
+
+        :param cluster: current cluster topology from DCS
+        :param replica_list: collection of replicas that we want to evaluate.
+        """
+        for replica in replica_list:
+            # if standby name is listed in the /sync key we can count it as synchronous, otherwise
+            # it becomes really synchronous when sync_state = 'sync' and it is known that it managed to catch up
+            if replica.application_name not in self._ready_replicas\
+                    and replica.application_name in self._ssn_data.members\
+                    and (cluster.sync.matches(replica.application_name)
+                         or replica.sync_state == 'sync' and replica.lsn >= self._primary_flush_lsn):
+                self._ready_replicas[replica.application_name] = replica.pid
+
+    def current_state(self, cluster: Cluster) -> Tuple[CaseInsensitiveSet, CaseInsensitiveSet]:
+        """Find the best candidates to be the synchronous standbys.
 
         Current synchronous standby is always preferred, unless it has disconnected or does not want to be a
         synchronous standby any longer.
-        Parameter sync_node_maxlag(maximum_lag_on_syncnode) would help swapping unhealthy sync replica in case
-        if it stops responding (or hung). Please set the value high enough so it won't unncessarily swap sync
-        standbys during high loads. Any less or equal of 0 value keep the behavior backward compatible and
-        will not swap. Please note that it will not also swap sync standbys in case where all replicas are hung.
 
-        :returns: tuple of candidates list and synchronous standby list."""
+        Standbys are selected based on values from the global configuration:
 
+        - `maximum_lag_on_syncnode`: would help swapping unhealthy sync replica in case if it stops
+          responding (or hung). Please set the value high enough so it won't unncessarily swap sync
+          standbys during high loads. Any value less or equal of 0 keeps the behavior backward compatible.
+          Please note that it will not also swap sync standbys in case where all replicas are hung.
+        - `synchronous_node_count`: controlls how many nodes should be set as synchronous.
+
+        :returns: tuple of candidates :class:`CaseInsensitiveSet` and synchronous standbys :class:`CaseInsensitiveSet`.
+        """
         self._handle_synchronous_standby_names_change()
 
-        # Pick candidates based on who has higher replay/remote_write/flush lsn.
-        sort_col = {
-            'remote_apply': 'replay',
-            'remote_write': 'write'
-        }.get(self._postgresql.synchronous_commit(), 'flush') + '_lsn'
+        replica_list = _ReplicaList(self._postgresql, cluster)
+        self._process_replica_readiness(cluster, replica_list)
 
-        pg_stat_replication = [(r['pid'], r['application_name'], r['sync_state'], r[sort_col])
-                               for r in self._postgresql.pg_stat_replication()
-                               if r[sort_col] is not None]
+        if TYPE_CHECKING:  # pragma: no cover
+            assert self._postgresql.global_config is not None
+        sync_node_count = self._postgresql.global_config.synchronous_node_count\
+            if self._postgresql.supports_multiple_sync else 1
+        sync_node_maxlag = self._postgresql.global_config.maximum_lag_on_syncnode
 
-        members = CaseInsensitiveDict({m.name: m for m in cluster.members})
-        replica_list = []
-        # pg_stat_replication.sync_state has 4 possible states - async, potential, quorum, sync.
-        # That is, alphabetically they are in the reversed order of priority.
-        # Since we are doing reversed sort on (sync_state, lsn) tuples, it helps to keep the result
-        # consistent in case if a synchronous standby member is slowed down OR async node receiving
-        # changes faster than the sync member (very rare but possible).
-        # Such cases would trigger sync standby member swapping, but only if lag on a sync node exceeding a threshold.
-        for pid, app_name, sync_state, replica_lsn in sorted(pg_stat_replication, key=lambda r: r[2:4], reverse=True):
-            member = members.get(app_name)
-            if member and member.is_running and not member.tags.get('nosync', False):
-                replica_list.append((pid, member.name, sync_state, replica_lsn, bool(member.nofailover)))
-
-        max_lsn = max(replica_list, key=lambda x: x[3])[3]\
-            if len(replica_list) > 1 else self._postgresql.last_operation()
-
-        if self._postgresql.major_version < 90600:
-            sync_node_count = 1
-
-        candidates = []
-        sync_nodes = []
+        candidates = CaseInsensitiveSet()
+        sync_nodes = CaseInsensitiveSet()
         # Prefer members without nofailover tag. We are relying on the fact that sorts are guaranteed to be stable.
-        for pid, app_name, sync_state, replica_lsn, _ in sorted(replica_list, key=lambda x: x[4]):
-            # if standby name is listed in the /sync key we can count it as synchronous, otherwice
-            # ig becomes really synchronous when sync_state = 'sync' and it is known that it managed to catch up
-            if app_name not in self._ready_replicas and app_name in self._ssn_data['members'] and\
-                    (cluster.sync and app_name in cluster.sync.members or
-                     sync_state == 'sync' and replica_lsn >= self._primary_flush_lsn):
-                self._ready_replicas[app_name] = pid
-
-            if sync_node_maxlag <= 0 or max_lsn - replica_lsn <= sync_node_maxlag:
-                candidates.append(app_name)
-                if sync_state == 'sync' and app_name in self._ready_replicas:
-                    sync_nodes.append(app_name)
+        for replica in sorted(replica_list, key=lambda x: x.nofailover):
+            if sync_node_maxlag <= 0 or replica_list.max_lsn - replica.lsn <= sync_node_maxlag:
+                candidates.add(replica.application_name)
+                if replica.sync_state == 'sync' and replica.application_name in self._ready_replicas:
+                    sync_nodes.add(replica.application_name)
             if len(candidates) >= sync_node_count:
                 break
 
         return candidates, sync_nodes
 
-    def set_synchronous_standby_names(self, value):
-        """Constructs and sets `synchronous_standby_names` value.
+    def set_synchronous_standby_names(self, sync: Collection[str]) -> None:
+        """Constructs and sets "synchronous_standby_names" GUC value.
 
-        :param value: list[str] - the list of wanted sync members"""
-        if value and value != ['*']:
-            value = [quote_ident(x) for x in value]
-
-        if self._postgresql.major_version >= 90600 and len(value) > 1:
-            sync_param = '{0} ({1})'.format(len(value), ','.join(value))
+        :param sync: set of nodes to sync to
+        """
+        has_asterisk = '*' in sync
+        if has_asterisk:
+            sync = ['*']
         else:
-            sync_param = next(iter(value), None)
+            sync = [quote_ident(x) for x in sync]
 
-        if not (self._postgresql.config.set_synchronous_standby_names(sync_param) and
-                self._postgresql.state == 'running' and self._postgresql.is_leader()) or value == ['*']:
+        if self._postgresql.supports_multiple_sync and len(sync) > 1:
+            sync_param = '{0} ({1})'.format(len(sync), ','.join(sync))
+        else:
+            sync_param = next(iter(sync), None)
+
+        if not (self._postgresql.config.set_synchronous_standby_names(sync_param)
+                and self._postgresql.state == 'running' and self._postgresql.is_leader()) or has_asterisk:
             return
 
         time.sleep(0.1)  # Usualy it takes 1ms to reload postgresql.conf, but we will give it 100ms
@@ -253,6 +347,6 @@ class SyncHandler(object):
         # Reset internal cache to query fresh values
         self._postgresql.reset_cluster_info_state(None)
 
-        # timeline == 0 -- indicates that this is the replica, shoudn't ever happen
+        # timeline == 0 -- indicates that this is the replica
         if self._postgresql.get_primary_timeline() > 0:
             self._handle_synchronous_standby_names_change()

patroni/postgresql/validator.py

@@ -1,46 +1,87 @@
 import abc
+from copy import deepcopy
 import logging
+import os
+import yaml
 
-from collections import namedtuple
-from urllib3.response import HTTPHeaderDict
+from typing import Any, Dict, Iterator, List, MutableMapping, Optional, Tuple, Type, Union
 
+from ..collections import CaseInsensitiveDict, CaseInsensitiveSet
+from ..exceptions import PatroniException
 from ..utils import parse_bool, parse_int, parse_real
 
 logger = logging.getLogger(__name__)
 
 
-class CaseInsensitiveDict(HTTPHeaderDict):
+class _Transformable(abc.ABC):
 
-    def add(self, key, val):
-        self[key] = val
+    def __init__(self, version_from: int, version_till: Optional[int] = None) -> None:
+        self.__version_from = version_from
+        self.__version_till = version_till
 
-    def __getitem__(self, key):
-        return self._container[key.lower()][1]
+    @classmethod
+    def get_subclasses(cls) -> Iterator[Type['_Transformable']]:
+        """Recursively get all subclasses of :class:`_Transformable`.
 
-    def __repr__(self):
-        return str(dict(self.items()))
+        :yields: each subclass of :class:`_Transformable`.
+        """
+        for subclass in cls.__subclasses__():
+            yield from subclass.get_subclasses()
+            yield subclass
 
-    def copy(self):
-        return CaseInsensitiveDict(self._container.values())
+    @property
+    def version_from(self) -> int:
+        return self.__version_from
+
+    @property
+    def version_till(self) -> Optional[int]:
+        return self.__version_till
+
+    @abc.abstractmethod
+    def transform(self, name: str, value: Any) -> Optional[Any]:
+        """Verify that provided value is valid.
+
+        :param name: GUC's name
+        :param value: GUC's value
+        :returns: the value (sometimes clamped) or ``None`` if the value isn't valid
+        """
 
 
-class Bool(namedtuple('Bool', 'version_from,version_till')):
+class Bool(_Transformable):
 
-    @staticmethod
-    def transform(name, value):
+    def transform(self, name: str, value: Any) -> Optional[Any]:
         if parse_bool(value) is not None:
             return value
         logger.warning('Removing bool parameter=%s from the config due to the invalid value=%s', name, value)
 
 
-class Number(abc.ABC, namedtuple('Number', 'version_from,version_till,min_val,max_val,unit')):
+class Number(_Transformable):
+
+    def __init__(self, *, version_from: int, version_till: Optional[int] = None, min_val: Union[int, float],
+                 max_val: Union[int, float], unit: Optional[str] = None) -> None:
+        super(Number, self).__init__(version_from, version_till)
+        self.__min_val = min_val
+        self.__max_val = max_val
+        self.__unit = unit
+
+    @property
+    def min_val(self) -> Union[int, float]:
+        return self.__min_val
+
+    @property
+    def max_val(self) -> Union[int, float]:
+        return self.__max_val
+
+    @property
+    def unit(self) -> Optional[str]:
+        return self.__unit
 
     @staticmethod
     @abc.abstractmethod
-    def parse(value, unit):
-        """parse value"""
+    def parse(value: Any, unit: Optional[str]) -> Optional[Any]:
+        """Convert provided value to unit."""
 
-    def transform(self, name, value):
+    def transform(self, name: str, value: Any) -> Union[int, float, None]:
         num_value = self.parse(value, self.unit)
         if num_value is not None:
             if num_value < self.min_val:
@@ -59,20 +100,29 @@ class Number(abc.ABC, namedtuple('Number', 'version_from,version_till,min_val,ma
 class Integer(Number):
 
     @staticmethod
-    def parse(value, unit):
+    def parse(value: Any, unit: Optional[str]) -> Optional[int]:
         return parse_int(value, unit)
 
 
 class Real(Number):
 
     @staticmethod
-    def parse(value, unit):
+    def parse(value: Any, unit: Optional[str]) -> Optional[float]:
         return parse_real(value, unit)
 
 
-class Enum(namedtuple('Enum', 'version_from,version_till,possible_values')):
+class Enum(_Transformable):
 
-    def transform(self, name, value):
+    def __init__(self, *, version_from: int, version_till: Optional[int] = None,
+                 possible_values: Tuple[str, ...]) -> None:
+        super(Enum, self).__init__(version_from, version_till)
+        self.__possible_values = possible_values
+
+    @property
+    def possible_values(self) -> Tuple[str, ...]:
+        return self.__possible_values
+
+    def transform(self, name: str, value: Optional[Any]) -> Optional[Any]:
         if str(value).lower() in self.possible_values:
             return value
         logger.warning('Removing enum parameter=%s from the config due to the invalid value=%s', name, value)
@@ -80,469 +130,384 @@ class Enum(namedtuple('Enum', 'version_from,version_till,possible_values')):
 
 class EnumBool(Enum):
 
-    def transform(self, name, value):
+    def transform(self, name: str, value: Optional[Any]) -> Optional[Any]:
         if parse_bool(value) is not None:
             return value
         return super(EnumBool, self).transform(name, value)
 
 
-class String(namedtuple('String', 'version_from,version_till')):
+class String(_Transformable):
 
-    @staticmethod
-    def transform(name, value):
+    def transform(self, name: str, value: Optional[Any]) -> Optional[Any]:
         return value
 
