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: "Zhijie Hou (Fujitsu)" <houzj(dot)fnst(at)fujitsu(dot)com>
Cc: shveta malik <shveta(dot)malik(at)gmail(dot)com>, "Hayato Kuroda (Fujitsu)" <kuroda(dot)hayato(at)fujitsu(dot)com>, Amit Kapila <amit(dot)kapila16(at)gmail(dot)com>, PostgreSQL Hackers <pgsql-hackers(at)lists(dot)postgresql(dot)org>, Ashutosh Sharma <ashu(dot)coek88(at)gmail(dot)com>
Subject: Re: How can end users know the cause of LR slot sync delays?
Date: 2025-11-26 09:51:17
Message-ID: CANhcyEVWyZBn=6knC4gKGOJZYCe2hzks-zPH=iqA3sfbkjjZAw@mail.gmail.com
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On Wed, 26 Nov 2025 at 14:23, Zhijie Hou (Fujitsu)
<houzj(dot)fnst(at)fujitsu(dot)com> wrote:
>
> On Wednesday, November 26, 2025 2:29 PM Shlok Kyal <shlok(dot)kyal(dot)oss(at)gmail(dot)com> wrote:
> > I have also addressed the remaining comments and attached the updated
> > patch.
>
> Thanks for updating the patch, I have few comments:
>
> 1.
> +/*
> + * Map a SlotSyncSkipReason enum to a human-readable string
> + */
> +static char *
> +GetSlotSyncSkipReasonName(SlotSyncSkipReason reason)
>
> Shall we add a static array to map the Enum value to the reason name
> instead of adding the following function ?
>
I think static array would be more clean and consistent with
ConflictTypeNames and SlotInvalidationCauses.
Made the changes for same.

> 2.
> + <literal>remote_behind</literal> means that the slot is ahead of the
> + corresponding failover slot on the primary.
>
> I think the current naming and doc is not easy for user to understand. So, I
> suggest mentioning the explicit reason of this skip, e.g., the required WALs and
> rows are removed or at the risk of removal. We can rename this reason to
> "wal_or_rows_removed" and make the document similar to the content in
> logicaldecoding.sgml.
>
I agree. Included the changes for same.

I have also addressed the comments by Shveta in [1].
[1]: https://www.postgresql.org/message-id/CAJpy0uDKC0QubC0pL%3DbZ4Qnq3eQbykLnFu5x%3DwmDkOmL44QL7g%40mail.gmail.com

Thanks,
Shlok Kyal

Attachment Content-Type Size
v14-0001-Add-slotsync_skip_reason-to-pg_replication_slots.patch application/octet-stream 15.1 KB

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