It is very easy to get current timeline on the master by executing
```sql
SELECT ('x' || SUBSTR(pg_walfile_name(pg_current_wal_lsn()), 1, 8))::bit(32)::int
```
Unfortunately the same method doesn't work when postgres is_in_recovery. Therefore we will use replication connection for that on the replicas. In order to avoid opening and closing replication connection on every HA loop we will cache the result if its value matches with the timeline of the master.
Also this PR introduces a new key in DCS: `/history`. It will contain a json serialized object with timeline history in a format similar to the usual history files. The differences are:
* Second column is the absolute wal position in bytes, instead of LSN
* Optionally there might be a fourth column - timestamp, (mtime of history file)
Every iteration of HA loop Patroni needs to call pg_is_in_recovery() and calcualte absolute wal_position. It was doing two separate SELECT statements for that. In case of master it was doing even three queries (wal_position two times).
We will issue one SELECT for every HA loop and cache the results.
* Use scope from config file when listing members
* Add version command to patronictl
* Only delete leader on shutdown when we have the lock to avoid exceptions when leader key does not exist
* Add a timestamp option to list command.
* YAML format for patronictl output
* Fix API request to get version
Make it possible to cancel a running task if you want to reinitialize replica.
There are two possible ways to trigger it:
1. patronictl will ask whether you want to cancel already running task if an attempt to trigger reinitialize has failed
2. if you are using `--force` argument with `patronictl reinit`
This list will be used for initial discovery of etcd cluster members.
If for some reason during work this list of hosts has been exhausted (during work), Patroni will return to initial list.
In addition to that improve ipv6 compatibility by using a special function for splitting host and port.
Fixes https://github.com/zalando/patroni/issues/523
* Use ConfigMaps or Endpoins for leader elections and to keep cluster state
* Label pods with a postgres role
* change behavior of pip install. From now on it will not install all dependencies, you have to specify explicitly DCS you want to use Patroni with: `pip install patroni[etcd,zookeeper,kubernetes]`
* Show information about scheduled failover and maintenance mode when showing list of cluster members. Fixes https://github.com/zalando/patroni/issues/557
* Fix postgres version check functions (postgres 10 and above compatibility) and apply pep8 formatting to the tests.
* Bump some configuration parameters to match with postgres 10 defaults.
* Fix name of contributor in release notes.
Introduces a PostmasterProcess object that identifies a running process via pid and start time.
When pid file is parsed and the correct process identified this object is passed around.
When the process goes away we try to find a new one in case somebody restarted postgres behind our back.
After a crash that doesn't clean up postmaster.pid there could be a new process with the same pid resulting in a false positive for is_running(), which will lead to all kinds of bad behavior.
Fixes#548
It could happen that ttl provided in Patroni configuration is smaller
than minimum supported by Consul. In such case Consul agent fails to
create a new session and responds with 500 Internal Server Error and
http body contains something like: "Invalid Session TTL '3000000000',
must be between [10s=24h0m0s]". Without session Patroni is not able to
create member and leader keys in the Consul KV store and it means that
cluster becomes completely unhealthy.
As a workaround we will handle such exception, adjust ttl to the minimum
possible and retry session creation.
In addition to that make it possible to define custom log format via environment variable `PATRONI_LOGFORMAT`
If list of checks is not specified, Consul will use "serfHealth" in addition to TTL based created by Patroni.
There are some cases when people want to sacrifice fast detection of network partitioning in favor of ability to tolerate network lags.
Fixes https://github.com/zalando/patroni/issues/522
When Patroni does calculation whether it should run pg_rewind or not, it relies on pg_controldata output or gets necessary information from replication connection.
On some cases (when for example postgres running as a master was killed), we can't use pg_controldata output immediately, but trying to start postgres. Such start could fail with the following errror:
```
LOG,00000,"ending log output to stderr",,"Future log output will go to log destination ""csvlog"".",,,,,,,""
LOG,00000,"database system was interrupted; last known up at 2017-09-16 22:35:22 UTC",,,,,,,,,""
LOG,00000,"restored log file ""00000006.history"" from archive",,,,,,,,,""
LOG,00000,"entering standby mode",,,,,,,,,"" 2017-09-18 08:00:39.433 UTC,,,57,,59bf7d26.39,4,,2017-09-18 08:00:38 UTC,,0,LOG,00000,"restored log file ""00000006.history"" from archive",,,,,,,,,""
FATAL,XX000,"requested timeline 6 is not a child of this server's history","Latest checkpoint is at 29/1A000178 on timeline 5, but in the history of the requested timeline, the server forked off from that timeline at 29/1A000140.",,,,,,,,""
LOG,00000,"startup process (PID 57) exited with exit code 1",,,,,,,,,""
LOG,00000,"aborting startup due to startup process failure",,,,,,,,,""
LOG,00000,"database system is shut down",,,,,,,,,""
```
In this case controldata will still have `Database cluster state: in production`
All further attempts to start postgres will fail. Such situation could be fixed only if we start not in recovery. For safety we will do it in a single user mode.