 
 # Format:
-#  key - parameter name
-#  value - tuple or multiple tuples if something was changing in GUC across postgres versions
-parameters = CaseInsensitiveDict({
-    'allow_in_place_tablespaces': Bool(150000, None),
-    'allow_system_table_mods': Bool(90300, None),
-    'application_name': String(90300, None),
-    'archive_command': String(90300, None),
-    'archive_library': String(150000, None),
-    'archive_mode': (
-        Bool(90300, 90500),
-        EnumBool(90500, None, ('always',))
-    ),
-    'archive_timeout': Integer(90300, None, 0, 1073741823, 's'),
-    'array_nulls': Bool(90300, None),
-    'authentication_timeout': Integer(90300, None, 1, 600, 's'),
-    'autovacuum': Bool(90300, None),
-    'autovacuum_analyze_scale_factor': Real(90300, None, 0, 100, None),
-    'autovacuum_analyze_threshold': Integer(90300, None, 0, 2147483647, None),
-    'autovacuum_freeze_max_age': Integer(90300, None, 100000, 2000000000, None),
-    'autovacuum_max_workers': (
-        Integer(90300, 90600, 1, 8388607, None),
-        Integer(90600, None, 1, 262143, None)
-    ),
-    'autovacuum_multixact_freeze_max_age': Integer(90300, None, 10000, 2000000000, None),
-    'autovacuum_naptime': Integer(90300, None, 1, 2147483, 's'),
-    'autovacuum_vacuum_cost_delay': (
-        Integer(90300, 120000, -1, 100, 'ms'),
-        Real(120000, None, -1, 100, 'ms')
-    ),
-    'autovacuum_vacuum_cost_limit': Integer(90300, None, -1, 10000, None),
-    'autovacuum_vacuum_insert_scale_factor': Real(130000, None, 0, 100, None),
-    'autovacuum_vacuum_insert_threshold': Integer(130000, None, -1, 2147483647, None),
-    'autovacuum_vacuum_scale_factor': Real(90300, None, 0, 100, None),
-    'autovacuum_vacuum_threshold': Integer(90300, None, 0, 2147483647, None),
-    'autovacuum_work_mem': Integer(90400, None, -1, 2147483647, 'kB'),
-    'backend_flush_after': Integer(90600, None, 0, 256, '8kB'),
-    'backslash_quote': EnumBool(90300, None, ('safe_encoding',)),
-    'backtrace_functions': String(130000, None),
-    'bgwriter_delay': Integer(90300, None, 10, 10000, 'ms'),
-    'bgwriter_flush_after': Integer(90600, None, 0, 256, '8kB'),
-    'bgwriter_lru_maxpages': (
-        Integer(90300, 100000, 0, 1000, None),
-        Integer(100000, None, 0, 1073741823, None)
-    ),
-    'bgwriter_lru_multiplier': Real(90300, None, 0, 10, None),
-    'bonjour': Bool(90300, None),
-    'bonjour_name': String(90300, None),
-    'bytea_output': Enum(90300, None, ('escape', 'hex')),
-    'check_function_bodies': Bool(90300, None),
-    'checkpoint_completion_target': Real(90300, None, 0, 1, None),
-    'checkpoint_flush_after': Integer(90600, None, 0, 256, '8kB'),
-    'checkpoint_segments': Integer(90300, 90500, 1, 2147483647, None),
-    'checkpoint_timeout': (
-        Integer(90300, 90600, 30, 3600, 's'),
-        Integer(90600, None, 30, 86400, 's')
-    ),
-    'checkpoint_warning': Integer(90300, None, 0, 2147483647, 's'),
-    'client_connection_check_interval': Integer(140000, None, 0, 2147483647, 'ms'),
-    'client_encoding': String(90300, None),
-    'client_min_messages': Enum(90300, None, ('debug5', 'debug4', 'debug3', 'debug2',
-                                              'debug1', 'log', 'notice', 'warning', 'error')),
-    'cluster_name': String(90500, None),
-    'commit_delay': Integer(90300, None, 0, 100000, None),
-    'commit_siblings': Integer(90300, None, 0, 1000, None),
-    'compute_query_id': (
-        EnumBool(140000, 150000, ('auto',)),
-        EnumBool(150000, None, ('auto', 'regress'))
-    ),
-    'config_file': String(90300, None),
-    'constraint_exclusion': EnumBool(90300, None, ('partition',)),
-    'cpu_index_tuple_cost': Real(90300, None, 0, 1.79769e+308, None),
-    'cpu_operator_cost': Real(90300, None, 0, 1.79769e+308, None),
-    'cpu_tuple_cost': Real(90300, None, 0, 1.79769e+308, None),
-    'cursor_tuple_fraction': Real(90300, None, 0, 1, None),
-    'data_directory': String(90300, None),
-    'data_sync_retry': Bool(90400, None),
-    'DateStyle': String(90300, None),
-    'db_user_namespace': Bool(90300, None),
-    'deadlock_timeout': Integer(90300, None, 1, 2147483647, 'ms'),
-    'debug_discard_caches': Integer(150000, None, 0, 0, None),
-    'debug_pretty_print': Bool(90300, None),
-    'debug_print_parse': Bool(90300, None),
-    'debug_print_plan': Bool(90300, None),
-    'debug_print_rewritten': Bool(90300, None),
-    'default_statistics_target': Integer(90300, None, 1, 10000, None),
-    'default_table_access_method': String(120000, None),
-    'default_tablespace': String(90300, None),
-    'default_text_search_config': String(90300, None),
-    'default_toast_compression': Enum(140000, None, ('pglz', 'lz4')),
-    'default_transaction_deferrable': Bool(90300, None),
-    'default_transaction_isolation': Enum(90300, None, ('serializable', 'repeatable read',
-                                                        'read committed', 'read uncommitted')),
-    'default_transaction_read_only': Bool(90300, None),
-    'default_with_oids': Bool(90300, 120000),
-    'dynamic_library_path': String(90300, None),
-    'dynamic_shared_memory_type': (
-        Enum(90400, 120000, ('posix', 'sysv', 'mmap', 'none')),
-        Enum(120000, None, ('posix', 'sysv', 'mmap'))
-    ),
-    'effective_cache_size': Integer(90300, None, 1, 2147483647, '8kB'),
-    'effective_io_concurrency': Integer(90300, None, 0, 1000, None),
-    'enable_async_append': Bool(140000, None),
-    'enable_bitmapscan': Bool(90300, None),
-    'enable_gathermerge': Bool(100000, None),
-    'enable_hashagg': Bool(90300, None),
-    'enable_hashjoin': Bool(90300, None),
-    'enable_incremental_sort': Bool(130000, None),
-    'enable_indexonlyscan': Bool(90300, None),
-    'enable_indexscan': Bool(90300, None),
-    'enable_material': Bool(90300, None),
-    'enable_memoize': Bool(150000, None),
-    'enable_mergejoin': Bool(90300, None),
-    'enable_nestloop': Bool(90300, None),
-    'enable_parallel_append': Bool(110000, None),
-    'enable_parallel_hash': Bool(110000, None),
-    'enable_partition_pruning': Bool(110000, None),
-    'enable_partitionwise_aggregate': Bool(110000, None),
-    'enable_partitionwise_join': Bool(110000, None),
-    'enable_seqscan': Bool(90300, None),
-    'enable_sort': Bool(90300, None),
-    'enable_tidscan': Bool(90300, None),
-    'escape_string_warning': Bool(90300, None),
-    'event_source': String(90300, None),
-    'exit_on_error': Bool(90300, None),
-    'extension_destdir': String(140000, None),
-    'external_pid_file': String(90300, None),
-    'extra_float_digits': Integer(90300, None, -15, 3, None),
-    'force_parallel_mode': EnumBool(90600, None, ('regress',)),
-    'from_collapse_limit': Integer(90300, None, 1, 2147483647, None),
-    'fsync': Bool(90300, None),
-    'full_page_writes': Bool(90300, None),
-    'geqo': Bool(90300, None),
-    'geqo_effort': Integer(90300, None, 1, 10, None),
-    'geqo_generations': Integer(90300, None, 0, 2147483647, None),
-    'geqo_pool_size': Integer(90300, None, 0, 2147483647, None),
-    'geqo_seed': Real(90300, None, 0, 1, None),
-    'geqo_selection_bias': Real(90300, None, 1.5, 2, None),
-    'geqo_threshold': Integer(90300, None, 2, 2147483647, None),
-    'gin_fuzzy_search_limit': Integer(90300, None, 0, 2147483647, None),
-    'gin_pending_list_limit': Integer(90500, None, 64, 2147483647, 'kB'),
-    'hash_mem_multiplier': Real(130000, None, 1, 1000, None),
-    'hba_file': String(90300, None),
-    'hot_standby': Bool(90300, None),
-    'hot_standby_feedback': Bool(90300, None),
-    'huge_pages': EnumBool(90400, None, ('try',)),
-    'huge_page_size': Integer(140000, None, 0, 2147483647, 'kB'),
-    'ident_file': String(90300, None),
-    'idle_in_transaction_session_timeout': Integer(90600, None, 0, 2147483647, 'ms'),
-    'idle_session_timeout': Integer(140000, None, 0, 2147483647, 'ms'),
-    'ignore_checksum_failure': Bool(90300, None),
-    'ignore_invalid_pages': Bool(130000, None),
-    'ignore_system_indexes': Bool(90300, None),
-    'IntervalStyle': Enum(90300, None, ('postgres', 'postgres_verbose', 'sql_standard', 'iso_8601')),
-    'jit': Bool(110000, None),
-    'jit_above_cost': Real(110000, None, -1, 1.79769e+308, None),
-    'jit_debugging_support': Bool(110000, None),
-    'jit_dump_bitcode': Bool(110000, None),
-    'jit_expressions': Bool(110000, None),
-    'jit_inline_above_cost': Real(110000, None, -1, 1.79769e+308, None),
-    'jit_optimize_above_cost': Real(110000, None, -1, 1.79769e+308, None),
-    'jit_profiling_support': Bool(110000, None),
-    'jit_provider': String(110000, None),
-    'jit_tuple_deforming': Bool(110000, None),
-    'join_collapse_limit': Integer(90300, None, 1, 2147483647, None),
-    'krb_caseins_users': Bool(90300, None),
-    'krb_server_keyfile': String(90300, None),
-    'krb_srvname': String(90300, 90400),
-    'lc_messages': String(90300, None),
-    'lc_monetary': String(90300, None),
-    'lc_numeric': String(90300, None),
-    'lc_time': String(90300, None),
-    'listen_addresses': String(90300, None),
-    'local_preload_libraries': String(90300, None),
-    'lock_timeout': Integer(90300, None, 0, 2147483647, 'ms'),
-    'lo_compat_privileges': Bool(90300, None),
-    'log_autovacuum_min_duration': Integer(90300, None, -1, 2147483647, 'ms'),
-    'log_checkpoints': Bool(90300, None),
-    'log_connections': Bool(90300, None),
-    'log_destination': String(90300, None),
-    'log_directory': String(90300, None),
-    'log_disconnections': Bool(90300, None),
-    'log_duration': Bool(90300, None),
-    'log_error_verbosity': Enum(90300, None, ('terse', 'default', 'verbose')),
-    'log_executor_stats': Bool(90300, None),
-    'log_file_mode': Integer(90300, None, 0, 511, None),
-    'log_filename': String(90300, None),
-    'logging_collector': Bool(90300, None),
-    'log_hostname': Bool(90300, None),
-    'logical_decoding_work_mem': Integer(130000, None, 64, 2147483647, 'kB'),
-    'log_line_prefix': String(90300, None),
-    'log_lock_waits': Bool(90300, None),
-    'log_min_duration_sample': Integer(130000, None, -1, 2147483647, 'ms'),
-    'log_min_duration_statement': Integer(90300, None, -1, 2147483647, 'ms'),
-    'log_min_error_statement': Enum(90300, None, ('debug5', 'debug4', 'debug3', 'debug2', 'debug1', 'info',
-                                                  'notice', 'warning', 'error', 'log', 'fatal', 'panic')),
-    'log_min_messages': Enum(90300, None, ('debug5', 'debug4', 'debug3', 'debug2', 'debug1', 'info',
-                                           'notice', 'warning', 'error', 'log', 'fatal', 'panic')),
-    'log_parameter_max_length': Integer(130000, None, -1, 1073741823, 'B'),
-    'log_parameter_max_length_on_error': Integer(130000, None, -1, 1073741823, 'B'),
-    'log_parser_stats': Bool(90300, None),
-    'log_planner_stats': Bool(90300, None),
-    'log_recovery_conflict_waits': Bool(140000, None),
-    'log_replication_commands': Bool(90500, None),
-    'log_rotation_age': Integer(90300, None, 0, 35791394, 'min'),
-    'log_rotation_size': Integer(90300, None, 0, 2097151, 'kB'),
-    'log_startup_progress_interval': Integer(150000, None, 0, 2147483647, 'ms'),
-    'log_statement': Enum(90300, None, ('none', 'ddl', 'mod', 'all')),
-    'log_statement_sample_rate': Real(130000, None, 0, 1, None),
-    'log_statement_stats': Bool(90300, None),
-    'log_temp_files': Integer(90300, None, -1, 2147483647, 'kB'),
-    'log_timezone': String(90300, None),
-    'log_transaction_sample_rate': Real(120000, None, 0, 1, None),
-    'log_truncate_on_rotation': Bool(90300, None),
-    'maintenance_io_concurrency': Integer(130000, None, 0, 1000, None),
-    'maintenance_work_mem': Integer(90300, None, 1024, 2147483647, 'kB'),
-    'max_connections': (
-        Integer(90300, 90600, 1, 8388607, None),
-        Integer(90600, None, 1, 262143, None)
-    ),
-    'max_files_per_process': (
-        Integer(90300, 130000, 25, 2147483647, None),
-        Integer(130000, None, 64, 2147483647, None)
-    ),
-    'max_locks_per_transaction': Integer(90300, None, 10, 2147483647, None),
-    'max_logical_replication_workers': Integer(100000, None, 0, 262143, None),
-    'max_parallel_maintenance_workers': Integer(110000, None, 0, 1024, None),
-    'max_parallel_workers': Integer(100000, None, 0, 1024, None),
-    'max_parallel_workers_per_gather': Integer(90600, None, 0, 1024, None),
-    'max_pred_locks_per_page': Integer(100000, None, 0, 2147483647, None),
-    'max_pred_locks_per_relation': Integer(100000, None, -2147483648, 2147483647, None),
-    'max_pred_locks_per_transaction': Integer(90300, None, 10, 2147483647, None),
-    'max_prepared_transactions': (
-        Integer(90300, 90600, 0, 8388607, None),
-        Integer(90600, None, 0, 262143, None)
-    ),
-    'max_replication_slots': (
-        Integer(90400, 90600, 0, 8388607, None),
-        Integer(90600, None, 0, 262143, None)
-    ),
-    'max_slot_wal_keep_size': Integer(130000, None, -1, 2147483647, 'MB'),
-    'max_stack_depth': Integer(90300, None, 100, 2147483647, 'kB'),
-    'max_standby_archive_delay': Integer(90300, None, -1, 2147483647, 'ms'),
-    'max_standby_streaming_delay': Integer(90300, None, -1, 2147483647, 'ms'),
-    'max_sync_workers_per_subscription': Integer(100000, None, 0, 262143, None),
-    'max_wal_senders': (
-        Integer(90300, 90600, 0, 8388607, None),
-        Integer(90600, None, 0, 262143, None)
-    ),
-    'max_wal_size': (
-        Integer(90500, 100000, 2, 2147483647, '16MB'),
-        Integer(100000, None, 2, 2147483647, 'MB')
-    ),
-    'max_worker_processes': (
-        Integer(90400, 90600, 1, 8388607, None),
-        Integer(90600, None, 0, 262143, None)
-    ),
-    'min_dynamic_shared_memory': Integer(140000, None, 0, 2147483647, 'MB'),
-    'min_parallel_index_scan_size': Integer(100000, None, 0, 715827882, '8kB'),
-    'min_parallel_relation_size': Integer(90600, 100000, 0, 715827882, '8kB'),
-    'min_parallel_table_scan_size': Integer(100000, None, 0, 715827882, '8kB'),
-    'min_wal_size': (
-        Integer(90500, 100000, 2, 2147483647, '16MB'),
-        Integer(100000, None, 2, 2147483647, 'MB')
-    ),
-    'old_snapshot_threshold': Integer(90600, None, -1, 86400, 'min'),
-    'operator_precedence_warning': Bool(90500, 140000),
-    'parallel_leader_participation': Bool(110000, None),
-    'parallel_setup_cost': Real(90600, None, 0, 1.79769e+308, None),
-    'parallel_tuple_cost': Real(90600, None, 0, 1.79769e+308, None),
-    'password_encryption': (
-        Bool(90300, 100000),
-        Enum(100000, None, ('md5', 'scram-sha-256'))
-    ),
-    'plan_cache_mode': Enum(120000, None, ('auto', 'force_generic_plan', 'force_custom_plan')),
-    'port': Integer(90300, None, 1, 65535, None),
-    'post_auth_delay': Integer(90300, None, 0, 2147, 's'),
-    'pre_auth_delay': Integer(90300, None, 0, 60, 's'),
-    'quote_all_identifiers': Bool(90300, None),
-    'random_page_cost': Real(90300, None, 0, 1.79769e+308, None),
-    'recovery_init_sync_method': Enum(140000, None, ('fsync', 'syncfs')),
-    'recovery_prefetch': EnumBool(150000, None, ('try',)),
-    'recursive_worktable_factor': Real(150000, None, 0.001, 1e+06, None),
-    'remove_temp_files_after_crash': Bool(140000, None),
-    'replacement_sort_tuples': Integer(90600, 110000, 0, 2147483647, None),
-    'restart_after_crash': Bool(90300, None),
-    'row_security': Bool(90500, None),
-    'search_path': String(90300, None),
-    'seq_page_cost': Real(90300, None, 0, 1.79769e+308, None),
-    'session_preload_libraries': String(90400, None),
-    'session_replication_role': Enum(90300, None, ('origin', 'replica', 'local')),
-    'shared_buffers': Integer(90300, None, 16, 1073741823, '8kB'),
-    'shared_memory_type': Enum(120000, None, ('sysv', 'mmap')),
-    'shared_preload_libraries': String(90300, None),
-    'sql_inheritance': Bool(90300, 100000),
-    'ssl': Bool(90300, None),
-    'ssl_ca_file': String(90300, None),
-    'ssl_cert_file': String(90300, None),
-    'ssl_ciphers': String(90300, None),
-    'ssl_crl_dir': String(140000, None),
-    'ssl_crl_file': String(90300, None),
-    'ssl_dh_params_file': String(100000, None),
-    'ssl_ecdh_curve': String(90400, None),
-    'ssl_key_file': String(90300, None),
-    'ssl_max_protocol_version': Enum(120000, None, ('', 'tlsv1', 'tlsv1.1', 'tlsv1.2', 'tlsv1.3')),
-    'ssl_min_protocol_version': Enum(120000, None, ('tlsv1', 'tlsv1.1', 'tlsv1.2', 'tlsv1.3')),
-    'ssl_passphrase_command': String(110000, None),
-    'ssl_passphrase_command_supports_reload': Bool(110000, None),
-    'ssl_prefer_server_ciphers': Bool(90400, None),
-    'ssl_renegotiation_limit': Integer(90300, 90500, 0, 2147483647, 'kB'),
-    'standard_conforming_strings': Bool(90300, None),
-    'statement_timeout': Integer(90300, None, 0, 2147483647, 'ms'),
-    'stats_fetch_consistency': Enum(150000, None, ('none', 'cache', 'snapshot')),
-    'stats_temp_directory': String(90300, 150000),
-    'superuser_reserved_connections': (
-        Integer(90300, 90600, 0, 8388607, None),
-        Integer(90600, None, 0, 262143, None)
-    ),
-    'synchronize_seqscans': Bool(90300, None),
-    'synchronous_commit': (
-        EnumBool(90300, 90600, ('local', 'remote_write')),
-        EnumBool(90600, None, ('local', 'remote_write', 'remote_apply'))
-    ),
-    'synchronous_standby_names': String(90300, None),
-    'syslog_facility': Enum(90300, None, ('local0', 'local1', 'local2', 'local3',
-                                          'local4', 'local5', 'local6', 'local7')),
-    'syslog_ident': String(90300, None),
-    'syslog_sequence_numbers': Bool(90600, None),
-    'syslog_split_messages': Bool(90600, None),
-    'tcp_keepalives_count': Integer(90300, None, 0, 2147483647, None),
-    'tcp_keepalives_idle': Integer(90300, None, 0, 2147483647, 's'),
-    'tcp_keepalives_interval': Integer(90300, None, 0, 2147483647, 's'),
-    'tcp_user_timeout': Integer(120000, None, 0, 2147483647, 'ms'),
-    'temp_buffers': Integer(90300, None, 100, 1073741823, '8kB'),
-    'temp_file_limit': Integer(90300, None, -1, 2147483647, 'kB'),
-    'temp_tablespaces': String(90300, None),
-    'TimeZone': String(90300, None),
-    'timezone_abbreviations': String(90300, None),
-    'trace_notify': Bool(90300, None),
-    'trace_recovery_messages': Enum(90300, None, ('debug5', 'debug4', 'debug3', 'debug2',
-                                                  'debug1', 'log', 'notice', 'warning', 'error')),
-    'trace_sort': Bool(90300, None),
-    'track_activities': Bool(90300, None),
-    'track_activity_query_size': (
-        Integer(90300, 110000, 100, 102400, None),
-        Integer(110000, 130000, 100, 102400, 'B'),
-        Integer(130000, None, 100, 1048576, 'B')
-    ),
-    'track_commit_timestamp': Bool(90500, None),
-    'track_counts': Bool(90300, None),
-    'track_functions': Enum(90300, None, ('none', 'pl', 'all')),
-    'track_io_timing': Bool(90300, None),
-    'track_wal_io_timing': Bool(140000, None),
-    'transaction_deferrable': Bool(90300, None),
-    'transaction_isolation': Enum(90300, None, ('serializable', 'repeatable read',
-                                                'read committed', 'read uncommitted')),
-    'transaction_read_only': Bool(90300, None),
-    'transform_null_equals': Bool(90300, None),
-    'unix_socket_directories': String(90300, None),
-    'unix_socket_group': String(90300, None),
-    'unix_socket_permissions': Integer(90300, None, 0, 511, None),
-    'update_process_title': Bool(90300, None),
-    'vacuum_cleanup_index_scale_factor': Real(110000, 140000, 0, 1e+10, None),
-    'vacuum_cost_delay': (
-        Integer(90300, 120000, 0, 100, 'ms'),
-        Real(120000, None, 0, 100, 'ms')
-    ),
-    'vacuum_cost_limit': Integer(90300, None, 1, 10000, None),
-    'vacuum_cost_page_dirty': Integer(90300, None, 0, 10000, None),
-    'vacuum_cost_page_hit': Integer(90300, None, 0, 10000, None),
-    'vacuum_cost_page_miss': Integer(90300, None, 0, 10000, None),
-    'vacuum_defer_cleanup_age': Integer(90300, None, 0, 1000000, None),
-    'vacuum_failsafe_age': Integer(140000, None, 0, 2100000000, None),
-    'vacuum_freeze_min_age': Integer(90300, None, 0, 1000000000, None),
-    'vacuum_freeze_table_age': Integer(90300, None, 0, 2000000000, None),
-    'vacuum_multixact_failsafe_age': Integer(140000, None, 0, 2100000000, None),
-    'vacuum_multixact_freeze_min_age': Integer(90300, None, 0, 1000000000, None),
-    'vacuum_multixact_freeze_table_age': Integer(90300, None, 0, 2000000000, None),
-    'wal_buffers': Integer(90300, None, -1, 262143, '8kB'),
-    'wal_compression': (
-        Bool(90500, 150000),
-        EnumBool(150000, None, ('pglz', 'lz4', 'zstd'))
-    ),
-    'wal_consistency_checking': String(100000, None),
-    'wal_decode_buffer_size': Integer(150000, None, 65536, 1073741823, 'B'),
-    'wal_init_zero': Bool(120000, None),
-    'wal_keep_segments': Integer(90300, 130000, 0, 2147483647, None),
-    'wal_keep_size': Integer(130000, None, 0, 2147483647, 'MB'),
-    'wal_level': (
-        Enum(90300, 90400, ('minimal', 'archive', 'hot_standby')),
-        Enum(90400, 90600, ('minimal', 'archive', 'hot_standby', 'logical')),
-        Enum(90600, None, ('minimal', 'replica', 'logical'))
-    ),
-    'wal_log_hints': Bool(90400, None),
-    'wal_receiver_create_temp_slot': Bool(130000, None),
-    'wal_receiver_status_interval': Integer(90300, None, 0, 2147483, 's'),
-    'wal_receiver_timeout': Integer(90300, None, 0, 2147483647, 'ms'),
-    'wal_recycle': Bool(120000, None),
-    'wal_retrieve_retry_interval': Integer(90500, None, 1, 2147483647, 'ms'),
-    'wal_sender_timeout': Integer(90300, None, 0, 2147483647, 'ms'),
-    'wal_skip_threshold': Integer(130000, None, 0, 2147483647, 'kB'),
-    'wal_sync_method': Enum(90300, None, ('fsync', 'fdatasync', 'open_sync', 'open_datasync')),
-    'wal_writer_delay': Integer(90300, None, 1, 10000, 'ms'),
-    'wal_writer_flush_after': Integer(90600, None, 0, 2147483647, '8kB'),
-    'work_mem': Integer(90300, None, 64, 2147483647, 'kB'),
-    'xmlbinary': Enum(90300, None, ('base64', 'hex')),
-    'xmloption': Enum(90300, None, ('content', 'document')),
-    'zero_damaged_pages': Bool(90300, None)
-})
+#  key  - parameter name
+#  value - variable length tuple of `_Transformable` objects. Each object in the tuple represents a different
+#          validation of the GUC across postgres versions. If a GUC validation has never changed over time, then it will
+#          have a single object in the tuple. For example, `password_encryption` used to be a boolean GUC up to Postgres
+#          10, at which point it started being an enum. In that case the value of `password_encryption` would be a tuple
+#          of 2 `_Transformable` objects (`Bool` and `Enum`, respectively), each one reprensenting a different
+#          validation rule.
+parameters = CaseInsensitiveDict()
+recovery_parameters = CaseInsensitiveDict()
 
