Re: Improve pg_sync_replication_slots() to wait for primary to advance

On Tue, Aug 5, 2025 at 4:22 PM Amit Kapila <amit(dot)kapila16(at)gmail(dot)com> wrote:
>
> On Tue, Aug 5, 2025 at 9:28 AM shveta malik <shveta(dot)malik(at)gmail(dot)com> wrote:
> >
> > On Mon, Aug 4, 2025 at 3:41 PM Amit Kapila <amit(dot)kapila16(at)gmail(dot)com> wrote:
> > >
> > > On Mon, Aug 4, 2025 at 12:19 PM shveta malik <shveta(dot)malik(at)gmail(dot)com> wrote:
> >
> > If we want to avoid continuously syncing newly added slots in later
> > cycles and instead focus only on the ones that failed to sync during
> > the first attempt, one approach is to maintain a list of failed slots
> > from the initial cycle and only retry those in subsequent attempts.
> > But this will add complexity to the implementation.
> >
>
> There will be some additional code for this but overall it improves
> the code in the lower level functions. We may want to use the existing
> remote_slot list for this purpose.
>
> The current proposed change in low-level functions appears to be
> difficult to maintain, especially the change proposed in
> update_and_persist_local_synced_slot(). If we can find a better way to
> achieve the same then we can consider the current approach as well.

Right. I've reworked the design to have the wait at a much lower
level. I've also used a single WAIT EVENT -
REPLICATION_SLOTSYNC_PRIMARY_CATCHUP for both the slotsync worker and
the sync API.

regards,
Ajin Cherian
Fujitsu Australia