Re: Temporary disabling a replica in a Patroni cluster

Hello Victor,


Am 25.08.2023 um 13:18 schrieb Victor Sudakov:
> Dear Colleagues,
>
> Do you perchance know what is the correct procedure of temporarily
> taking down a replica in a Patroni cluster, e.g. for 5-10 minutes of
> hardware maintenance?
>
> The problem is that after stopping the patroni process (service) on a
> replica, patroni removes the corresponding physical replication slot
> from the leader, and unless the wal_keep_size value is unsanely high,
> the replica, when up again, cannot restart streaming because the WAL
> segments are already gone from the leader.
>
> Well, you all know:
> <%%%>LOG:  started streaming WAL from primary at B4A0/E2000000 on timeline 8
> <%%%>FATAL:  could not receive data from WAL stream: ERROR:  requested WAL segment 000000080000B4A0000000E2 has
alreadybeen removed
 
> <%%%>LOG:  waiting for WAL to become available at B4A0/E2002000
>
> Do you think there is a way to tell Patroni that a replica is down
> temporarily and its replication slot should not be removed?
>
> Or, what am I missing?


you may use patronictl pause + resume

keep in mind to set wal_keep_size (or wal_keep_segments depending on 
your PG version high enough)

regards

Georg