Check replication settings:
max_standby_archive_delay
max_standby_streaming_delay
hot_standby_feedback
These can delay wals being applied to the replica while queries are
still running.
Regards,
Michael Vitale
Nikhil Shetty wrote on 11/24/2020 9:24 AM:
> Hi,
>
> We have one Primary and three Standby Postgresql setup. Two standby in
> DC and one standby in DR.
>
> We have configured streaming replication.When there are a lot of write
> transactions in the master, we observed that DR lags behind the master
> for 5-6 hours. We initially thought this could be because of the slow
> network between DC and DR and this is normal but when we saw the
> replay_lsn and receive_lsn , they had a huge difference.
>
> DR standby was receiving the WAL's in time and there was no delay, the
> delay was in replaying the lag. Can anybody point me to where I can
> start with the investigation?
> DC (Master and 2 Standby) and DR(Standby) have the same setup in terms
> of storage and some database configuration parameters but DR has a
> little less CPU and RAM.
>
> Attaching replay and receive wal difference.
>