Re: Synchronizing slots from primary to standby

Hi,

On Tue, Apr 02, 2024 at 02:19:30PM +0530, Amit Kapila wrote:
> On Tue, Apr 2, 2024 at 1:54 PM Bertrand Drouvot
> <bertranddrouvot(dot)pg(at)gmail(dot)com> wrote:
> > What about adding a "wait" injection point in LogStandbySnapshot() to prevent
> > checkpointer/bgwriter to log a standby snapshot? Something among those lines:
> >
> > if (AmCheckpointerProcess() || AmBackgroundWriterProcess())
> > INJECTION_POINT("bgw-log-standby-snapshot");
> >
> > And make use of it in the test, something like:
> >
> > $node_primary->safe_psql('postgres',
> > "SELECT injection_points_attach('bgw-log-standby-snapshot', 'wait');");
> >
>
> Sometimes we want the checkpoint to log the standby snapshot as we
> need it at a predictable time, maybe one can use
> pg_log_standby_snapshot() instead of that. Can we add an injection
> point as a separate patch/commit after a bit more discussion?

Sure, let's come back to this injection point discussion after the feature
freeze. BTW, I think it could also be useful to make use of injection point for
the test that has been added in 7f13ac8123.

I'll open a new thread for this at that time.

>. One other
> idea to make such tests predictable is to add a developer-specific GUC
> say debug_bg_log_standby_snapshot or something like that but injection
> point sounds like a better idea.

Agree.

Regards,

--
Bertrand Drouvot
PostgreSQL Contributors Team
RDS Open Source Databases
Amazon Web Services: https://aws.amazon.com