 
-recovery_parameters = CaseInsensitiveDict({
-    'archive_cleanup_command': String(90300, None),
-    'pause_at_recovery_target': Bool(90300, 90500),
-    'primary_conninfo': String(90300, None),
-    'primary_slot_name': String(90400, None),
-    'promote_trigger_file': String(120000, None),
-    'recovery_end_command': String(90300, None),
-    'recovery_min_apply_delay': Integer(90400, None, 0, 2147483647, 'ms'),
-    'recovery_target': Enum(90400, None, ('immediate', '')),
-    'recovery_target_action': Enum(90500, None, ('pause', 'promote', 'shutdown')),
-    'recovery_target_inclusive': Bool(90300, None),
-    'recovery_target_lsn': String(100000, None),
-    'recovery_target_name': String(90400, None),
-    'recovery_target_time': String(90300, None),
-    'recovery_target_timeline': String(90300, None),
-    'recovery_target_xid': String(90300, None),
-    'restore_command': String(90300, None),
-    'standby_mode': Bool(90300, 120000),
-    'trigger_file': String(90300, 120000)
-})
+class ValidatorFactoryNoType(PatroniException):
+    """Raised when a validator spec misses a type."""
 
 
-def _transform_parameter_value(validators, version, name, value):
-    validators = validators.get(name)
-    if validators:
-        for validator in (validators if isinstance(validators[0], tuple) else [validators]):
+class ValidatorFactoryInvalidType(PatroniException):
+    """Raised when a validator spec contains an invalid type."""
+
+
+class ValidatorFactoryInvalidSpec(PatroniException):
+    """Raised when a validator spec contains an invalid set of attributes."""
+
+
+class ValidatorFactory:
+    """Factory class used to build Patroni validator objects based on the given specs."""
+
+    TYPES: Dict[str, Type[_Transformable]] = {cls.__name__: cls for cls in _Transformable.get_subclasses()}
+
+    def __new__(cls, validator: Dict[str, Any]) -> _Transformable:
+        """Parse a given Postgres GUC *validator* into the corresponding Patroni validator object.
+
+        :param validator: a validator spec for a given parameter. It usually comes from a parsed YAML file.
+
+        :returns: the Patroni validator object that corresponds to the specification found in *validator*.
+
+        :raises:
+            :class:`ValidatorFactoryNoType`: if *validator* contains no ``type`` key.
+            :class:`ValidatorFactoryInvalidType`: if ``type`` key from *validator* contains an invalid value.
+            :class:`ValidatorFactoryInvalidSpec`: if *validator* contains an invalid set of attributes for the given
+                ``type``.
+
+        :Example:
+
+            If a given validator was defined as follows in the YAML file:
+
+            ```yaml
+            - type: String
+            version_from: 90300
+            version_till: null
+            ```
+
+            Then this method would receive *validator* as:
+
+            ```python
+            {
+                'type': 'String',
+                'version_from': 90300,
+                'version_till': None
+            }
+            ```
+
+            And this method would return a :class:`String`:
+
+            ```python
+            String(90300, None)
+            ```
+        """
+        validator = deepcopy(validator)
+        try:
+            type_ = validator.pop('type')
+        except KeyError as exc:
+            raise ValidatorFactoryNoType('Validator contains no type.') from exc
+
+        if type_ not in cls.TYPES:
+            raise ValidatorFactoryInvalidType(f'Unexpected validator type: `{type_}`.')
+
+        for key, value in validator.items():
+            # :func:`_transform_parameter_value` expects :class:`tuple` instead of :class:`list`
+            if isinstance(value, list):
+                tmp_value: List[Any] = value
+                validator[key] = tuple(tmp_value)
+
+        try:
+            return cls.TYPES[type_](**validator)
+        except Exception as exc:
+            raise ValidatorFactoryInvalidSpec(
+                f'Failed to parse `{type_}` validator (`{validator}`): `{str(exc)}`.') from exc
+
+
+def _get_postgres_guc_validators(config: Dict[str, Any], parameter: str) -> Tuple[_Transformable, ...]:
+    """Get all validators of *parameter* from *config*.
+
+    Loop over all validators specs of *parameter* and return them parsed as Patroni validators.
+
+    :param config: Python object corresponding to an YAML file, with values of either ``parameters`` or
+        ``recovery_parameters`` key.
+    :param parameter: name of the parameter found under *config* which validators should be parsed and returned.
+
+    :rtype: yields any exception that is faced while parsing a validator spec into a Patroni validator object.
+    """
+    validators: List[_Transformable] = []
+    for validator_spec in config.get(parameter, []):
+        try:
+            validator = ValidatorFactory(validator_spec)
+            validators.append(validator)
+        except (ValidatorFactoryNoType, ValidatorFactoryInvalidType, ValidatorFactoryInvalidSpec) as exc:
+            logger.warning('Faced an issue while parsing a validator for parameter `%s`: `%r`', parameter, exc)
+
+    return tuple(validators)
+
+
+class InvalidGucValidatorsFile(PatroniException):
+    """Raised when reading or parsing of a YAML file faces an issue."""
+
+
+def _read_postgres_gucs_validators_file(file: str) -> Dict[str, Any]:
+    """Read an YAML file and return the corresponding Python object.
+
+    :param file: path to the file to be read. It is expected to be encoded with ``UTF-8``, and to be a YAML document.
+
+    :returns: the YAML content parsed into a Python object. If any issue is faced while reading/parsing the file, then
+        return ``None``.
+
+    :raises:
+        :class:`InvalidGucValidatorsFile`: if faces an issue while reading or parsing *file*.
+    """
+    try:
+        with open(file, encoding='UTF-8') as stream:
+            return yaml.safe_load(stream)
+    except Exception as exc:
+        raise InvalidGucValidatorsFile(
+            f'Unexpected issue while reading parameters file `{file}`: `{str(exc)}`.') from exc
+
+
+def _load_postgres_gucs_validators() -> None:
+    """Load all Postgres GUC validators from YAML files.
+
+    Recursively walk through ``available_parameters`` directory and load validators of each found YAML file into
+    ``parameters`` and/or ``recovery_parameters`` variables.
+
+    Walk through directories in top-down fashion and for each of them:
+        * Sort files by name;
+        * Load validators from YAML files that were found.
+
+    Any problem faced while reading or parsing files will be logged as a ``WARNING`` by the child function, and the
+    corresponding file or validator will be ignored.
+
+    By default Patroni only ships the file ``0_postgres.yml``, which contains Community Postgres GUCs validators, but
+    that behavior can be extended. For example: if a vendor wants to add GUC validators to Patroni for covering a custom
+    Postgres build, then they can create their custom YAML files under ``available_parameters`` directory.
+
+    Each YAML file may contain either or both of these root attributes, here called sections:
+        * ``parameters``: general GUCs that would be written to ``postgresql.conf``;
+        * ``recovery_parameters``: recovery related GUCs that would be written to ``recovery.conf`` (Patroni later
+            writes them to ``postgresql.conf`` if running PG 12 and above).
+
+    Then, each of these sections, if specified, may contain one or more attributes with the following structure:
+        * key: the name of a GUC;
+        * value: a list of validators. Each item in the list must contain a ``type`` attribute, which must be one among:
+            * ``Bool``; or
+            * ``Integer``; or
+            * ``Real``; or
+            * ``Enum``; or
+            * ``EnumBool``; or
+            * ``String``.
+
+            Besides the ``type`` attribute, it should also contain all the required attributes as per the corresponding
+            class in this module.
+
+    .. seealso::
+        * :class:`Bool`;
+        * :class:`Integer`;
+        * :class:`Real`;
+        * :class:`Enum`;
+        * :class:`EnumBool`;
+        * :class:`String`.
+
+    :Example:
+
+        This is a sample content for an YAML file based on Postgres GUCs, showing each of the supported types and
+        sections:
+
+        ```yaml
+        parameters:
+          archive_command:
+          - type: String
+            version_from: 90300
+            version_till: null
+          archive_mode:
+          - type: Bool
+            version_from: 90300
+            version_till: 90500
+          - type: EnumBool
+            version_from: 90500
+            version_till: null
+            possible_values:
+            - always
+          archive_timeout:
+          - type: Integer
+            version_from: 90300
+            version_till: null
+            min_val: 0
+            max_val: 1073741823
+            unit: s
+          autovacuum_vacuum_cost_delay:
+          - type: Integer
+            version_from: 90300
+            version_till: 120000
+            min_val: -1
+            max_val: 100
+            unit: ms
+          - type: Real
+            version_from: 120000
+            version_till: null
+            min_val: -1
+            max_val: 100
+            unit: ms
+          client_min_messages:
+          - type: Enum
+            version_from: 90300
+            version_till: null
+            possible_values:
+            - debug5
+            - debug4
+            - debug3
+            - debug2
+            - debug1
+            - log
+            - notice
+            - warning
+            - error
+        recovery_parameters:
+          archive_cleanup_command:
+          - type: String
+            version_from: 90300
+            version_till: null
+        ```
+    """
+    conf_dir = os.path.join(
+        os.path.dirname(os.path.abspath(__file__)),
+        'available_parameters',
+    )
+    yaml_files: List[str] = []
+
+    for root, _, files in os.walk(conf_dir):
+        for file in sorted(files):
+            full_path = os.path.join(root, file)
+            if file.lower().endswith(('.yml', '.yaml')):
+                yaml_files.append(full_path)
+            else:
+                logger.info('Ignored a non-YAML file found under `available_parameters` directory: `%s`.', full_path)
+
+    for file in yaml_files:
+        try:
+            config: Dict[str, Any] = _read_postgres_gucs_validators_file(file)
+        except InvalidGucValidatorsFile as exc:
+            logger.warning(str(exc))
+            continue
+
+        logger.debug(f'Parsing validators from file `{file}`.')
+
+        mapping = {
+            'parameters': parameters,
+            'recovery_parameters': recovery_parameters,
+        }
+
+        for section in ['parameters', 'recovery_parameters']:
+            section_var = mapping[section]
+
+            config_section = config.get(section, {})
+            for parameter in config_section.keys():
+                section_var[parameter] = _get_postgres_guc_validators(config_section, parameter)
+
+
+_load_postgres_gucs_validators()
+
+
+def _transform_parameter_value(validators: MutableMapping[str, Tuple[_Transformable, ...]],
+                               version: int, name: str, value: Any,
+                               available_gucs: CaseInsensitiveSet) -> Optional[Any]:
+    """Validate *value* of GUC *name* for Postgres *version* using defined *validators* and *available_gucs*.
+
+    :param validators: a dictionary of all GUCs across all Postgres versions. Each key is the name of a Postgres GUC,
+        and the corresponding value is a variable length tuple of :class:`_Transformable`. Each item is a validation
+        rule for the GUC for a given range of Postgres versions. Should either contain recovery GUCs or general GUCs,
+        not both.
+    :param version: Postgres version to validate the GUC against.
+    :param name: name of the Postgres GUC.
+    :param value: value of the Postgres GUC.
+    :param available_gucs: a set of all GUCs available in Postgres *version*. Each item is the name of a Postgres
+        GUC. Used for a couple purposes:
+        * Disallow writing GUCs to ``postgresql.conf`` (or ``recovery.conf``) that does not exist in Postgres *version*;
+        * Avoid ignoring GUC *name* if it does not have a validator in *validators*, but is a valid GUC in Postgres
+            *version*.
+
+    :returns: the return value may be one among:
+        * *value* transformed to the expected format for GUC *name* in Postgres *version*, if *name* is present in
+            *available_gucs* and has a validator in *validators* for the corresponding Postgres *version*; or
+        * The own *value* if *name* is present in *available_gucs* but not in *validators*; or
+        * ``None`` if *name* is not present in *available_gucs*.
+    """
+    if name in available_gucs:
+        for validator in validators.get(name, ()) or ():
             if version >= validator.version_from and\
                     (validator.version_till is None or version < validator.version_till):
                 return validator.transform(name, value)
+        # Ideally we should have a validator in *validators*. However, if none is available, we will not discard a
+        # setting that exists in Postgres *version*, but rather allow the value with no validation.
+        return value
     logger.warning('Removing unexpected parameter=%s value=%s from the config', name, value)
 
