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

[Fujii Masao]

On Fri, Mar 27, 2026 at 9:38 PM Nisha Moond <nisha.moond...@gmail.com> wrote:
> Attached the updated patch.

Thanks for updating the patch! It looks good overall.

Regarding the comments in SlotSyncCtxStruct, since the role of
stopSignaled field has changed, those comments should be updated
accordingly? For example,

-------------------------
- * the SQL function pg_sync_replication_slots(). When the startup process sets
- * 'stopSignaled' during promotion, it uses this 'pid' to wake up the currently
- * synchronizing process so that the process can immediately stop its
- * synchronizing work on seeing 'stopSignaled' set.
- * Setting 'stopSignaled' is also used to handle the race condition when the
+ * the SQL function pg_sync_replication_slots(). On promotion,
+ * the startup process sets 'stopSignaled' and uses this 'pid' to wake up
+ * the currently synchronizing process so that the process can
+ * immediately stop its synchronizing work.
+ * Setting 'stopSignaled' is used to handle the race condition when the
-------------------------


+/*
+ * Interrupt flag set when PROCSIG_SLOTSYNC_MESSAGE is received, asking the
+ * slotsync worker or pg_sync_replication_slots() to stop because
+ * standby promotion has been triggered.
+ */
+volatile sig_atomic_t SlotSyncShutdown = false;

For the interrupt flag set in procsignal_sigusr1_handler(), other flags
use a *Pending suffix (e.g., ProcSignalBarrierPending,
ParallelApplyMessagePending), so SlotSyncShutdownPending would
be more consistent.


+void
+HandleSlotSyncMessage(void)

Functions called from ProcessInterrupts() typically use the Process* prefix
(e.g., ProcessProcSignalBarrier(), ProcessParallelApplyMessages()),
so ProcessSlotSyncMessage would be more consistent than HandleSlotSyncMessage.


+ ereport(LOG,
+ errmsg("replication slot synchronization worker will stop because
promotion is triggered"));
+
+ proc_exit(0);
+ }
+ else
+ {
+ /*
+ * For the backend executing SQL function
+ * pg_sync_replication_slots().
+ */
+ ereport(ERROR,
+ errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
+ errmsg("replication slot synchronization will stop because promotion
is triggered"));

The log messages say "will stop", but since sync hasn't started yet,
"will not start" seems clearer here. For example, "replication slot
synchronization worker will not start because promotion was triggered"
and "replication slot synchronization will not start because promotion was
triggered". Thought?

Regards,

-- 
Fujii Masao