RE: Reload configuration more frequently in apply worker.

On Wednesday, May 17, 2023 11:05 AM Amit Kapila <amit(dot)kapila16(at)gmail(dot)com> wrote:
>
> On Wed, May 17, 2023 at 7:18 AM Zhijie Hou (Fujitsu) <houzj(dot)fnst(at)fujitsu(dot)com>
> wrote:
> >
> > Currently, the main loop of apply worker looks like below[1]. Since
> > there are two loops, the inner loop will keep receiving and applying
> > message from publisher until no more message left. The worker only
> > reloads the configuration in the outer loop. This means if the
> > publisher keeps sending messages (it could keep sending multiple
> > transactions), the apply worker won't get a chance to update the GUCs.
> >
>
> Apart from that, I think in rare cases, it seems possible that after the apply
> worker has waited for the data and just before it receives the new replication
> data/message, the reload happens, then it won't get a chance to process the
> reload before processing the new message.
> I think such a theory can explain the rare BF failure you pointed out later in the
> thread. Does that make sense?

Yes, that makes sense. That's another case where we would miss the reload and I think
is the reason for the failure because the apply worker has finished applying changes(which
means it's idle) before the failed case.

Best Regards,
Hou zj