 
-def transform_postgresql_parameter_value(version, name, value):
-    if '.' in name:
+def transform_postgresql_parameter_value(version: int, name: str, value: Any,
+                                         available_gucs: CaseInsensitiveSet) -> Optional[Any]:
+    """Validate *value* of GUC *name* for Postgres *version* using ``parameters`` and *available_gucs*.
+
+    :param version: Postgres version to validate the GUC against.
+    :param name: name of the Postgres GUC.
+    :param value: value of the Postgres GUC.
+    :param available_gucs: a set of all GUCs available in Postgres *version*. Each item is the name of a Postgres
+        GUC. Used for a couple purposes:
+
+            * Disallow writing GUCs to ``postgresql.conf`` that does not exist in Postgres *version*;
+            * Avoid ignoring GUC *name* if it does not have a validator in ``parameters``, but is a valid GUC in
+                Postgres *version*.
+
+    :returns: The return value may be one among:
+
+        * The original *value* if *name* seems to be an extension GUC (contains a period '.'); or
+        * ``None`` if **name** is a recovery GUC; or
+        * *value* transformed to the expected format for GUC *name* in Postgres *version* using validators defined in
+            ``parameters``. Can also return ``None``. See :func:`_transform_parameter_value`.
+    """
+    if '.' in name and name not in parameters:
+        # likely an extension GUC, so just return as it is. Otherwise, if `name` is in `parameters`, it's likely a
+        # namespaced GUC from a custom Postgres build, so we treat that over the usual validation means.
         return value
     if name in recovery_parameters:
         return None
-    return _transform_parameter_value(parameters, version, name, value)
+    return _transform_parameter_value(parameters, version, name, value, available_gucs)
 
 
-def transform_recovery_parameter_value(version, name, value):
-    return _transform_parameter_value(recovery_parameters, version, name, value)
+def transform_recovery_parameter_value(version: int, name: str, value: Any,
+                                       available_gucs: CaseInsensitiveSet) -> Optional[Any]:
+    """Validate *value* of GUC *name* for Postgres *version* using ``recovery_parameters`` and *available_gucs*.
+
+    :param version: Postgres version to validate the recovery GUC against.
+    :param name: name of the Postgres recovery GUC.
+    :param value: value of the Postgres recovery GUC.
+    :param available_gucs: a set of all GUCs available in Postgres *version*. Each item is the name of a Postgres
+        GUC. Used for a couple purposes:
+
+            * Disallow writing GUCs to ``recovery.conf`` (or ``postgresql.conf`` depending on *version*), that does not
+                exist in Postgres *version*;
+            * Avoid ignoring recovery GUC *name* if it does not have a validator in ``recovery_parameters``, but is a
+                valid GUC in Postgres *version*.
+
+    :returns: *value* transformed to the expected format for recovery GUC *name* in Postgres *version* using validators
+        defined in ``recovery_parameters``. It can also return ``None``. See :func:`_transform_parameter_value`.
+    """
+    # Recovery settings are not present in ``postgres --describe-config`` output of Postgres <= 11. In that case we
+    # just pass down the list of settings defined in Patroni validators so :func:`_transform_parameter_value` will not
+    # discard the recovery GUCs when running Postgres <= 11.
+    # NOTE: At the moment this change was done Postgres 11 was almost EOL, and had been likely extensively used with
+    # Patroni, so we should be able to rely solely on Patroni validators as the source of truth.
+    return _transform_parameter_value(
+        recovery_parameters, version, name, value,
+        available_gucs if version >= 120000 else CaseInsensitiveSet(recovery_parameters.keys()))

patroni/psycopg.py

@@ -1,3 +1,14 @@
+"""Abstraction layer for :mod:`psycopg` module.
+
+This module is able to handle both :mod:`pyscopg2` and :mod:`psycopg`, and it exposes a common interface for both.
+:mod:`psycopg2` takes precedence. :mod:`psycopg` will only be used if :mod:`psycopg2` is either absent or older than
+``2.5.4``.
+"""
+from typing import Any, Optional, TYPE_CHECKING, Union
+if TYPE_CHECKING:  # pragma: no cover
+    from psycopg import Connection
+    from psycopg2 import connection, cursor
+
 __all__ = ['connect', 'quote_ident', 'quote_literal', 'DatabaseError', 'Error', 'OperationalError', 'ProgrammingError']
 
 _legacy = False
@@ -14,7 +25,18 @@ try:
     except ImportError:
         _legacy = True
 
-    def quote_literal(value, conn=None):
+    def quote_literal(value: Any, conn: Optional[Any] = None) -> str:
+        """Quote *value* as a SQL literal.
+
+        .. note::
+            *value* is quoted through :mod:`psycopg2` adapters.
+
+        :param value: value to be quoted.
+        :param conn: if a connection is given then :func:`quote_literal` checks if any special handling based on server
+            parameters needs to be applied to *value* before quoting it as a SQL literal.
+
+        :returns: *value* quoted as a SQL literal.
+        """
         value = adapt(value)
         if conn:
             value.prepare(conn)
@@ -22,19 +44,58 @@ try:
 except ImportError:
     from psycopg import connect as __connect, sql, Error, DatabaseError, OperationalError, ProgrammingError
 
-    def _connect(*args, **kwargs):
-        ret = __connect(*args, **kwargs)
-        ret.server_version = ret.pgconn.server_version  # compatibility with psycopg2
+    def _connect(dsn: Optional[str] = None, **kwargs: Any) -> 'Connection[Any]':
+        """Call :func:`psycopg.connect` with *dsn* and ``**kwargs``.
+
+        .. note::
+            Will create ``server_version`` attribute in the returning connection, so it keeps compatibility with the
+            object that would be returned by :func:`psycopg2.connect`.
+
+        :param dsn: DSN to call :func:`psycopg.connect` with.
+        :param kwargs: keyword arguments to call :func:`psycopg.connect` with.
+
+        :returns: a connection to the database.
+        """
+        ret = __connect(dsn or "", **kwargs)
+        setattr(ret, 'server_version', ret.pgconn.server_version)  # compatibility with psycopg2
         return ret
 
-    def _quote_ident(value, conn):
-        return sql.Identifier(value).as_string(conn)
+    def _quote_ident(value: Any, scope: Any) -> str:
+        """Quote *value* as a SQL identifier.
 
-    def quote_literal(value, conn=None):
+        :param value: value to be quoted.
+        :param scope: connection to evaluate the returning string into.
+
+        :returns: *value* quoted as a SQL identifier.
+        """
+        return sql.Identifier(value).as_string(scope)
+
+    def quote_literal(value: Any, conn: Optional[Any] = None) -> str:
+        """Quote *value* as a SQL literal.
+
+        :param value: value to be quoted.
+        :param conn: connection to evaluate the returning string into.
+
+        :returns: *value* quoted as a SQL literal.
+        """
         return sql.Literal(value).as_string(conn)
 
 
-def connect(*args, **kwargs):
+def connect(*args: Any, **kwargs: Any) -> Union['connection', 'Connection[Any]']:
+    """Get a connection to the database.
+
+    .. note::
+        The connection will have ``autocommit`` enabled.
+
+        It also enforces ``search_path=pg_catalog`` for non-replication connections to mitigate security issues as
+        Patroni relies on superuser connections.
+
+    :param args: positional arguments to call :func:`~psycopg.connect` function from :mod:`psycopg` module.
+    :param kwargs: keyword arguments to call :func:`~psycopg.connect` function from :mod:`psycopg` module.
+
+    :returns: a connection to the database. Can be either a :class:`psycopg.Connection` if using :mod:`psycopg`, or a
+        :class:`psycopg2.extensions.connection` if using :mod:`psycopg2`.
+    """
     if kwargs and 'replication' not in kwargs and kwargs.get('fallback_application_name') != 'Patroni ctl':
         options = [kwargs['options']] if 'options' in kwargs else []
         options.append('-c search_path=pg_catalog')
@@ -44,7 +105,15 @@ def connect(*args, **kwargs):
     return ret
 
 
-def quote_ident(value, conn=None):
+def quote_ident(value: Any, conn: Optional[Union['cursor', 'connection', 'Connection[Any]']] = None) -> str:
+    """Quote *value* as a SQL identifier.
+
+    :param value: value to be quoted.
+    :param conn: connection to evaluate the returning string into. Can be either a :class:`psycopg.Connection` if
+        using :mod:`psycopg`, or a :class:`psycopg2.extensions.connection` if using :mod:`psycopg2`.
+
+    :returns: *value* quoted as a SQL identifier.
+    """
     if _legacy or conn is None:
         return '"{0}"'.format(value.replace('"', '""'))
     return _quote_ident(value, conn)

patroni/raft_controller.py

@@ -1,6 +1,7 @@
 import logging
 
-from .daemon import AbstractPatroniDaemon, abstract_main
+from .config import Config
+from .daemon import AbstractPatroniDaemon, abstract_main, get_base_arg_parser
 from .dcs.raft import KVStoreTTL
 
 logger = logging.getLogger(__name__)
@@ -8,22 +9,25 @@ logger = logging.getLogger(__name__)
 
 class RaftController(AbstractPatroniDaemon):
 
-    def __init__(self, config):
+    def __init__(self, config: Config) -> None:
         super(RaftController, self).__init__(config)
 
-        config = self.config.get('raft')
-        assert 'self_addr' in config
-        self._raft = KVStoreTTL(None, None, None, **config)
+        kvstore_config = self.config.get('raft')
+        assert 'self_addr' in kvstore_config
+        self._raft = KVStoreTTL(None, None, None, **kvstore_config)
 
-    def _run_cycle(self):
+    def _run_cycle(self) -> None:
         try:
             self._raft.doTick(self._raft.conf.autoTickPeriod)
         except Exception:
             logger.exception('doTick')
 
-    def _shutdown(self):
+    def _shutdown(self) -> None:
         self._raft.destroy()
 
 
-def main():
-    abstract_main(RaftController)
+def main() -> None:
+    parser = get_base_arg_parser()
+    args = parser.parse_args()
+
+    abstract_main(RaftController, args.configfile)

patroni/request.py

@@ -1,67 +1,186 @@
+"""Facilities for handling communication with Patroni's REST API."""
 import json
 import urllib3
 
+from typing import Any, Dict, Optional, Union
+
 from urllib.parse import urlparse, urlunparse
 
+from .config import Config
+from .dcs import Member
 from .utils import USER_AGENT
 
 
-class PatroniRequest(object):
+class HTTPSConnectionPool(urllib3.HTTPSConnectionPool):
 
-    def __init__(self, config, insecure=None):
+    def _validate_conn(self, *args: Any, **kwargs: Any) -> None:
+        """Override parent method to silence warnings about requests without certificate verification enabled."""
+
+
+class PatroniPoolManager(urllib3.PoolManager):
+
+    def __init__(self, *args: Any, **kwargs: Any) -> None:
+        super(PatroniPoolManager, self).__init__(*args, **kwargs)
+        self.pool_classes_by_scheme = {'http': urllib3.HTTPConnectionPool, 'https': HTTPSConnectionPool}
+
+
+class PatroniRequest(object):
+    """Wrapper for performing requests to Patroni's REST API.
+
+    Prepares the request manager with the configured settings before performing the request.
+    """
+
+    def __init__(self, config: Union[Config, Dict[str, Any]], insecure: Optional[bool] = None) -> None:
+        """Create a new :class:`PatroniRequest` instance with given *config*.
+
+        :param config: Patroni YAML configuration.
+        :param insecure: how to deal with SSL certs verification:
+
+            * If ``True`` it will perform REST API requests without verifying SSL certs; or
+            * If ``False`` it will perform REST API requests and verify SSL certs; or
+            * If ``None`` it will behave according to the value of ``ctl.insecure`` configuration; or
+            * If none of the above applies, then it falls back to ``False``.
+        """
         self._insecure = insecure
-        self._pool = urllib3.PoolManager(num_pools=10, maxsize=10)
+        self._pool = PatroniPoolManager(num_pools=10, maxsize=10)
         self.reload_config(config)
 
     @staticmethod
-    def _get_cfg_value(config, name):
-        return config.get('ctl', {}).get(name) or config.get('restapi', {}).get(name)
+    def _get_ctl_value(config: Union[Config, Dict[str, Any]], name: str, default: Any = None) -> Optional[Any]:
+        """Get value of *name* setting from the ``ctl`` section of the *config*.
 