The second problems is: if postgres was running as master, but later we started it and stopped, than pg_controldata will report:
```
Database cluster state: shut down in recovery
Minimum recovery ending location: 0/0
Min recovery ending loc's timeline: 0
```
And this info can't be used for calculations. In this case we should use
`Latest checkpoint location` and `Latest checkpoint's TimeLineID`
A misunderstanding of the ioctl() call interface. If mutable=False then fcntl.ioctl() actually returns the arg buffer back.
This accidentally worked on Python2 because int and str comparison did not return an error.
Error reporting is actually done by raising IOError on Python2 and OSError on Python3.
* Properly handle errors in set_timeout(), have them result in only a warning if watchdog support is not required.
* Improve watchdog device driver name display on Python3
* Eliminate race condition in watchdog feature tests.
The pinged/closed states were not getting reset properly if the checks ran too quickly.
Add explicit reset points in feature test so the check is unambiguous.
in addition to that implement additional checks around manual failover and recover when synchronous_mode is enabled
* Comparison must be case insensitive
* Do not send keepalives if watchdog is not active
* Avoid activating watchdog in a pause mode
* Set correct postgres state in pause mode
* Don't try to run queries from API if postgres is stopped
* Short after promote synchronous replication was disabled even is synchronous_mode_strict is set
* Create empty pg_ident.conf if it is missing after restoring from backup
* Bump version
When updating config key we should use `ClusterConfig.index` instead of
`ClusterConfig.modify_index`. The second one should be used by Patroni
internally to check that key was really changed, because when key is
deleted and recreated it's version always starts from the same value: 0
In addition to that use patronictl instead of http PATCH in some of
acceptance tests to change cluster config.
Fixes https://github.com/zalando/patroni/issues/491
Originally fetch_nodes_statuses was returning a tuple, later it was
wrapped into namedtuple _MemberStatus and recently _MemberStatus was
extened with watchdog_failed field, but api.py was still relying on
usual tuple and checking failover limitations on it's own instead of
calling `failover_limitation` method.
* Only activate watchdog while master and not paused
We don't really need the protections while we are not master. This way
we only need to tickle the watchdog when we are updating leader key or
while demotion is happening.
As implemented we might fail to notice to shut down the watchdog if
someone demotes postgres and removes leader key behind Patroni's back.
There are probably other similar cases. Basically if the administrator
if being actively stupid they might get unexpected restarts. That seems
fine.
* Add configuration change support. Change MODE_REQUIRED to disable leader eligibility instead of closing Patroni.
Changes watchdog timeout during the next keepalive when ttl is changed. Watchdog driver and requirement can also be switched online.
When watchdog mode is `required` and watchdog setup does not work then the effect is similar to nofailover. Add watchdog_failed to status API to signify this. This is True only when watchdog does not work **AND** it is required.
* Reset implementation when config changed while active.
* Add watchdog safety margin configuration
Defaults to 5 seconds. Basically this is the maximum amount of time
that can pass between the calls to odcs.update_leader()` and
`watchdog.keepalive()`, which are called right after each other. Should
be safe for pretty much any sane scenario and allows the default
settings to not trigger watchdog when DCS is not responding.
* Cancel bootstrap if watchdog activation fails
The system would have demoted itself anyway the next HA loop. Doing it
in bootstrap gives at least some other node chance to try bootstrapping
in the hope that it is configured correctly.
If all nodes are unable to activate they will continue to try until the
disk is filled with moved datadirs. Perhaps not ideal behavior, but as
the situation is unlikely to resolve itself without administrator
intervention it doesn't seem too bad.
It wasn't a big issue when on_start was called during normal boostrap
with initdb, because usually such process is very fast. But situation is
changing when we run custom bootstrap, becuase it might be a long time
between cluster become connectable and end of recovery and promote.
Actually situation was even worse than that, on_start was called with
the `replica` argument and later on_role_changes was never called,
because promote wasn't performed by Patroni.
As a solution for this problem we will block any callbacks during
bootstrap and explicitly call on_start after leader lock was taken.
