Re: How can end users know the cause of LR slot sync delays?

From: Shlok Kyal <shlok(dot)kyal(dot)oss(at)gmail(dot)com>
To: Amit Kapila <amit(dot)kapila16(at)gmail(dot)com>
Cc: Ashutosh Sharma <ashu(dot)coek88(at)gmail(dot)com>, "Hayato Kuroda (Fujitsu)" <kuroda(dot)hayato(at)fujitsu(dot)com>, PostgreSQL Hackers <pgsql-hackers(at)lists(dot)postgresql(dot)org>
Subject: Re: How can end users know the cause of LR slot sync delays?
Date: 2025-09-24 11:10:40
Message-ID: CANhcyEVW1qVRvyr=79upYxz=UtHvS1Kt+Dqd5HA6Qi49_jNfRg@mail.gmail.com
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On Thu, 18 Sept 2025 at 11:31, Amit Kapila <amit(dot)kapila16(at)gmail(dot)com> wrote:
>
> On Wed, Sep 17, 2025 at 8:19 PM Ashutosh Sharma <ashu(dot)coek88(at)gmail(dot)com> wrote:
> >
> > On Wed, Sep 17, 2025 at 5:14 PM Amit Kapila <amit(dot)kapila16(at)gmail(dot)com> wrote:
> > >
> > > On Wed, Sep 17, 2025 at 4:24 PM Hayato Kuroda (Fujitsu)
> > > <kuroda(dot)hayato(at)fujitsu(dot)com> wrote:
> > > >
> > > > Dear Shlok,
> > > >
> > > > Thanks for creating the patch. Personally I prefer approach2; approach1 cannot
> > > > indicate the current status of synchronization, it just shows the history.
> > > > I feel approach2 has more information than approach1.
> > > >
> > >
> > > I also think so but Ashutosh thought that it would be hacky. Ashutosh,
> > > did you have an opinion on this matter after seeing the patches?
> > >
> >
> > Yes, I’ve looked into both the patches. Approach 1 seems quite
> > straightforward. In approach 2, we need to pass some additional
> > arguments to update_local_sync_slot and
> > update_and_persist_local_synced_slot, which makes it feel a little
> > less clean compared to approach 1, where we simply add a new function
> > and call it directly.
> >
>
> This is because the approach-1 doesn't show the latest value of
> sync_status. I mean in the latest cycle if the sync is successful, it
> won't update the stats which I am not sure is correct because users
> may want to know the recent status of sync cycle. Otherwise, the patch
> should be almost the same. I think we can even try to write a patch
> for approach-2 without an additional out parameter in some of the
> functions.
>
Hi Amit,

I have written a patch which removes passing this extra parameter to
the functions.
I have attached the latest patch in [1].

[1]: https://www.postgresql.org/message-id/CANhcyEVFZN2Mkjs0QHshKm2_3AkQ0eufjkD12eL2MeuVkPyGbw%40mail.gmail.com

Thanks,
Shlok Kyal

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