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Re: Use SIGTERM instead of SIGUSR1 for slotsync worker to exit during promotion?

Amit Kapila <amit.kapila16@gmail.com>

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From: Amit Kapila <amit.kapila16@gmail.com>
To: Fujii Masao <masao.fujii@gmail.com>
Cc: Nisha Moond <nisha.moond412@gmail.com>, "Zhijie Hou (Fujitsu)" <houzj.fnst@fujitsu.com>, shveta malik <shveta.malik@gmail.com>, PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>
Date: 2026-04-02T06:34:18Z
Lists: pgsql-hackers 
On Thu, Apr 2, 2026 at 10:31 AM Fujii Masao <masao.fujii@gmail.com> wrote:
>
> On Wed, Apr 1, 2026 at 8:11 PM Nisha Moond <nisha.moond412@gmail.com> wrote:
> > > As for backpatching, this looks like it should go back to v17, where slotsync
> > > was introduced. Thought?
> >
> > Right, the issue exists in v17 as well.
> >
> > Attached the updated patch.
>
> Thanks for updating the patch! LGTM.
>
> I noticed that commit 1362bc33e02 updated the slotsync code so that a backend
> performing slot synchronization is signaled on promotion, but it was applied
> only to master. I’m not sure why it wasn’t backpatched to v17 and v18,
>

It is because we added retry slot-sync logic for API in master in
commit 0d2d4a0ec3eca64e7f5ce7f7630b56a561b2663c. So, there is no
chance of API waiting except for the race condition being discussed
here.

> but it seems we need to backpatch it first before backpatching this patch.
> Thought?
>

I feel the use of API before this version was mainly for test-cases as
it was not production ready. So, it is less helpful to backpatch
1362bc33e02, if we want, we can backpatch only the worker part of the
fix. OTOH, as the issue is not frequent and we have some workaround
(at least for more common platforms) as well, we can consider not
backpatching it.

-- 
With Regards,
Amit Kapila.

Commits

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

  1. Update .abi-compliance-history for change to enum ProcSignalReason

  2. Fix ABI break by moving PROCSIG_SLOTSYNC_MESSAGE in ProcSignalReason

  3. Fix slotsync worker blocking promotion when stuck in wait

  4. Add retry logic to pg_sync_replication_slots().

  5. Enhance slot synchronization API to respect promotion signal.