-    def _apply_pool_param(self, param, value):
+        :param config: Patroni YAML configuration.
+        :param name: name of the setting value to be retrieved.
+
+        :returns: value of ``ctl.*name*`` if present, ``None`` otherwise.
+        """
+        return config.get('ctl', {}).get(name, default)
+
+    @staticmethod
+    def _get_restapi_value(config: Union[Config, Dict[str, Any]], name: str) -> Optional[Any]:
+        """Get value of *name* setting from the ``restapi`` section of the *config*.
+
+        :param config: Patroni YAML configuration.
+        :param name: name of the setting value to be retrieved.
+
+        :returns: value of ``restapi -> *name*`` if present, ``None`` otherwise.
+        """
+        return config.get('restapi', {}).get(name)
+
+    def _apply_pool_param(self, param: str, value: Any) -> None:
+        """Configure *param* as *value* in the request manager.
+
+        :param param: name of the setting to be changed.
+        :param value: new value for *param*. If ``None``, ``0``, ``False``, and similar values, then explicit *param*
+            declaration is removed, in which case it takes its default value, if any.
+        """
         if value:
             self._pool.connection_pool_kw[param] = value
         else:
             self._pool.connection_pool_kw.pop(param, None)
 
-    def _apply_ssl_file_param(self, config, name):
-        value = self._get_cfg_value(config, name + 'file')
+    def _apply_ssl_file_param(self, config: Union[Config, Dict[str, Any]], name: str) -> Union[str, None]:
+        """Apply a given SSL related param to the request manager.
+
+        :param config: Patroni YAML configuration.
+        :param name: prefix of the Patroni SSL related setting name. Currently, supports these:
+
+            * ``cert``: gets translated to ``certfile``
+            * ``key``: gets translated to ``keyfile``
+
+            Will attempt to fetch the requested key first from ``ctl`` section.
+
+        :returns: value of ``ctl.*name*file`` if present, ``None`` otherwise.
+        """
+        value = self._get_ctl_value(config, name + 'file')
         self._apply_pool_param(name + '_file', value)
         return value
 
-    def reload_config(self, config):
-        self._pool.headers = urllib3.make_headers(basic_auth=self._get_cfg_value(config, 'auth'), user_agent=USER_AGENT)
+    def reload_config(self, config: Union[Config, Dict[str, Any]]) -> None:
+        """Apply *config* to request manager.
+
+        Configure these HTTP headers for requests:
+
+            * ``authorization``: based on Patroni' CTL or REST API authentication config;
+            * ``user-agent``: based on ``patroni.utils.USER_AGENT``.
+
+        Also configure SSL related settings for requests:
+
+            * ``ca_certs`` is configured if ``ctl.cacert`` or ``restapi.cafile`` is available;
+            * ``cert``, ``key`` and ``key_password`` are configured if ``ctl.certfile`` is available.
+
+        :param config: Patroni YAML configuration.
+        """
+        # ``ctl -> auth`` is equivalent to ``ctl -> authentication -> username`` + ``:`` +
+        # ``ctl -> authentication -> password``. And the same for ``restapi -> auth``
+        basic_auth = self._get_ctl_value(config, 'auth') or self._get_restapi_value(config, 'auth')
+        self._pool.headers = urllib3.make_headers(basic_auth=basic_auth, user_agent=USER_AGENT)
+        self._pool.connection_pool_kw['cert_reqs'] = 'CERT_REQUIRED'
+
+        insecure = self._insecure if isinstance(self._insecure, bool)\
+            else self._get_ctl_value(config, 'insecure', False)
 
-        insecure = self._insecure if isinstance(self._insecure, bool) else config.get('ctl', {}).get('insecure', False)
         if self._apply_ssl_file_param(config, 'cert'):
-            #  With client certificate the cert_reqs must be set to CERT_REQUIRED even if insecure option is used
-            self._pool.connection_pool_kw['cert_reqs'] = 'CERT_REQUIRED'
-            #  The assert_hostname = False helps to silence warnings
-            self._pool.connection_pool_kw['assert_hostname'] = False if insecure else None
+            if insecure:  # The assert_hostname = False helps to silence warnings
+                self._pool.connection_pool_kw['assert_hostname'] = False
 
             self._apply_ssl_file_param(config, 'key')
-
-            password = self._get_cfg_value(config, 'keyfile_password')
+            password = self._get_ctl_value(config, 'keyfile_password')
             self._apply_pool_param('key_password', password)
         else:
-            self._pool.connection_pool_kw['cert_reqs'] = 'CERT_NONE' if insecure else 'CERT_REQUIRED'
+            if insecure:  # Disable server certificate validation if requested
+                self._pool.connection_pool_kw['cert_reqs'] = 'CERT_NONE'
+            self._pool.connection_pool_kw.pop('assert_hostname', None)
             self._pool.connection_pool_kw.pop('key_file', None)
 
-        cacert = config.get('ctl', {}).get('cacert') or config.get('restapi', {}).get('cafile')
+        cacert = self._get_ctl_value(config, 'cacert') or self._get_restapi_value(config, 'cafile')
         self._apply_pool_param('ca_certs', cacert)
 
-    def request(self, method, url, body=None, **kwargs):
+    def request(self, method: str, url: str, body: Optional[Any] = None,
+                **kwargs: Any) -> urllib3.response.HTTPResponse:
+        """Perform an HTTP request.
+
+        :param method: the HTTP method to be used, e.g. ``GET``.
+        :param url: the URL to be requested.
+        :param body: anything to be used as the request body.
+        :param kwargs: keyword arguments to be passed to :func:`urllib3.PoolManager.request`.
+
+        :returns: the response returned upon request.
+        """
         if body is not None and not isinstance(body, str):
             body = json.dumps(body)
         return self._pool.request(method.upper(), url, body=body, **kwargs)
 
-    def __call__(self, member, method='GET', endpoint=None, data=None, **kwargs):
-        url = member.api_url
+    def __call__(self, member: Member, method: str = 'GET', endpoint: Optional[str] = None,
+                 data: Optional[Any] = None, **kwargs: Any) -> urllib3.response.HTTPResponse:
+        """Turn :class:`PatroniRequest` into a callable object.
+
+        When called, perform a request through the manager.
+
+        :param member: DCS member so we can fetch from it the configured base URL for the REST API.
+        :param method: HTTP method to be used, e.g. ``GET``.
+        :param endpoint: URL path of this request, e.g. ``switchover``.
+        :param data: anything to be used as the request body.
+
+        :returns: the response returned upon request.
+        """
+        url = member.api_url or ''
         if endpoint:
             scheme, netloc, _, _, _, _ = urlparse(url)
             url = urlunparse((scheme, netloc, endpoint, '', '', ''))
         return self.request(method, url, data, **kwargs)
 
 
-def get(url, verify=True, **kwargs):
+def get(url: str, verify: bool = True, **kwargs: Any) -> urllib3.response.HTTPResponse:
+    """Perform an HTTP GET request.
+
+    .. note::
+        It uses :class:`PatroniRequest` so all relevant configuration is applied before processing the request.
+
+    :param url: full URL for this GET request.
+    :param verify: if it should verify SSL certificates when processing the request.
+
+    :returns: the response returned from the request.
+    """
     http = PatroniRequest({}, not verify)
     return http.request('GET', url, **kwargs)

patroni/scripts/aws.py

@@ -5,20 +5,22 @@ import logging
 import sys
 import boto3
 
-from ..utils import Retry, RetryFailedError
-
 from botocore.exceptions import ClientError
 from botocore.utils import IMDSFetcher
 
+from typing import Any, Optional
+
+from ..utils import Retry, RetryFailedError
+
 logger = logging.getLogger(__name__)
 
 
 class AWSConnection(object):
 
-    def __init__(self, cluster_name):
+    def __init__(self, cluster_name: Optional[str]) -> None:
         self.available = False
         self.cluster_name = cluster_name if cluster_name is not None else 'unknown'
-        self._retry = Retry(deadline=300, max_delay=30, max_tries=-1, retry_exceptions=(ClientError,))
+        self._retry = Retry(deadline=300, max_delay=30, max_tries=-1, retry_exceptions=ClientError)
         try:
             # get the instance id
             fetcher = IMDSFetcher(timeout=2.1)
@@ -38,13 +40,13 @@ class AWSConnection(object):
                 return
             self.available = True
 
-    def retry(self, *args, **kwargs):
+    def retry(self, *args: Any, **kwargs: Any) -> Any:
         return self._retry.copy()(*args, **kwargs)
 
-    def aws_available(self):
+    def aws_available(self) -> bool:
         return self.available
 
-    def _tag_ebs(self, conn, role):
+    def _tag_ebs(self, conn: Any, role: str) -> None:
         """ set tags, carrying the cluster name, instance role and instance id for the EBS storage """
         tags = [{'Key': 'Name', 'Value': 'spilo_' + self.cluster_name},
                 {'Key': 'Role', 'Value': role},
@@ -52,16 +54,16 @@ class AWSConnection(object):
         volumes = conn.volumes.filter(Filters=[{'Name': 'attachment.instance-id', 'Values': [self.instance_id]}])
         conn.create_tags(Resources=[v.id for v in volumes], Tags=tags)
 
-    def _tag_ec2(self, conn, role):
+    def _tag_ec2(self, conn: Any, role: str) -> None:
         """ tag the current EC2 instance with a cluster role """
         tags = [{'Key': 'Role', 'Value': role}]
         conn.create_tags(Resources=[self.instance_id], Tags=tags)
 
-    def on_role_change(self, new_role):
+    def on_role_change(self, new_role: str) -> bool:
         if not self.available:
             return False
         try:
-            conn = boto3.resource('ec2', region_name=self.region)
+            conn = boto3.resource('ec2', region_name=self.region)  # type: ignore
             self.retry(self._tag_ec2, conn, new_role)
             self.retry(self._tag_ebs, conn, new_role)
         except RetryFailedError:

patroni/scripts/wale_restore.py

@@ -31,7 +31,8 @@ import subprocess
 import sys
 import time
 
-from collections import namedtuple
+from enum import IntEnum
+from typing import Any, List, NamedTuple, Optional, Tuple, TYPE_CHECKING
 
 from .. import psycopg
 
@@ -42,15 +43,14 @@ si_prefixes = ['K', 'M', 'G', 'T', 'P', 'E', 'Z', 'Y']
 
 
 # Meaningful names to the exit codes used by WALERestore
-ExitCode = type('Enum', (), {
-    'SUCCESS': 0,  #: Succeeded
-    'RETRY_LATER': 1,  #: External issue, retry later
-    'FAIL': 2  #: Don't try again unless configuration changes
-})
+class ExitCode(IntEnum):
+    SUCCESS = 0  #: Succeeded
+    RETRY_LATER = 1  #: External issue, retry later
+    FAIL = 2  #: Don't try again unless configuration changes
 
 
 # We need to know the current PG version in order to figure out the correct WAL directory name
-def get_major_version(data_dir):
+def get_major_version(data_dir: str) -> float:
     version_file = os.path.join(data_dir, 'PG_VERSION')
     if os.path.isfile(version_file):  # version file exists
         try:
@@ -61,7 +61,7 @@ def get_major_version(data_dir):
     return 0.0
 
 
-def repr_size(n_bytes):
+def repr_size(n_bytes: float) -> str:
     """
     >>> repr_size(1000)
     '1000 Bytes'
@@ -77,7 +77,7 @@ def repr_size(n_bytes):
     return '{0} {1}iB'.format(round(n_bytes, 1), si_prefixes[i])
 
 
-def size_as_bytes(size_, prefix):
+def size_as_bytes(size: float, prefix: str) -> int:
     """
     >>> size_as_bytes(7.5, 'T')
     8246337208320
@@ -88,23 +88,19 @@ def size_as_bytes(size_, prefix):
 
     exponent = si_prefixes.index(prefix) + 1
 
-    return int(size_ * (1024.0 ** exponent))
+    return int(size * (1024.0 ** exponent))
 
 
-WALEConfig = namedtuple(
-    'WALEConfig',
-    [
-        'env_dir',
-        'threshold_mb',
-        'threshold_pct',
-        'cmd',
-    ]
-)
+class WALEConfig(NamedTuple):
+    env_dir: str
+    threshold_mb: int
+    threshold_pct: int
+    cmd: List[str]
 
 
 class WALERestore(object):
-    def __init__(self, scope, datadir, connstring, env_dir, threshold_mb,
-                 threshold_pct, use_iam, no_leader, retries):
+    def __init__(self, scope: str, datadir: str, connstring: str, env_dir: str, threshold_mb: int,
+                 threshold_pct: int, use_iam: int, no_leader: bool, retries: int) -> None:
         self.scope = scope
         self.leader_connection = connstring
         self.data_dir = datadir
@@ -129,7 +125,7 @@ class WALERestore(object):
         self.init_error = (not os.path.exists(self.wal_e.env_dir))
         self.retries = retries
 
-    def run(self):
+    def run(self) -> int:
         """
         Creates a new replica using WAL-E
 
@@ -158,7 +154,7 @@ class WALERestore(object):
             logger.exception("Unhandled exception when running WAL-E restore")
         return ExitCode.FAIL
 
-    def should_use_s3_to_create_replica(self):
+    def should_use_s3_to_create_replica(self) -> Optional[bool]:
         """ determine whether it makes sense to use S3 and not pg_basebackup """
 
         threshold_megabytes = self.wal_e.threshold_mb
@@ -218,7 +214,7 @@ class WALERestore(object):
                 try:
                     # get the difference in bytes between the current WAL location and the backup start offset
                     con = psycopg.connect(self.leader_connection)
-                    if con.server_version >= 100000:
+                    if getattr(con, 'server_version', 0) >= 100000:
                         wal_name = 'wal'
                         lsn_name = 'lsn'
                     else:
@@ -232,8 +228,9 @@ class WALERestore(object):
                                      " ELSE pg_catalog.pg_{0}_{1}_diff(pg_catalog.pg_current_{0}_{1}(), %s)::bigint"
                                      " END").format(wal_name, lsn_name),
                                     (backup_start_lsn, backup_start_lsn, backup_start_lsn))
-
-                        diff_in_bytes = int(cur.fetchone()[0])
+                        for row in cur:
+                            diff_in_bytes = int(row[0])
+                            break
                 except psycopg.Error:
                     logger.exception('could not determine difference with the leader location')
                     if attempts_no < self.retries:  # retry in case of a temporarily connection issue
@@ -262,11 +259,11 @@ class WALERestore(object):
         are_thresholds_ok = is_size_thresh_ok and is_percentage_thresh_ok
 
         class Size(object):
-            def __init__(self, n_bytes, prefix=None):
+            def __init__(self, n_bytes: float, prefix: Optional[str] = None) -> None:
                 self.n_bytes = n_bytes
                 self.prefix = prefix
 
-            def __repr__(self):
+            def __repr__(self) -> str:
                 if self.prefix is not None:
                     n_bytes = size_as_bytes(self.n_bytes, self.prefix)
                 else:
@@ -274,10 +271,10 @@ class WALERestore(object):
                 return repr_size(n_bytes)
 
         class HumanContext(object):
-            def __init__(self, items):
+            def __init__(self, items: List[Tuple[str, Any]]) -> None:
                 self.items = items
 
-            def __repr__(self):
+            def __repr__(self) -> str:
                 return ', '.join('{}={!r}'.format(key, value)
                                  for key, value in self.items)
 
@@ -298,7 +295,7 @@ class WALERestore(object):
             logger.info('Thresholds are OK, using wal-e basebackup: %s', human_context)
         return are_thresholds_ok
 
-    def fix_subdirectory_path_if_broken(self, dirname):
+    def fix_subdirectory_path_if_broken(self, dirname: str) -> bool:
         # in case it is a symlink pointing to a non-existing location, remove it and create the actual directory
         path = os.path.join(self.data_dir, dirname)
         if not os.path.exists(path):
@@ -316,7 +313,7 @@ class WALERestore(object):
                 return False
         return True
 
-    def create_replica_with_s3(self):
+    def create_replica_with_s3(self) -> int:
         # if we're set up, restore the replica using fetch latest
         try:
             cmd = self.wal_e.cmd + ['backup-fetch',
@@ -334,7 +331,7 @@ class WALERestore(object):
         return exit_code
 
 
-def main():
+def main() -> int:
     logging.basicConfig(format='%(asctime)s %(levelname)s: %(message)s', level=logging.INFO)
     parser = argparse.ArgumentParser(description='Script to image replicas using WAL-E')
     parser.add_argument('--scope', required=True)
@@ -363,11 +360,13 @@ def main():
                               threshold_pct=args.threshold_backup_size_percentage, use_iam=args.use_iam,
                               no_leader=args.no_leader, retries=args.retries)
         exit_code = restore.run()
-        if not exit_code == ExitCode.RETRY_LATER:  # only WAL-E failures lead to the retry
+        if exit_code != ExitCode.RETRY_LATER:  # only WAL-E failures lead to the retry
             logger.debug('exit_code is %r, not retrying', exit_code)
             break
         time.sleep(RETRY_SLEEP_INTERVAL)
 
+    if TYPE_CHECKING:  # pragma: no cover
+        assert exit_code is not None
     return exit_code
 
 

patroni/version.py

@@ -2,4 +2,4 @@
 
 :var __version__: the current Patroni version.
 """
-__version__ = '3.0.2'
+__version__ = '3.1.2'

patroni/watchdog/base.py

@@ -4,7 +4,10 @@ import platform
 import sys
 from threading import RLock
 
-from patroni.exceptions import WatchdogError
+from typing import Any, Callable, Dict, Optional, Union
+
+from ..config import Config
+from ..exceptions import WatchdogError
 
