Re: Synchronizing slots from primary to standby

On Wed, Jan 24, 2024 at 2:43 PM Amit Kapila <amit(dot)kapila16(at)gmail(dot)com> wrote:
>
> On Wed, Jan 24, 2024 at 10:41 AM Masahiko Sawada <sawada(dot)mshk(at)gmail(dot)com> wrote:
> >
> > On Mon, Jan 22, 2024 at 3:58 PM Amit Kapila <amit(dot)kapila16(at)gmail(dot)com> wrote:
> > >
> > > Can we think of using GetStandbyFlushRecPtr()? We probably need to
> > > expose this function, if this works for the required purpose.
> >
> > GetStandbyFlushRecPtr() seems good. But do we really want to raise an
> > ERROR in this case? IIUC this case could happen often when the slot
> > used by the standby is not listed in standby_slot_names.
> >
>
> or it can be due to some bug in the code as well.
>
> > I think we
> > can just skip such a slot to synchronize and check it the next time.
> >
>
> How about logging the message and then skipping the sync step? This
> will at least make users aware that they could be missing to set
> standby_slot_names.

+1

>
> > Here are random comments on slotsyncworker.c (v66):
> >
> > +/* GUC variable */
> > +bool enable_syncslot = false;
> >
> > Is enable_syncslot a really good name? We use "enable" prefix only for
> > planner parameters such as enable_seqscan, and it seems to me that
> > "slot" is not specific. Other candidates are:
> >
> > * synchronize_replication_slots = on|off
> > * synchronize_failover_slots = on|off
> >
>
> I would prefer the second one. Would it be better to just say
> sync_failover_slots?

Works for me. But if we want to extend this option for non-failover
slots as well in the future, synchronize_replication_slots (or
sync_replication_slots) seems better. We can extend it by having an
enum later. For example, the values can be on, off, or failover etc.

Regards,

--
Masahiko Sawada
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