Re: Synchronizing slots from primary to standby

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.

> 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?

--
With Regards,
Amit Kapila.