Re: Synchronizing slots from primary to standby

On Thu, Feb 1, 2024 at 5:29 PM shveta malik <shveta(dot)malik(at)gmail(dot)com> wrote:
>
> On Thu, Feb 1, 2024 at 2:35 PM Amit Kapila <amit(dot)kapila16(at)gmail(dot)com> wrote:
> >
> > Agreed, and I am fine with merging 0001, 0002, and 0004 as suggested
> > by you though I have a few minor comments on 0002 and 0004. I was
> > thinking about what will be a logical way to split the slot sync
> > worker patch (combined result of 0001, 0002, and 0004), and one idea
> > occurred to me is that we can have the first patch as
> > synchronize_solts() API and the functionality required to implement
> > that API then the second patch would be a slot sync worker which uses
> > that API to synchronize slots and does all the required validations.
> > Any thoughts?
>
> If we shift 'synchronize_slots()' to the first patch but there is no
> caller of it, we may have a compiler warning for the same. The only
> way it can be done is if we temporarily add SQL function on standby
> which uses 'synchronize_slots()'. This SQL function can then be
> removed in later patches where we actually have a caller for
> 'synchronize_slots'.
>

Can such a SQL function say pg_synchronize_slots() which can sync all
slots that have a failover flag set be useful in general apart from
just writing tests for this new API? I am thinking maybe users want
more control over when to sync the slots and write their bgworker or
simply do it just before shutdown once (sort of planned switchover) or
at some other pre-defined times. BTW, we also have
pg_log_standby_snapshot() which otherwise would be done periodically
by background processes.

>
> 1) Re-arranged the patches:
> 1.1) 'libpqrc' related changes (from v74-001 and v74-004) are
> separated out in v75-001 as those are independent changes.

Bertrand, Sawada-San, and others, do you see a problem with such a
split? Can we go ahead with v75_0001 separately after fixing the open
comments?

--
With Regards,
Amit Kapila.