Alexander Kukushkin 96b75fa7cb Special handling of check_recovery_conf for v12+ (#2292) ...

When starting as a replica it may take some time before Postgres starts accepting new connections, but meanwhile, it could happen that the leader transitioned to a different member and the `primary_conninfo` must be updated.

On pre v12 Patroni regularly checks `recovery.conf` in order to check that recovery parameters match the expectation. Starting from v12 recovery parameters were converted to GUC's and Patroni gets current values from the `pg_settings` view. The last one creates a problem when it takes more than a minute for Postgres to start accepting new connections.

Since Patroni attempts to execute at least `pg_is_in_recovery()` every HA loop, and it is raising at exception, the `check_recovery_conf()` effectively wasn't reachable until recovery is finished, but it changed when #2082 was introduced.

As a result of #2082 we got the following behavior:
1. Up to v12 (not including) everything was working as expected
2. v12 and v13 - Patroni restarting Postgres after 1m of recovery
3. v14+ - the `check_recovery_conf()` is not executed because the `replay_paused()` method raising an exception.

In order to properly handle changes of recovery parameters or leader transitioned to a different node on v12+, we will rely on the cached values of recovery parameters until Postgres becomes ready to execute queries.

Close https://github.com/zalando/patroni/issues/2289

2022-05-12 07:45:49 +02:00

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