 __all__ = ['WatchdogError', 'Watchdog']
 
@@ -15,10 +18,10 @@ MODE_AUTOMATIC = 'automatic'  # Will use a watchdog if one is available
 MODE_OFF = 'off'              # Will not try to use a watchdog
 
 
-def parse_mode(mode):
+def parse_mode(mode: Union[bool, str]) -> str:
     if mode is False:
         return MODE_OFF
-    mode = mode.lower()
+    mode = str(mode).lower()
     if mode in ['require', 'required']:
         return MODE_REQUIRED
     elif mode in ['auto', 'automatic']:
@@ -29,33 +32,35 @@ def parse_mode(mode):
         return MODE_OFF
 
 
-def synchronized(func):
-    def wrapped(self, *args, **kwargs):
-        with self._lock:
+def synchronized(func: Callable[..., Any]) -> Callable[..., Any]:
+    def wrapped(self: 'Watchdog', *args: Any, **kwargs: Any) -> Any:
+        with self.lock:
             return func(self, *args, **kwargs)
     return wrapped
 
 
 class WatchdogConfig(object):
     """Helper to contain a snapshot of configuration"""
-    def __init__(self, config):
-        self.mode = parse_mode(config['watchdog'].get('mode', 'automatic'))
+    def __init__(self, config: Config) -> None:
+        watchdog_config = config.get("watchdog") or {'mode': 'automatic'}
+
+        self.mode = parse_mode(watchdog_config.get('mode', 'automatic'))
         self.ttl = config['ttl']
         self.loop_wait = config['loop_wait']
-        self.safety_margin = config['watchdog'].get('safety_margin', 5)
-        self.driver = config['watchdog'].get('driver', 'default')
-        self.driver_config = dict((k, v) for k, v in config['watchdog'].items()
+        self.safety_margin = watchdog_config.get('safety_margin', 5)
+        self.driver = watchdog_config.get('driver', 'default')
+        self.driver_config = dict((k, v) for k, v in watchdog_config.items()
                                   if k not in ['mode', 'safety_margin', 'driver'])
 
-    def __eq__(self, other):
+    def __eq__(self, other: Any) -> bool:
         return isinstance(other, WatchdogConfig) and \
             all(getattr(self, attr) == getattr(other, attr) for attr in
                 ['mode', 'ttl', 'loop_wait', 'safety_margin', 'driver', 'driver_config'])
 
-    def __ne__(self, other):
+    def __ne__(self, other: Any) -> bool:
         return not self == other
 
-    def get_impl(self):
+    def get_impl(self) -> 'WatchdogBase':
         if self.driver == 'testing':  # pragma: no cover
             from patroni.watchdog.linux import TestingWatchdogDevice
             return TestingWatchdogDevice.from_config(self.driver_config)
@@ -66,14 +71,14 @@ class WatchdogConfig(object):
             return NullWatchdog()
 
     @property
-    def timeout(self):
+    def timeout(self) -> int:
         if self.safety_margin == -1:
             return int(self.ttl // 2)
         else:
             return self.ttl - self.safety_margin
 
     @property
-    def timing_slack(self):
+    def timing_slack(self) -> int:
         return self.timeout - self.loop_wait
 
 
@@ -82,9 +87,10 @@ class Watchdog(object):
 
     When activation fails underlying implementation will be switched to a Null implementation. To avoid log spam
     activation will only be retried when watchdog configuration is changed."""
-    def __init__(self, config):
-        self.active_config = self.config = WatchdogConfig(config)
-        self._lock = RLock()
+    def __init__(self, config: Config) -> None:
+        self.config = WatchdogConfig(config)
+        self.active_config: WatchdogConfig = self.config
+        self.lock = RLock()
         self.active = False
 
         if self.config.mode == MODE_OFF:
@@ -96,7 +102,7 @@ class Watchdog(object):
                 sys.exit(1)
 
     @synchronized
-    def reload_config(self, config):
+    def reload_config(self, config: Config) -> None:
         self.config = WatchdogConfig(config)
         # Turning a watchdog off can always be done immediately
         if self.config.mode == MODE_OFF:
@@ -113,7 +119,7 @@ class Watchdog(object):
             self.active_config = self.config
 
     @synchronized
-    def activate(self):
+    def activate(self) -> bool:
         """Activates the watchdog device with suitable timeouts. While watchdog is active keepalive needs
         to be called every time loop_wait expires.
 
@@ -122,7 +128,7 @@ class Watchdog(object):
         self.active = True
         return self._activate()
 
-    def _activate(self):
+    def _activate(self) -> bool:
         self.active_config = self.config
 
         if self.config.timing_slack < 0:
@@ -136,12 +142,13 @@ class Watchdog(object):
         except WatchdogError as e:
             logger.warning("Could not activate %s: %s", self.impl.describe(), e)
             self.impl = NullWatchdog()
+            actual_timeout = self.impl.get_timeout()
 
         if self.impl.is_running and not self.impl.can_be_disabled:
             logger.warning("Watchdog implementation can't be disabled."
                            " Watchdog will trigger after Patroni loses leader key.")
 
-        if not self.impl.is_running or actual_timeout > self.config.timeout:
+        if not self.impl.is_running or actual_timeout and actual_timeout > self.config.timeout:
             if self.config.mode == MODE_REQUIRED:
                 if self.impl.is_null:
                     logger.error("Configuration requires watchdog, but watchdog could not be configured.")
@@ -165,7 +172,7 @@ class Watchdog(object):
 
         return True
 
-    def _set_timeout(self):
+    def _set_timeout(self) -> Optional[int]:
         if self.impl.has_set_timeout():
             self.impl.set_timeout(self.config.timeout)
 
@@ -182,11 +189,11 @@ class Watchdog(object):
         return actual_timeout
 
     @synchronized
-    def disable(self):
+    def disable(self) -> None:
         self._disable()
         self.active = False
 
-    def _disable(self):
+    def _disable(self) -> None:
         try:
             if self.impl.is_running and not self.impl.can_be_disabled:
                 # Give sysadmin some extra time to clean stuff up.
@@ -198,7 +205,7 @@ class Watchdog(object):
             logger.error("Error while disabling watchdog: %s", e)
 
     @synchronized
-    def keepalive(self):
+    def keepalive(self) -> None:
         try:
             if self.active:
                 self.impl.keepalive()
@@ -223,12 +230,12 @@ class Watchdog(object):
 
     @property
     @synchronized
-    def is_running(self):
+    def is_running(self) -> bool:
         return self.impl.is_running
 
     @property
     @synchronized
-    def is_healthy(self):
+    def is_healthy(self) -> bool:
         if self.config.mode != MODE_REQUIRED:
             return True
         return self.config.timing_slack >= 0 and self.impl.is_healthy
@@ -240,60 +247,59 @@ class WatchdogBase(abc.ABC):
     is_null = False
 
     @property
-    def is_running(self):
+    def is_running(self) -> bool:
         """Returns True when watchdog is activated and capable of performing it's task."""
         return False
 
     @property
-    def is_healthy(self):
+    def is_healthy(self) -> bool:
         """Returns False when calling open() is known to fail."""
         return False
 
     @property
-    def can_be_disabled(self):
+    def can_be_disabled(self) -> bool:
         """Returns True when watchdog will be disabled by calling close(). Some watchdog devices
         will keep running no matter what once activated. May raise WatchdogError if called without
         calling open() first."""
         return True
 
     @abc.abstractmethod
-    def open(self):
+    def open(self) -> None:
         """Open watchdog device.
 
         When watchdog is opened keepalive must be called. Returns nothing on success
         or raises WatchdogError if the device could not be opened."""
 
     @abc.abstractmethod
-    def close(self):
+    def close(self) -> None:
         """Gracefully close watchdog device."""
 
     @abc.abstractmethod
-    def keepalive(self):
+    def keepalive(self) -> None:
         """Resets the watchdog timer.
 
         Watchdog must be open when keepalive is called."""
 
     @abc.abstractmethod
-    def get_timeout(self):
+    def get_timeout(self) -> int:
         """Returns the current keepalive timeout in effect."""
 
-    @staticmethod
-    def has_set_timeout():
+    def has_set_timeout(self) -> bool:
         """Returns True if setting a timeout is supported."""
         return False
 
-    def set_timeout(self, timeout):
+    def set_timeout(self, timeout: int) -> None:
         """Set the watchdog timer timeout.
 
         :param timeout: watchdog timeout in seconds"""
         raise WatchdogError("Setting timeout is not supported on {0}".format(self.describe()))
 
-    def describe(self):
+    def describe(self) -> str:
         """Human readable name for this device"""
         return self.__class__.__name__
 
     @classmethod
-    def from_config(cls, config):
+    def from_config(cls, config: Dict[str, Any]) -> 'WatchdogBase':
         return cls()
 
 
@@ -301,15 +307,15 @@ class NullWatchdog(WatchdogBase):
     """Null implementation when watchdog is not supported."""
     is_null = True
 
-    def open(self):
+    def open(self) -> None:
         return
 
-    def close(self):
+    def close(self) -> None:
         return
 
-    def keepalive(self):
+    def keepalive(self) -> None:
         return
 
-    def get_timeout(self):
+    def get_timeout(self) -> int:
         # A big enough number to not matter
         return 1000000000

patroni/watchdog/linux.py

@@ -1,8 +1,11 @@
-import collections
+# pyright: reportConstantRedefinition=false
 import ctypes
 import os
 import platform
-from patroni.watchdog.base import WatchdogBase, WatchdogError
+
+from typing import Any, Dict, NamedTuple
+
+from .base import WatchdogBase, WatchdogError
 
 # Pythonification of linux/ioctl.h
 IOC_NONE = 0
@@ -19,7 +22,7 @@ machine = platform.machine()
 if machine in ['mips', 'sparc', 'powerpc', 'ppc64', 'ppc64le']:  # pragma: no cover
     IOC_SIZEBITS = 13
     IOC_DIRBITS = 3
-    IOC_NONE, IOC_WRITE, IOC_READ = 1, 4, 2
+    IOC_NONE, IOC_WRITE = 1, 4
 elif machine == 'parisc':  # pragma: no cover
     IOC_WRITE, IOC_READ = 2, 1
 
@@ -29,19 +32,19 @@ IOC_SIZESHIFT = IOC_TYPESHIFT + IOC_TYPEBITS
 IOC_DIRSHIFT = IOC_SIZESHIFT + IOC_SIZEBITS
 
 
-def IOW(type_, nr, size):
+def IOW(type_: str, nr: int, size: int) -> int:
     return IOC(IOC_WRITE, type_, nr, size)
 
 
-def IOR(type_, nr, size):
+def IOR(type_: str, nr: int, size: int) -> int:
     return IOC(IOC_READ, type_, nr, size)
 
 
-def IOWR(type_, nr, size):
+def IOWR(type_: str, nr: int, size: int) -> int:
     return IOC(IOC_READ | IOC_WRITE, type_, nr, size)
 
 
-def IOC(dir_, type_, nr, size):
+def IOC(dir_: int, type_: str, nr: int, size: int) -> int:
     return (dir_ << IOC_DIRSHIFT) \
         | (ord(type_) << IOC_TYPESHIFT) \
         | (nr << IOC_NRSHIFT) \
@@ -104,9 +107,13 @@ WDIOS = {
 # Implementation
 
 
-class WatchdogInfo(collections.namedtuple('WatchdogInfo', 'options,version,identity')):
+class WatchdogInfo(NamedTuple):
     """Watchdog descriptor from the kernel"""
-    def __getattr__(self, name):
+    options: int
+    version: int
+    identity: str
+
+    def __getattr__(self, name: str) -> bool:
         """Convenience has_XYZ attributes for checking WDIOF bits in options"""
         if name.startswith('has_') and name[4:] in WDIOF:
             return bool(self.options & WDIOF[name[4:]])
@@ -117,32 +124,32 @@ class WatchdogInfo(collections.namedtuple('WatchdogInfo', 'options,version,ident
 class LinuxWatchdogDevice(WatchdogBase):
     DEFAULT_DEVICE = '/dev/watchdog'
 
-    def __init__(self, device):
+    def __init__(self, device: str) -> None:
         self.device = device
         self._support_cache = None
         self._fd = None
 
     @classmethod
-    def from_config(cls, config):
+    def from_config(cls, config: Dict[str, Any]) -> 'LinuxWatchdogDevice':
         device = config.get('device', cls.DEFAULT_DEVICE)
         return cls(device)
 
     @property
-    def is_running(self):
+    def is_running(self) -> bool:
         return self._fd is not None
 
     @property
-    def is_healthy(self):
+    def is_healthy(self) -> bool:
         return os.path.exists(self.device) and os.access(self.device, os.W_OK)
 
-    def open(self):
+    def open(self) -> None:
         try:
             self._fd = os.open(self.device, os.O_WRONLY)
         except OSError as e:
             raise WatchdogError("Can't open watchdog device: {0}".format(e))
 
-    def close(self):
-        if self.is_running:
+    def close(self) -> None:
+        if self._fd is not None:  # self.is_running
             try:
                 os.write(self._fd, b'V')
                 os.close(self._fd)
@@ -151,10 +158,10 @@ class LinuxWatchdogDevice(WatchdogBase):
                 raise WatchdogError("Error while closing {0}: {1}".format(self.describe(), e))
 
     @property
-    def can_be_disabled(self):
+    def can_be_disabled(self) -> bool:
         return self.get_support().has_MAGICCLOSE
 
-    def _ioctl(self, func, arg):
+    def _ioctl(self, func: int, arg: Any) -> None:
         """Runs the specified ioctl on the underlying fd.
 
         Raises WatchdogError if the device is closed.
@@ -165,7 +172,7 @@ class LinuxWatchdogDevice(WatchdogBase):
             import fcntl
             fcntl.ioctl(self._fd, func, arg, True)
 
-    def get_support(self):
+    def get_support(self) -> WatchdogInfo:
         if self._support_cache is None:
             info = watchdog_info()
             try:
@@ -177,7 +184,7 @@ class LinuxWatchdogDevice(WatchdogBase):
                                                bytearray(info.identity).decode(errors='ignore').rstrip('\x00'))
         return self._support_cache
 
-    def describe(self):
+    def describe(self) -> str:
         dev_str = " at {0}".format(self.device) if self.device != self.DEFAULT_DEVICE else ""
         ver_str = ""
         identity = "Linux watchdog device"
@@ -190,17 +197,19 @@ class LinuxWatchdogDevice(WatchdogBase):
 
         return identity + ver_str + dev_str
 
-    def keepalive(self):
+    def keepalive(self) -> None:
+        if self._fd is None:
+            raise WatchdogError("Watchdog device is closed")
         try:
             os.write(self._fd, b'1')
         except OSError as e:
             raise WatchdogError("Could not send watchdog keepalive: {0}".format(e))
 
-    def has_set_timeout(self):
+    def has_set_timeout(self) -> bool:
         """Returns True if setting a timeout is supported."""
         return self.get_support().has_SETTIMEOUT
 
-    def set_timeout(self, timeout):
+    def set_timeout(self, timeout: int) -> None:
         timeout = int(timeout)
         if not 0 < timeout < 0xFFFF:
             raise WatchdogError("Invalid timeout {0}. Supported values are between 1 and 65535".format(timeout))
@@ -209,7 +218,7 @@ class LinuxWatchdogDevice(WatchdogBase):
         except (WatchdogError, OSError, IOError) as e:
             raise WatchdogError("Could not set timeout on watchdog device: {}".format(e))
 
-    def get_timeout(self):
+    def get_timeout(self) -> int:
         timeout = ctypes.c_int()
         try:
             self._ioctl(WDIOC_GETTIMEOUT, timeout)
@@ -222,14 +231,16 @@ class TestingWatchdogDevice(LinuxWatchdogDevice):  # pragma: no cover
     """Converts timeout ioctls to regular writes that can be intercepted from a named pipe."""
     timeout = 60
 
-    def get_support(self):
+    def get_support(self) -> WatchdogInfo:
         return WatchdogInfo(WDIOF['MAGICCLOSE'] | WDIOF['SETTIMEOUT'], 0, "Watchdog test harness")
 
