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

Fujii Masao <masao.fujii@gmail.com>

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From: Fujii Masao <masao.fujii@gmail.com>
To: Amit Kapila <amit.kapila16@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: 2026-04-08T06:54:10Z
Lists: pgsql-hackers

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On Wed, Apr 8, 2026 at 12:36 PM Fujii Masao <masao.fujii@gmail.com> wrote:
> The backpatch added PROCSIG_SLOTSYNC_MESSAGE in the middle of enum
> ProcSignalReason, which could break the ABI. I’m planning to move it to
> the end of the enum in v17 and v18.
>
> That seems to work for v18. However, in v17, NUM_PROCSIGNALS is defined
> as the last enum value:
>
>             NUM_PROCSIGNALS /* Must be last! */
>         } ProcSignalReason;
>
> So simply moving PROCSIG_SLOTSYNC_MESSAGE to the end would change the meaning
> of NUM_PROCSIGNALS.
>
> One option might be to remove NUM_PROCSIGNALS from the enum, move
> PROCSIG_SLOTSYNC_MESSAGE to the end, and define it separately, e.g.
> #define NUM_PROCSIGNALS (PROCSIG_SLOTSYNC_MESSAGE + 1). Would that
> be acceptable without breaking the ABI? Thoughts?

The patches I'm planning to apply for v17 and v18 are attached.

For v17, I'm still not entirely sure this change is safe from an ABI
perspective. Even if it is, abi-compliance-check may still report
a break since the patch removes NUM_PROCSIGNALS from the enum
(defines it as separate macro). If so, we may need to update
.abi-compliance-history to avoid false positives.

Regards,

-- 
Fujii Masao

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.