RE: Synchronizing slots from primary to standby

On Monday, February 5, 2024 10:17 AM Zhijie Hou (Fujitsu) <houzj(dot)fnst(at)fujitsu(dot)com> wrote:
>
> On Friday, February 2, 2024 2:56 PM Amit Kapila <amit(dot)kapila16(at)gmail(dot)com>
> wrote:
> >
> > 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.
>
> Here is an attempt for this. The slotsync worker patch is now splitted into two
> patches(0002 and 0003). I also adjusted the doc, comments and tests for the
> new pg_synchronize_slots() function.

There was one miss in the doc that cause CFbot failure,
attach the correct version V77_2 here. There are no code changes compared to V77 version.

Best Regards,
Hou zj