-    def set_timeout(self, timeout):
+    def set_timeout(self, timeout: int) -> None:
+        if self._fd is None:
+            raise WatchdogError("Watchdog device is closed")
         buf = "Ctimeout={0}\n".format(timeout).encode('utf8')
         while len(buf):
             buf = buf[os.write(self._fd, buf):]
         self.timeout = timeout
 
-    def get_timeout(self):
+    def get_timeout(self) -> int:
         return self.timeout

postgres0.yml

@@ -59,6 +59,13 @@ bootstrap:
       #primary_slot_name: patroni
     postgresql:
       use_pg_rewind: true
+      pg_hba:
+      # For kerberos gss based connectivity (discard @.*$)
+      #- host replication replicator 127.0.0.1/32 gss include_realm=0
+      #- host all all 0.0.0.0/0 gss include_realm=0
+      - host replication replicator 127.0.0.1/32 md5
+      - host all all 0.0.0.0/0 md5
+      #  - hostssl all all 0.0.0.0/0 md5
 #      use_slots: true
       parameters:
 #        wal_level: hot_standby
@@ -83,18 +90,10 @@ bootstrap:
   - encoding: UTF8
   - data-checksums
 
-  pg_hba:  # Add following lines to pg_hba.conf after running 'initdb'
-  # For kerberos gss based connectivity (discard @.*$)
-  #- host replication replicator 127.0.0.1/32 gss include_realm=0
-  #- host all all 0.0.0.0/0 gss include_realm=0
-  - host replication replicator 127.0.0.1/32 md5
-  - host all all 0.0.0.0/0 md5
-#  - hostssl all all 0.0.0.0/0 md5
-
   # Additional script to be launched after initial cluster creation (will be passed the connection URL as parameter)
 # post_init: /usr/local/bin/setup_cluster.sh
 
-  # Some additional users users which needs to be created after initializing new cluster
+  # Some additional users which needs to be created after initializing new cluster
   users:
     admin:
       password: admin%

postgres1.yml

@@ -53,6 +53,13 @@ bootstrap:
     maximum_lag_on_failover: 1048576
     postgresql:
       use_pg_rewind: true
+      pg_hba:
+      # For kerberos gss based connectivity (discard @.*$)
+      #- host replication replicator 127.0.0.1/32 gss include_realm=0
+      #- host all all 0.0.0.0/0 gss include_realm=0
+      - host replication replicator 127.0.0.1/32 md5
+      - host all all 0.0.0.0/0 md5
+      #  - hostssl all all 0.0.0.0/0 md5
 #      use_slots: true
       parameters:
 #        wal_level: hot_standby
@@ -77,18 +84,10 @@ bootstrap:
   - encoding: UTF8
   - data-checksums
 
-  pg_hba:  # Add following lines to pg_hba.conf after running 'initdb'
-  # For kerberos gss based connectivity (discard @.*$)
-  #- host replication replicator 127.0.0.1/32 gss include_realm=0
-  #- host all all 0.0.0.0/0 gss include_realm=0
-  - host replication replicator 127.0.0.1/32 md5
-  - host all all 0.0.0.0/0 md5
-#  - hostssl all all 0.0.0.0/0 md5
-
   # Additional script to be launched after initial cluster creation (will be passed the connection URL as parameter)
 # post_init: /usr/local/bin/setup_cluster.sh
 
-  # Some additional users users which needs to be created after initializing new cluster
+  # Some additional users which needs to be created after initializing new cluster
   users:
     admin:
       password: admin%

postgres2.yml

@@ -53,6 +53,13 @@ bootstrap:
     maximum_lag_on_failover: 1048576
     postgresql:
       use_pg_rewind: true
+      pg_hba:
+      # For kerberos gss based connectivity (discard @.*$)
+      #- host replication replicator 127.0.0.1/32 gss include_realm=0
+      #- host all all 0.0.0.0/0 gss include_realm=0
+      - host replication replicator 127.0.0.1/32 md5
+      - host all all 0.0.0.0/0 md5
+      #  - hostssl all all 0.0.0.0/0 md5
 #      use_slots: true
       parameters:
 #        wal_level: hot_standby
@@ -77,15 +84,7 @@ bootstrap:
   - encoding: UTF8
   - data-checksums
 
-  pg_hba:  # Add following lines to pg_hba.conf after running 'initdb'
-  # For kerberos gss based connectivity (discard @.*$)
-  #- host replication replicator 127.0.0.1/32 gss include_realm=0
-  #- host all all 0.0.0.0/0 gss include_realm=0
-  - host replication replicator 127.0.0.1/32 md5
-  - host all all 0.0.0.0/0 md5
-#  - hostssl all all 0.0.0.0/0 md5
-
-  # Some additional users users which needs to be created after initializing new cluster
+  # Some additional users which needs to be created after initializing new cluster
   users:
     admin:
       password: admin%
@@ -122,4 +121,4 @@ tags:
     nofailover: false
     noloadbalance: false
     clonefrom: false
-    replicatefrom: postgres1
+#    replicatefrom: postgresql1

pyrightconfig.json

@@ -0,0 +1,27 @@
+{
+  "include": [
+    "patroni"
+  ],
+
+  "exclude": [
+    "**/__pycache__"
+  ],
+
+  "ignore": [
+  ],
+
+  "defineConstant": {
+    "DEBUG": true
+  },
+
+  "stubPath": "typings/",
+
+  "reportMissingImports": true,
+  "reportMissingTypeStubs": false,
+
+  "pythonVersion": "3.11",
+  "pythonPlatform": "All",
+
+  "typeCheckingMode": "strict"
+
+}

release.sh

@@ -1,11 +1,12 @@
 #!/bin/bash
 
 # Release process:
-# 1. Open a PR that updates release notes and Patroni version
-# 2. Merge it
-# 3. Run release.sh
-# 4. After the new tag is pushed, the .github/workflows/release.yaml will run tests and upload the new package to test.pypi.org
-# 5. Once the release is created, the .github/workflows/release.yaml will run tests and upload the new package to pypi.org
+# 1. Open a PR that updates release notes, Patroni version and pyright version in the tests workflow.
+# 2. Resolve possible typing issues.
+# 3. Merge the PR.
+# 4. Run release.sh
+# 5. After the new tag is pushed, the .github/workflows/release.yaml will run tests and upload the new package to test.pypi.org
+# 6. Once the release is created, the .github/workflows/release.yaml will run tests and upload the new package to pypi.org
 
 ## Bail out on any non-zero exitcode from the called processes
 set -xe

requirements.docs.txt

@@ -0,0 +1,5 @@
+sphinx>=4
+sphinx_rtd_theme>1
+sphinxcontrib-apidoc
+sphinx-github-style
+pyyaml

setup.py

@@ -88,7 +88,7 @@ class Flake8(_Command):
                 yield package_directory
 
     def targets(self):
-        return [package for package in self.package_files()] + ['tests', 'setup.py']
+        return [package for package in self.package_files()] + ['tests', 'features', 'setup.py']
 
     def run(self):
         from flake8.main.cli import main
@@ -116,7 +116,7 @@ class PyTest(_Command):
 
 
 def read(fname):
-    with open(os.path.join(__location__, fname)) as fd:
+    with open(os.path.join(__location__, fname), encoding='utf-8') as fd:
         return fd.read()
 
 
@@ -157,7 +157,10 @@ def setup_package(version):
         long_description=read('README.rst'),
         classifiers=CLASSIFIERS,
         packages=find_packages(exclude=['tests', 'tests.*']),
-        package_data={MAIN_PACKAGE: ["*.json"]},
+        package_data={MAIN_PACKAGE: [
+            "postgresql/available_parameters/*.yml",
+            "postgresql/available_parameters/*.yaml",
+        ]},
         install_requires=install_requires,
         extras_require=EXTRAS_REQUIRE,
         cmdclass=cmdclass,

tests/__init__.py

@@ -3,7 +3,7 @@ import os
 import shutil
 import unittest
 
-from mock import Mock, patch
+from mock import Mock, PropertyMock, patch
 
 import urllib3
 
@@ -19,10 +19,20 @@ class SleepException(Exception):
     pass
 
 
+mock_available_gucs = PropertyMock(return_value={
+    'cluster_name', 'constraint_exclusion', 'force_parallel_mode', 'hot_standby', 'listen_addresses', 'max_connections',
+    'max_locks_per_transaction', 'max_prepared_transactions', 'max_replication_slots', 'max_stack_depth',
+    'max_wal_senders', 'max_worker_processes', 'port', 'search_path', 'shared_preload_libraries',
+    'stats_temp_directory', 'synchronous_standby_names', 'track_commit_timestamp', 'unix_socket_directories',
+    'vacuum_cost_delay', 'vacuum_cost_limit', 'wal_keep_size', 'wal_level', 'wal_log_hints', 'zero_damaged_pages',
+})
+
+
 class MockResponse(object):
 
     def __init__(self, status_code=200):
         self.status_code = status_code
+        self.headers = {'content-type': 'json'}
         self.content = '{}'
         self.reason = 'Not Found'
 
@@ -38,10 +48,6 @@ class MockResponse(object):
     def getheader(*args):
         return ''
 
-    @staticmethod
-    def getheaders():
-        return {'content-type': 'json'}
-
 
 def requests_get(url, method='GET', endpoint=None, data='', **kwargs):
     members = '[{"id":14855829450254237642,"peerURLs":["http://localhost:2380","http://localhost:7001"],' +\
@@ -85,6 +91,8 @@ class MockCursor(object):
         self.description = [Mock()]
 
     def execute(self, sql, *params):
+        if isinstance(sql, bytes):
+            sql = sql.decode('utf-8')
         if sql.startswith('blabla'):
             raise psycopg.ProgrammingError()
         elif sql == 'CHECKPOINT' or sql.startswith('SELECT pg_catalog.pg_create_'):
@@ -98,9 +106,9 @@ class MockCursor(object):
         elif sql.startswith('SELECT slot_name'):
             self.results = [('blabla', 'physical'), ('foobar', 'physical'), ('ls', 'logical', 'a', 'b', 5, 100, 500)]
         elif sql.startswith('WITH slots AS (SELECT slot_name, active'):
-            self.results = [(False, True)]
+            self.results = [(False, True)] if self.rowcount == 1 else [None]
         elif sql.startswith('SELECT CASE WHEN pg_catalog.pg_is_in_recovery()'):
-            self.results = [(1, 2, 1, 0, False, 1, 1, None, None,
+            self.results = [(1, 2, 1, 0, False, 1, 1, None, None, 'streaming', '',
                              [{"slot_name": "ls", "confirmed_flush_lsn": 12345}],
                              'on', 'n1', None)]
         elif sql.startswith('SELECT pg_catalog.pg_is_in_recovery()'):
@@ -109,12 +117,32 @@ class MockCursor(object):
             replication_info = '[{"application_name":"walreceiver","client_addr":"1.2.3.4",' +\
                                '"state":"streaming","sync_state":"async","sync_priority":0}]'
             now = datetime.datetime.now(tzutc)
-            self.results = [(now, 0, '', 0, '', False, now, replication_info)]
+            self.results = [(now, 0, '', 0, '', False, now, 'streaming', None, replication_info)]
+        elif sql.startswith('SELECT name, pg_catalog.current_setting(name) FROM pg_catalog.pg_settings'):
+            self.results = [('data_directory', 'data'),
+                            ('hba_file', os.path.join('data', 'pg_hba.conf')),
+                            ('ident_file', os.path.join('data', 'pg_ident.conf')),
+                            ('max_connections', 42),
+                            ('max_locks_per_transaction', 73),
+                            ('max_prepared_transactions', 0),
+                            ('max_replication_slots', 21),
+                            ('max_wal_senders', 37),
+                            ('track_commit_timestamp', 'off'),
+                            ('wal_level', 'replica'),
+                            ('listen_addresses', '6.6.6.6'),
+                            ('port', 1984),
+                            ('archive_command', 'my archive command'),
+                            ('cluster_name', 'my_cluster')]
         elif sql.startswith('SELECT name, setting'):
             self.results = [('wal_segment_size', '2048', '8kB', 'integer', 'internal'),
                             ('wal_block_size', '8192', None, 'integer', 'internal'),
                             ('shared_buffers', '16384', '8kB', 'integer', 'postmaster'),
                             ('wal_buffers', '-1', '8kB', 'integer', 'postmaster'),
+                            ('max_connections', '100', None, 'integer', 'postmaster'),
+                            ('max_prepared_transactions', '0', None, 'integer', 'postmaster'),
+                            ('max_worker_processes', '8', None, 'integer', 'postmaster'),
+                            ('max_locks_per_transaction', '64', None, 'integer', 'postmaster'),
+                            ('max_wal_senders', '5', None, 'integer', 'postmaster'),
                             ('search_path', 'public', None, 'string', 'user'),
                             ('port', '5433', None, 'integer', 'postmaster'),
                             ('listen_addresses', '*', None, 'string', 'postmaster'),
@@ -214,6 +242,7 @@ class PostgresInit(unittest.TestCase):
 
 class BaseTestPostgresql(PostgresInit):
 
+    @patch('time.sleep', Mock())
     def setUp(self):
         super(BaseTestPostgresql, self).setUp()
 

tests/test_api.py

@@ -11,6 +11,7 @@ from mock import Mock, PropertyMock, patch
 from socketserver import ThreadingMixIn
 
 from patroni.api import RestApiHandler, RestApiServer
+from patroni.config import GlobalConfig
 from patroni.dcs import ClusterConfig, Member
 from patroni.ha import _MemberStatus
 from patroni.utils import tzutc
@@ -28,7 +29,8 @@ class MockPostgresql(object):
     name = 'test'
     state = 'running'
     role = 'primary'
-    server_version = '999999'
+    server_version = 90625
+    major_version = 90600
     sysid = 'dummysysid'
     scope = 'dummy'
     pending_restart = True
@@ -54,6 +56,10 @@ class MockPostgresql(object):
     def is_running():
         return True
 
+    @staticmethod
+    def replication_state_from_parameters(*args):
+        return 'streaming'
+
 
 class MockWatchdog(object):
     is_healthy = False
@@ -116,10 +122,6 @@ class MockHa(object):
     def is_paused():
         return True
 
-    @staticmethod
-    def is_standby_cluster():
-        return False
-
 
 class MockLogger(object):
 
@@ -128,10 +130,16 @@ class MockLogger(object):
     records_lost = 1
 
 
+class MockConfig(object):
+
+    def get_global_config(self, _):
+        return GlobalConfig({})
+
+
 class MockPatroni(object):
 
     ha = MockHa()
-    config = Mock()
+    config = MockConfig()
     postgresql = ha.state_handler
     dcs = Mock()
     logger = MockLogger()
@@ -185,7 +193,8 @@ class TestRestApiHandler(unittest.TestCase):
     def test_do_GET(self):
         MockPatroni.dcs.cluster.last_lsn = 20
         MockPatroni.dcs.cluster.sync.members = [MockPostgresql.name]
-        MockRestApiServer(RestApiHandler, 'GET /replica')
+        with patch.object(GlobalConfig, 'is_synchronous_mode', PropertyMock(return_value=True)):
+            MockRestApiServer(RestApiHandler, 'GET /replica')
         MockRestApiServer(RestApiHandler, 'GET /replica?lag=1M')
         MockRestApiServer(RestApiHandler, 'GET /replica?lag=10MB')
         MockRestApiServer(RestApiHandler, 'GET /replica?lag=10485760')
@@ -207,7 +216,7 @@ class TestRestApiHandler(unittest.TestCase):
         with patch.object(MockHa, 'is_leader', Mock(return_value=True)):
             MockRestApiServer(RestApiHandler, 'GET /replica')
             MockRestApiServer(RestApiHandler, 'GET /read-only-sync')
-            with patch.object(MockHa, 'is_standby_cluster', Mock(return_value=True)):
+            with patch.object(GlobalConfig, 'is_standby_cluster', Mock(return_value=True)):
                 MockRestApiServer(RestApiHandler, 'GET /standby_leader')
         MockPatroni.dcs.cluster = None
         with patch.object(RestApiHandler, 'get_postgresql_status', Mock(return_value={'role': 'primary'})):
@@ -215,9 +224,10 @@ class TestRestApiHandler(unittest.TestCase):
         with patch.object(MockHa, 'restart_scheduled', Mock(return_value=True)):
             MockRestApiServer(RestApiHandler, 'GET /primary')
         self.assertIsNotNone(MockRestApiServer(RestApiHandler, 'GET /primary'))
-        with patch.object(RestApiServer, 'query', Mock(return_value=[('', 1, '', '', '', '', False, '')])):
+        with patch.object(RestApiServer, 'query', Mock(return_value=[('', 1, '', '', '', '', False, None, None, '')])):
             self.assertIsNotNone(MockRestApiServer(RestApiHandler, 'GET /patroni'))
-        with patch.object(MockHa, 'is_standby_cluster', Mock(return_value=True)):
+        with patch.object(GlobalConfig, 'is_standby_cluster', Mock(return_value=True)), \
+                patch.object(GlobalConfig, 'is_paused', Mock(return_value=True)):
             MockRestApiServer(RestApiHandler, 'GET /standby_leader')
 
