Re: hot_standby_feedback parameter doesn't work

On Tue, Nov 13, 2018 at 2:34 PM Rui DeSousa <rui(at)crazybean(dot)net> wrote:
>
>
>
> > On Nov 12, 2018, at 10:28 PM, Andrey Zhidenkov <andrey(dot)zhidenkov(at)gmail(dot)com> wrote:
> >
> > We have a few database clusters (1 master, 2 hot standbys) with
> > hot_standby_feedback setting on. But I am constantly seeing query
> > conflicts on standbys because dead rows on the masters are deleted by
> > VACUUM. Usually I notice it shortly after VACUUM ends, because the
> > replication lag on replicas is starting to increase.
> >
> > vacuum_defer_cleanup_age = 0. PostgreSQL version is 9.5.13. Cluster
> > load is about 1500 transactions per second.
> >
> > Any ideas?
> >
> > -
> > With the best regards, Andrey Zhidenkov
> >
>
> Are these streaming replicas? The wal_streaming process on the master should show the xmin of the replicas; you can check the value from pg_stat_activity to make sure the feedback is occurring.
>
Yes, they are streaming replicas. Could you please tell me how to
check xmin of the replica in pg_stat_activity? I didn't get the point.

> Are the replicas disconnecting from the replication stream? As the would mean the xmin from the replica would no longer be in play.

No, the replicas are not disconnecting.

--
-
With best regards, Andrey Zhidenkov