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

From: Ashutosh Bapat <ashutosh(dot)bapat(dot)oss(at)gmail(dot)com>
To: shveta malik <shveta(dot)malik(at)gmail(dot)com>
Cc: Ajin Cherian <itsajin(at)gmail(dot)com>, Amit Kapila <amit(dot)kapila16(at)gmail(dot)com>, PostgreSQL mailing lists <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: Improve pg_sync_replication_slots() to wait for primary to advance
Date: 2025-08-08 13:21:59
Message-ID: CAExHW5tbUp0uZ_VJc2a210L8YTt8i86S_HRRoNG_LzLJ9suFDA@mail.gmail.com
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On Wed, Aug 6, 2025 at 8:48 AM shveta malik <shveta(dot)malik(at)gmail(dot)com> wrote:
>
> On Wed, Aug 6, 2025 at 7:35 AM Ajin Cherian <itsajin(at)gmail(dot)com> wrote:
> >
> > 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.
> > >
> >
> > Next patch, I'll work on addressing this comment. I'll need to
> > restructure the code to make this happen.
> >
>
> Okay, thanks Ajin. I will resume review after this comment is
> addressed as I am assuming that the new logic will get rid of most of
> the current wait logic and thus it makes sense to review it after it
> is addressed.

There's also a minor merge conflict because func.sgml is not split
into multiple files.

--
Best Wishes,
Ashutosh Bapat

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