Horton

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

Ajin Cherian <itsajin@gmail.com>

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From: Ajin Cherian <itsajin@gmail.com>
To: shveta malik <shveta.malik@gmail.com>
Cc: Japin Li <japinli@hotmail.com>, Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>, Ashutosh Sharma <ashu.coek88@gmail.com>, Amit Kapila <amit.kapila16@gmail.com>, PostgreSQL mailing lists <pgsql-hackers@postgresql.org>
Date: 2025-11-06T07:53:02Z
Lists: pgsql-hackers

Commits

Same data as JSON: GET /api/v1/messages/:b64id/commits the thread's linked commits as JSON, with link sources. API reference →

  1. Enhance slot synchronization API to respect promotion signal.

  2. Fix inconsistent elevel in pg_sync_replication_slots() retry logic.

  3. Refactor slot synchronization logic in slotsync.c.

  4. Fix intermittent BF failure in 040_standby_failover_slots_sync.

  5. Add retry logic to pg_sync_replication_slots().

  6. Fix LOCK_TIMEOUT handling in slotsync worker.

  7. Add slotsync skip statistics.

Attachments

On Tue, Nov 4, 2025 at 5:23 PM shveta malik <shveta.malik@gmail.com> wrote:
>
> >
> > I have addressed the above comments in patch v21.
> >
>
> Thank You. Please find a few comments:
>
> 1)
> + fparams.slot_names = slot_names = NIL;
>
> I think it is not needed to set slot_names to NIL.
>
> 2)
> -    WAIT_EVENT_REPLICATION_SLOTSYNC_MAIN);
> +    WAIT_EVENT_REPLICATION_SLOTSYNC_PRIMARY_CATCHUP);
>
> The new name does not seem appropriate. For the slotsync-worker case,
> even when the primary is not behind, the worker still waits but it is
> not waiting for primary to catch-up. I could not find a better name
> except the original one 'WAIT_EVENT_REPLICATION_SLOTSYNC_MAIN'. We can
> change the explanation to :
>
> "Waiting in main loop of slot sync worker and slot sync API."
> Or
> "Waiting in main loop of slot synchronization."
>
> If anyone has any better name suggestions, we can consider changing.

Changed as suggested above.

>
> 3)
>
> +# Attempt to synchronize slots using API. The API will continue retrying
> +# synchronization until the remote slot catches up with the locally reserved
> +# position. The API will not return until this happens, to be able to make
> +# further calls, call the API in a background process.
>
> Shall we remove 'with the locally reserved position', it’s already
> explained in the test header and the comment is good enough even
> without it.
>

Changed.

> 4)
> +# Confirm log that the slot has been synced after becoming sync-ready.
>
> Shall we just say:
> Confirm from the log that the slot is sync-ready now.
>
> 5)
>  # Synchronize the primary server slots to the standby.
>  $standby1->safe_psql('postgres', "SELECT pg_sync_replication_slots();");
> @@ -945,6 +1007,7 @@ $subscriber1->safe_psql('postgres',
>  is( $standby1->safe_psql(
>   'postgres',
>   q{SELECT count(*) = 2 FROM pg_replication_slots WHERE slot_name IN
> ('lsub1_slot', 'snap_test_slot') AND synced AND NOT temporary;}
> +
>   ),
>
> Redundant change.

Removed.

Attaching patch v22 addressing the above comments.

regards,
Ajin Cherian
Fujitsu Australia