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Ants AasmaandOleksii Kliukin
7e53a604d4
Adds a new configuration variable synchronous_mode. When enabled Patroni will manage synchronous_standby_names to enable synchronous replication whenever there are healthy standbys available. With synchronous mode enabled Patroni will automatically fail over only to a standby that was synchronously replicating at the time of master failure. This effectively means zero lost user visible transactions. To enforce the synchronous failover guarantee Patroni stores current synchronous replication state in the DCS, using strict ordering, first enable synchronous replication, then publish the information. Standby can use this to verify that it was indeed a synchronous standby before master failed and is allowed to fail over. We can't enable multiple standbys as synchronous, allowing PostreSQL to pick one because we can't know which one was actually set to be synchronous on the master when it failed. This means that on standby failure commits will be blocked on the master until next run_cycle iteration. TODO: figure out a way to poke Patroni to run sooner or allow for PostgreSQL to pick one without the possibility of lost transactions. On graceful shutdown standbys will disable themselves by setting a nosync tag for themselves and waiting for the master to notice and pick another standby. This adds a new mechanism for Ha to publish dynamic tags to the DCS. When the synchronous standby goes away or disconnects a new one is picked and Patroni switches master over to the new one. If no synchronous standby exists Patroni disables synchronous replication (synchronous_standby_names=''), but not synchronous_mode. In this case, only the node that was previously master is allowed to acquire the leader lock. Added acceptance tests and documentation. Implementation by @ants with extensive review by @CyberDem0n.
96 lines
8.4 KiB
ReStructuredText
96 lines
8.4 KiB
ReStructuredText
===========================
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YAML Configuration Settings
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===========================
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Global/Universal
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----------------
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- **name**: the name of the host. Must be unique for the cluster.
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- **namespace**: path within the configuration store where Patroni will keep information about the cluster. Default value: "/service"
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- **scope**: cluster name
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Bootstrap configuration
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-----------------------
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- **dcs**: This section will be written into `/<namespace>/<scope>/config` of a given configuration store after initializing of new cluster. This is the global configuration for the cluster. If you want to change some parameters for all cluster nodes - just do it in DCS (or via Patroni API) and all nodes will apply this configuration.
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- **loop\_wait**: the number of seconds the loop will sleep. Default value: 10
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- **ttl**: the TTL to acquire the leader lock. Think of it as the length of time before initiation of the automatic failover process. Default value: 30
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- **maximum\_lag\_on\_failover**: the maximum bytes a follower may lag to be able to participate in leader election.
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- **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 succesfully committed transactions will not be lost at failover, at the cost of losing availability for writes when Patroni cannot ensure transaction durability. See `replication modes documentation <https://github.com/zalando/patroni/blob/master/docs/replication_modes.rst>`__ for details.
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- **postgresql**:
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- **use\_pg\_rewind**:whether or not to use pg_rewind
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- **use\_slots**: whether or not to use replication_slots. Must be False for PostgreSQL 9.3. You should comment out max_replication_slots before it becomes ineligible for leader status.
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- **recovery\_conf**: additional configuration settings written to recovery.conf when configuring follower.
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- **parameters**: list of configuration settings for Postgres. Many of these are required for replication to work.
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- **initdb**: List options to be passed on to initdb.
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- **- data-checksums**: Must be enabled when pg_rewind is needed on 9.3.
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- **- encoding: UTF8**: default encoding for new databases.
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- **- locale: UTF8**: default locale for new databases.
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- **pg\_hba**: list of lines that you should add to pg\_hba.conf.
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- **- host all all 0.0.0.0/0 md5**.
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- **- host replication replicator 127.0.0.1/32 md5**: A line like this is required for replication.
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- **users**: Some additional users users which needs to be created after initializing new cluster
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- **admin**: the name of user
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- **password: zalando**:
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- **options**: list of options for CREATE USER statement
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- **- createrole**
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- **- createdb**
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- **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.
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Consul
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------
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- **host**: the host:port for the Consul endpoint.
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Etcd
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----
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- **host**: the host:port for the etcd endpoint.
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Exhibitor
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---------
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- **hosts**: initial list of Exhibitor (ZooKeeper) nodes in format: 'host1,host2,etc...'. This list updates automatically whenever the Exhibitor (ZooKeeper) cluster topology changes.
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- **poll\_interval**: how often the list of ZooKeeper and Exhibitor nodes should be updated from Exhibitor
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- **port**: Exhibitor port.
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PostgreSQL
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----------
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- **authentication**:
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- **superuser**:
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- **username**: name for the superuser, set during initialization (initdb) and later used by Patroni to connect to the postgres.
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- **password**: password for the superuser, set during initialization (initdb).
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- **replication**:
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- **username**: replication username; the user will be created during initialization. Replicas will use this user to access master via streaming replication
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- **password**: replication password; the user will be created during initialization.
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- **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.)
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- **on\_reload**: run this script when configuration reload is triggered.
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- **on\_restart**: run this script when the cluster restarts.
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- **on\_role\_change**: run this script when the cluster is being promoted or demoted.
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- **on\_start**: run this script when the cluster starts.
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- **on\_stop**: run this script when the cluster stops.
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- **connect\_address**: IP address + port through which Postgres is accessible from other nodes and applications.
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- **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.
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- **data\_dir**: The location of the Postgres data directory, either existing or to be initialized by Patroni.
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- **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.
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- **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.
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- **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.
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- **recovery\_conf**: additional configuration settings written to recovery.conf when configuring follower.
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- **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 overriden by Patroni's own configuration facilities - see `dynamic configuration <https://github.com/zalando/patroni/blob/master/docs/dynamic_configuration.rst>`__ for details.
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- **parameters**: list of configuration settings for Postgres. Many of these are required for replication to work.
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- **pg\_ctl\_timeout**: How long should pg_ctl wait when doing ``start``, ``stop`` or ``restart``. Default value is 60 seconds.
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- **use\_pg\_rewind**: try to use pg\_rewind on the former leader when it joins cluster as a replica.
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- **remove\_data\_directory\_on\_rewind\_failure**: If this option is enabled, Patroni will remove postgres data directory and recreate replica. Otherwise it will try to follow the new leader. Default value is **false**.
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- **replica\_method** for each create_replica_method 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".
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REST API
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--------
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- **connect\_address**: IP address and port to access the REST API.
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- **listen**: IP address and port that Patroni will listen to, to provide health-check information for HAProxy.
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- **Optional**:
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- **authentication**:
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- **username**: Basic-auth username to protect unsafe REST API endpoints.
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- **password**: Basic-auth password to protect unsafe REST API endpoints.
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- **certfile**: 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.
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- **keyfile**: Specifies the file with the secret key in the PEM format.
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ZooKeeper
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----------
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- **hosts**: list of ZooKeeper cluster members in format: ['host1:port1', 'host2:port2', 'etc...'].
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