         # test tags
@@ -393,8 +403,8 @@ class TestRestApiHandler(unittest.TestCase):
         with patch.object(MockHa, 'is_failsafe_mode', Mock(return_value=False), create=True):
             self.assertIsNotNone(MockRestApiServer(RestApiHandler, 'POST /failsafe HTTP/1.0' + self._authorization))
         with patch.object(MockHa, 'is_failsafe_mode', Mock(return_value=True), create=True):
-            self.assertIsNotNone(MockRestApiServer(RestApiHandler, 'POST /failsafe HTTP/1.0' + self._authorization +
-                                                                   '\nContent-Length: 9\n\n{"a":"b"}'))
+            self.assertIsNotNone(MockRestApiServer(RestApiHandler, 'POST /failsafe HTTP/1.0' + self._authorization
+                                                   + '\nContent-Length: 9\n\n{"a":"b"}'))
 
     @patch.object(MockPatroni, 'sighup_handler', Mock())
     def test_do_POST_reload(self):
@@ -405,9 +415,7 @@ class TestRestApiHandler(unittest.TestCase):
     def test_do_POST_sigterm(self):
         self.assertIsNotNone(MockRestApiServer(RestApiHandler, 'POST /sigterm HTTP/1.0' + self._authorization))
 
-    @patch.object(MockPatroni, 'dcs')
-    def test_do_POST_restart(self, mock_dcs):
-        mock_dcs.get_cluster.return_value.is_paused.return_value = False
+    def test_do_POST_restart(self):
         request = 'POST /restart HTTP/1.0' + self._authorization
         self.assertIsNotNone(MockRestApiServer(RestApiHandler, request))
 
@@ -449,12 +457,12 @@ class TestRestApiHandler(unittest.TestCase):
                 request = make_request(role='primary', postgres_version='9.5.2')
                 MockRestApiServer(RestApiHandler, request)
 
-        mock_dcs.get_cluster.return_value.is_paused.return_value = True
-        MockRestApiServer(RestApiHandler, make_request(schedule='2016-08-42 12:45TZ+1', role='primary'))
-        # Valid timeout
-        MockRestApiServer(RestApiHandler, make_request(timeout='60s'))
-        # Invalid timeout
-        MockRestApiServer(RestApiHandler, make_request(timeout='42towels'))
+        with patch.object(GlobalConfig, 'is_paused', PropertyMock(return_value=True)):
+            MockRestApiServer(RestApiHandler, make_request(schedule='2016-08-42 12:45TZ+1', role='primary'))
+            # Valid timeout
+            MockRestApiServer(RestApiHandler, make_request(timeout='60s'))
+            # Invalid timeout
+            MockRestApiServer(RestApiHandler, make_request(timeout='42towels'))
 
     def test_do_DELETE_restart(self):
         for retval in (True, False):
@@ -471,10 +479,7 @@ class TestRestApiHandler(unittest.TestCase):
         mock_dcs.get_cluster.return_value.failover = None
         self.assertIsNotNone(MockRestApiServer(RestApiHandler, request))
 
-    @patch.object(MockPatroni, 'dcs')
-    def test_do_POST_reinitialize(self, mock_dcs):
-        cluster = mock_dcs.get_cluster.return_value
-        cluster.is_paused.return_value = False
+    def test_do_POST_reinitialize(self):
         request = 'POST /reinitialize HTTP/1.0' + self._authorization + '\nContent-Length: 15\n\n{"force": true}'
         MockRestApiServer(RestApiHandler, request)
         with patch.object(MockHa, 'reinitialize', Mock(return_value=None)):
@@ -492,8 +497,6 @@ class TestRestApiHandler(unittest.TestCase):
     def test_do_POST_switchover(self, dcs):
         dcs.loop_wait = 10
         cluster = dcs.get_cluster.return_value
-        cluster.is_synchronous_mode.return_value = False
-        cluster.is_paused.return_value = False
 
         post = 'POST /switchover HTTP/1.0' + self._authorization + '\nContent-Length: '
 
@@ -507,20 +510,22 @@ class TestRestApiHandler(unittest.TestCase):
 
         request = post + '25\n\n{"leader": "postgresql1"}'
 
-        cluster.is_paused.return_value = True
-        MockRestApiServer(RestApiHandler, request)
-
-        cluster.is_paused.return_value = False
-        for cluster.is_synchronous_mode.return_value in (True, False):
+        with patch.object(GlobalConfig, 'is_paused', PropertyMock(return_value=True)):
             MockRestApiServer(RestApiHandler, request)
 
+        for is_synchronous_mode in (True, False):
+            with patch.object(GlobalConfig, 'is_synchronous_mode', PropertyMock(return_value=is_synchronous_mode)):
+                MockRestApiServer(RestApiHandler, request)
+
         cluster.leader.name = 'postgresql2'
         request = post + '53\n\n{"leader": "postgresql1", "candidate": "postgresql2"}'
         MockRestApiServer(RestApiHandler, request)
 
         cluster.leader.name = 'postgresql1'
-        for cluster.is_synchronous_mode.return_value in (True, False):
-            MockRestApiServer(RestApiHandler, request)
+        cluster.sync.matches.return_value = False
+        for is_synchronous_mode in (True, False):
+            with patch.object(GlobalConfig, 'is_synchronous_mode', PropertyMock(return_value=is_synchronous_mode)):
+                MockRestApiServer(RestApiHandler, request)
 
         cluster.members = [Member(0, 'postgresql0', 30, {'api_url': 'http'}),
                            Member(0, 'postgresql2', 30, {'api_url': 'http'})]
@@ -554,7 +559,8 @@ class TestRestApiHandler(unittest.TestCase):
         request = post + '103\n\n{"leader": "postgresql1", "member": "postgresql2",' +\
                          ' "scheduled_at": "6016-02-15T18:13:30.568224+01:00"}'
         MockRestApiServer(RestApiHandler, request)
-        with patch.object(MockPatroni, 'dcs') as d:
+        with patch.object(GlobalConfig, 'is_paused', PropertyMock(return_value=True)), \
+                patch.object(MockPatroni, 'dcs') as d:
             d.manual_failover.return_value = False
             MockRestApiServer(RestApiHandler, request)
 
@@ -570,13 +576,11 @@ class TestRestApiHandler(unittest.TestCase):
         # Invalid date
         self.assertIsNotNone(MockRestApiServer(RestApiHandler, request + '2010-02-29T18:13:30.568224+01:00"}'))
 
-    @patch.object(MockPatroni, 'dcs', Mock())
     def test_do_POST_failover(self):
         post = 'POST /failover HTTP/1.0' + self._authorization + '\nContent-Length: '
         MockRestApiServer(RestApiHandler, post + '14\n\n{"leader":"1"}')
         MockRestApiServer(RestApiHandler, post + '37\n\n{"candidate":"2","scheduled_at": "1"}')
 
-    @patch.object(MockPatroni, 'dcs', Mock())
     @patch.object(MockHa, 'is_leader', Mock(return_value=True))
     def test_do_POST_citus(self):
         post = 'POST /citus HTTP/1.0' + self._authorization + '\nContent-Length: '
@@ -622,24 +626,38 @@ class TestRestApiServer(unittest.TestCase):
         try:
             raise Exception()
         except Exception:
-            self.assertIsNone(MockRestApiServer.handle_error(None, ('127.0.0.1', 55555)))
+            self.assertIsNone(self.srv.handle_error(None, ('127.0.0.1', 55555)))
 
     @patch.object(HTTPServer, '__init__', Mock(side_effect=socket.error))
     def test_socket_error(self):
         self.assertRaises(socket.error, MockRestApiServer, Mock(), '', {'listen': '*:8008'})
 
+    def __create_socket(self):
+        sock = socket.socket()
+        try:
+            import ssl
+            ctx = ssl.create_default_context(ssl.Purpose.SERVER_AUTH)
+            ctx.check_hostname = False
+            sock = ctx.wrap_socket(sock=sock)
+            sock.do_handshake = Mock()
+            sock.unwrap = Mock(side_effect=Exception)
+        except Exception:
+            pass
+        return sock
+
     @patch.object(ThreadingMixIn, 'process_request_thread', Mock())
     def test_process_request_thread(self):
-        self.srv.process_request_thread(Mock(), '2')
+        self.srv.process_request_thread(self.__create_socket(), ('2', 54321))
 
     @patch.object(MockRestApiServer, 'process_request', Mock(side_effect=RuntimeError))
     @patch.object(MockRestApiServer, 'get_request')
     def test_process_request_error(self, mock_get_request):
-        mock_request = Mock()
-        mock_request.unwrap.side_effect = Exception
-        mock_get_request.return_value = (mock_request, ('127.0.0.1', 55555))
+        mock_get_request.return_value = (self.__create_socket(), ('127.0.0.1', 55555))
         self.srv._handle_request_noblock()
 
     @patch('ssl._ssl._test_decode_cert', Mock())
     def test_reload_local_certificate(self):
         self.assertTrue(self.srv.reload_local_certificate())
+
+    def test_get_certificate_serial_number(self):
+        self.assertIsNone(self.srv.get_certificate_serial_number())

tests/test_bootstrap.py

@@ -1,4 +1,5 @@
 import os
+import sys
 
 from mock import Mock, PropertyMock, patch
 
@@ -8,12 +9,13 @@ from patroni.postgresql.bootstrap import Bootstrap
 from patroni.postgresql.cancellable import CancellableSubprocess
 from patroni.postgresql.config import ConfigHandler
 
-from . import psycopg_connect, BaseTestPostgresql
+from . import psycopg_connect, BaseTestPostgresql, mock_available_gucs
 
 
 @patch('subprocess.call', Mock(return_value=0))
 @patch('patroni.psycopg.connect', psycopg_connect)
 @patch('os.rename', Mock())
+@patch.object(Postgresql, 'available_gucs', mock_available_gucs)
 class TestBootstrap(BaseTestPostgresql):
 
     @patch('patroni.postgresql.CallbackExecutor', Mock())
@@ -99,6 +101,48 @@ class TestBootstrap(BaseTestPostgresql):
         self.assertRaises(Exception, self.b.bootstrap, {'initdb': [1]})
         self.assertRaises(Exception, self.b.bootstrap, {'initdb': 1})
 
+    def test__process_user_options(self):
+        def error_handler(msg):
+            raise Exception(msg)
+
+        self.assertEqual(self.b.process_user_options('initdb', ['string'], (), error_handler), ['--string'])
+        self.assertEqual(
+            self.b.process_user_options(
+                'initdb',
+                [{'key': 'value'}],
+                (), error_handler
+            ),
+            ['--key=value'])
+        if sys.platform != 'win32':
+            self.assertEqual(
+                self.b.process_user_options(
+                    'initdb',
+                    [{'key': 'value with spaces'}],
+                    (), error_handler
+                ),
+                ["--key=value with spaces"])
+            self.assertEqual(
+                self.b.process_user_options(
+                    'initdb',
+                    [{'key': "'value with spaces'"}],
+                    (), error_handler
+                ),
+                ["--key=value with spaces"])
+            self.assertEqual(
+                self.b.process_user_options(
+                    'initdb',
+                    {'key': 'value with spaces'},
+                    (), error_handler
+                ),
+                ["--key=value with spaces"])
+            self.assertEqual(
+                self.b.process_user_options(
+                    'initdb',
+                    {'key': "'value with spaces'"},
+                    (), error_handler
+                ),
+                ["--key=value with spaces"])
+
     @patch.object(CancellableSubprocess, 'call', Mock())
     @patch.object(Postgresql, 'is_running', Mock(return_value=True))
     @patch.object(Postgresql, 'data_directory_empty', Mock(return_value=False))
@@ -111,9 +155,9 @@ class TestBootstrap(BaseTestPostgresql):
 
         config = {'users': {'replicator': {'password': 'rep-pass', 'options': ['replication']}}}
 
-        with patch.object(Postgresql, 'is_running', Mock(return_value=False)),\
-                patch.object(Postgresql, 'get_major_version', Mock(return_value=140000)),\
-                patch('multiprocessing.Process', Mock(side_effect=Exception)),\
+        with patch.object(Postgresql, 'is_running', Mock(return_value=False)), \
+                patch.object(Postgresql, 'get_major_version', Mock(return_value=140000)), \
+                patch('multiprocessing.Process', Mock(side_effect=Exception)), \
                 patch('multiprocessing.get_context', Mock(side_effect=Exception), create=True):
             self.assertRaises(Exception, self.b.bootstrap, config)
         with open(os.path.join(self.p.data_dir, 'pg_hba.conf')) as f:
@@ -132,7 +176,7 @@ class TestBootstrap(BaseTestPostgresql):
 
     @patch.object(CancellableSubprocess, 'call')
     @patch.object(Postgresql, 'get_major_version', Mock(return_value=90600))
-    @patch.object(Postgresql, 'controldata',  Mock(return_value={'Database cluster state': 'in production'}))
+    @patch.object(Postgresql, 'controldata', Mock(return_value={'Database cluster state': 'in production'}))
     def test_custom_bootstrap(self, mock_cancellable_subprocess_call):
         self.p.config._config.pop('pg_hba')
         config = {'method': 'foo', 'foo': {'command': 'bar'}}
@@ -141,12 +185,12 @@ class TestBootstrap(BaseTestPostgresql):
         self.assertFalse(self.b.bootstrap(config))
 
         mock_cancellable_subprocess_call.return_value = 0
-        with patch('multiprocessing.Process', Mock(side_effect=Exception("42"))),\
-                patch('multiprocessing.get_context', Mock(side_effect=Exception("42")), create=True),\
-                patch('os.path.isfile', Mock(return_value=True)),\
-                patch('os.unlink', Mock()),\
-                patch.object(ConfigHandler, 'save_configuration_files', Mock()),\
-                patch.object(ConfigHandler, 'restore_configuration_files', Mock()),\
+        with patch('multiprocessing.Process', Mock(side_effect=Exception("42"))), \
+                patch('multiprocessing.get_context', Mock(side_effect=Exception("42")), create=True), \
+                patch('os.path.isfile', Mock(return_value=True)), \
+                patch('os.unlink', Mock()), \
+                patch.object(ConfigHandler, 'save_configuration_files', Mock()), \
+                patch.object(ConfigHandler, 'restore_configuration_files', Mock()), \
                 patch.object(ConfigHandler, 'write_recovery_conf', Mock()):
             with self.assertRaises(Exception) as e:
                 self.b.bootstrap(config)
@@ -194,7 +238,8 @@ class TestBootstrap(BaseTestPostgresql):
         self.p.reload_config({'authentication': {'superuser': {'username': 'p', 'password': 'p'},
                                                  'replication': {'username': 'r', 'password': 'r'},
                                                  'rewind': {'username': 'rw', 'password': 'rw'}},
-                              'listen': '*', 'retry_timeout': 10, 'parameters': {'wal_level': '', 'hba_file': 'foo'}})
+                              'listen': '*', 'retry_timeout': 10,
+                              'parameters': {'wal_level': '', 'hba_file': 'foo', 'max_prepared_transactions': 10}})
         with patch.object(Postgresql, 'major_version', PropertyMock(return_value=110000)), \
                 patch.object(Postgresql, 'restart', Mock()) as mock_restart:
             self.b.post_bootstrap({}, task)