Re: Failure of subscription tests with topminnow

On Wed, Aug 25, 2021 at 5:54 PM Ajin Cherian <itsajin(at)gmail(dot)com> wrote:
>
> On Wed, Aug 25, 2021 at 9:32 PM Masahiko Sawada <sawada(dot)mshk(at)gmail(dot)com> wrote:
>
> >
> > IIUC the query[1] used for polling returns two rows in this case: {t,
> > f} or {f, t}. But did poll_query_until() returned OK in this case even
> > if we expected one row of 't'? My guess of how this issue happened is:
> >
> > 1. the first polling query after "ATLER SUBSCRIPTION CONNECTION"
> > passed (for some reason).
> > 2. all wal senders exited.
> > 3. get the pid of wal sender with application_name 'tap_sub' but got nothing.
> > 4. the second polling query resulted in a syntax error since $oldpid is null.
> >
> > If the fact that two walsender with the same application_name could
> > present in pg_stat_replication view was the cause of this issue,
> > poll_query_until() should return OK even if we expected just 't'. I
> > might be missing something, though.
> >
> > [1] "SELECT pid != $oldpid FROM pg_stat_replication WHERE
> > application_name = '$appname';"
>
> Yes, the query [1] returns OK with a {f,t} or {t,f}
>
> [1] - "SELECT pid != $oldpid FROM pg_stat_replication WHERE
> application_name = '$appname';"
>

Can you additionally check the value of 'state' from
pg_stat_replication for both the old and new walsender sessions?

--
With Regards,
Amit Kapila.