Re: Synchronizing slots from primary to standby

Hi,

On Fri, Apr 05, 2024 at 09:43:35AM +0530, shveta malik wrote:
> On Fri, Apr 5, 2024 at 9:22 AM Bertrand Drouvot
> <bertranddrouvot(dot)pg(at)gmail(dot)com> wrote:
> >
> > Hi,
> >
> > On Thu, Apr 04, 2024 at 05:31:45PM +0530, shveta malik wrote:
> > > On Thu, Apr 4, 2024 at 2:59 PM shveta malik <shveta(dot)malik(at)gmail(dot)com> wrote:
> > 2 ===
> >
> > + if (slot->data.confirmed_flush != remote_slot->confirmed_lsn)
> > + elog(LOG,
> > + "could not synchronize local slot \"%s\" LSN(%X/%X)"
> > + " to remote slot's LSN(%X/%X) ",
> > + remote_slot->name,
> > + LSN_FORMAT_ARGS(slot->data.confirmed_flush),
> > + LSN_FORMAT_ARGS(remote_slot->confirmed_lsn));
> >
> > I don't think that the message is correct here. Unless I am missing something
> > there is nothing in the following code path that would prevent the slot to be
> > sync during this cycle.
>
> This is a sanity check, I will put a comment to indicate the same.

Thanks!

> We
> want to ensure if anything changes in future, we get correct logs to
> indicate that.

Right, understood that way.

> If required, the LOG msg can be changed. Kindly suggest if you have
> anything better in mind.
>

What about something like?

ereport(LOG,
errmsg("synchronized confirmed_flush_lsn for slot \"%s\" differs from remote slot",
remote_slot->name),
errdetail("Remote slot has LSN %X/%X but local slot has LSN %X/%X.",
LSN_FORMAT_ARGS(remote_slot->restart_lsn),
LSN_FORMAT_ARGS(slot->data.restart_lsn));

Regards,

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