Re: promotion related handling in pg_sync_replication_slots()

On Thu, Apr 4, 2024 at 5:17 PM Amit Kapila <amit(dot)kapila16(at)gmail(dot)com> wrote:
>
> On Thu, Apr 4, 2024 at 5:05 PM shveta malik <shveta(dot)malik(at)gmail(dot)com> wrote:
> >
> > Hello hackers,
> >
> > Currently, promotion related handling is missing in the slot sync SQL
> > function pg_sync_replication_slots(). Here is the background on how
> > it is done in slot sync worker:
> > During promotion, the startup process in order to shut down the
> > slot-sync worker, sets the 'stopSignaled' flag, sends the shut-down
> > signal, and waits for slot sync worker to exit. Meanwhile if the
> > postmaster has not noticed the promotion yet, it may end up restarting
> > slot sync worker. In such a case, the worker exits if 'stopSignaled'
> > is set.
> >
> > Since there is a chance that the user (or any of his scripts/tools)
> > may execute SQL function pg_sync_replication_slots() in parallel to
> > promotion, such handling is needed in this SQL function as well, The
> > attached patch attempts to implement the same.
> >
>
> Thanks for the report and patch. I'll look into it.
>

Please find v2. Changes are:
1) Rebased the patch as there was conflict due to recent commit 6f132ed.
2) Added an Assert in update_synced_slots_inactive_since() to ensure
that the slot does not have active_pid.
3) Improved commit msg and comments.

thanks
Shveta