Re: Synchronizing slots from primary to standby

On Fri, Sep 22, 2023 at 3:48 PM Amit Kapila <amit(dot)kapila16(at)gmail(dot)com> wrote:
>
> On Thu, Sep 21, 2023 at 9:16 AM shveta malik <shveta(dot)malik(at)gmail(dot)com> wrote:
> >
> > On Tue, Sep 19, 2023 at 10:29 AM shveta malik <shveta(dot)malik(at)gmail(dot)com> wrote:
> >
> > Currently in patch001, synchronize_slot_names is a GUC on both primary
> > and physical standby. This GUC tells which all logical slots need to
> > be synced on physical standbys from the primary. Ideally it should be
> > a GUC on physical standby alone and each physical standby should be
> > able to communicate the value to the primary (considering the value
> > may vary for different physical replicas of the same primary). The
> > primary on the other hand should be able to take UNION of these values
> > and let the logical walsenders (belonging to the slots in UNION
> > synchronize_slots_names) wait for physical standbys for confirmation
> > before sending those changes to logical subscribers. The intent is
> > logical subscribers should never be ahead of physical standbys.
> >
>
> Before getting into the details of 'synchronize_slot_names', I would
> like to know whether we really need the second GUC
> 'standby_slot_names'. Can't we simply allow all the logical wal
> senders corresponding to 'synchronize_slot_names' to wait for just the
> physical standby(s) (physical slot corresponding to such physical
> standby) that have sent ' synchronize_slot_names'list? We should have
> one physical standby slot corresponding to one physical standby.
>

yes, with the new approach (to be implemented next) where we plan to
send synchronize_slot_names from each physical standby to primary, the
standby_slot_names GUC should no longer be needed on primary. The
physical standbys sending requests should automatically become the
ones to be waited for confirmation on the primary.

thanks
Shveta