Check Replication lag

On Mon, Oct 11, 2021 at 05:58:03PM +0530, Pawan Sharma wrote:

Is there a way to monitor the replication lag, where replica nodes are
configured through aws s3.

You can check it on replica, by issuing:
select now() - pg_last_xact_replay_timestamp();

and it will show you, more or less, what is your current lag.

Best regards,

depesz

Hello Depesz,

Thanks for your quick response, let me give some overview of our cluster
setups. Actually we have a Patroni cluster running with one replica
(Replica 1) in the same data center with no data lag. whereas we have
configured one more replica(Replica 2) in a different data center
through AWS S3 WAL shipping and replaying.

So we can easily check Patroni replica (Replica1) lag using the patronictl
list command. but I am looking how I can check replication lag of Replica 2
which is configured through AWS.

As I have checked with above query I am getting same response from both the
replicas. whereas on Replica2 there is some lag exist.

I have created dummy table on master node and its synced on replica1
simultaneously but it taking hours to sync on replica2.

Regards,
Pawan

On Mon, Oct 11, 2021 at 6:22 PM hubert depesz lubaczewski <depesz@depesz.com>
wrote: