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Fix LOCK_TIMEOUT handling during parallel apply.

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Previously, the parallel apply worker used SIGINT to receive a graceful
shutdown signal from the leader apply worker. However, SIGINT is also used
by the LOCK_TIMEOUT handler to trigger a query-cancel interrupt. This
overlap caused the parallel apply worker to miss LOCK_TIMEOUT signals,
leading to incorrect behavior during lock wait/contention.

This patch resolves the conflict by switching the graceful shutdown signal
from SIGINT to SIGUSR2.

Reported-by: Zane Duffield <duffieldzane@gmail.com>
Diagnosed-by: Zhijie Hou <houzj.fnst@fujitsu.com>
Author: Hayato Kuroda <kuroda.hayato@fujitsu.com>
Reviewed-by: Amit Kapila <amit.kapila16@gmail.com>
Backpatch-through: 16, where it was introduced
Discussion: https://postgr.es/m/CACMiCkXyC4au74kvE2g6Y=mCEF8X6r-Ne_ty4r7qWkUjRE4+oQ@mail.gmail.com
This commit is contained in:
Amit Kapila
2025-09-24 04:00:15 +00:00
parent 178bbf403c
commit 37fc5de438
3 changed files with 16 additions and 10 deletions
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5
src/backend/postmaster/interrupt.c
View File

@@ -94,9 +94,8 @@ SignalHandlerForCrashExit(SIGNAL_ARGS)
* shut down and exit.
*
* Typically, this handler would be used for SIGTERM, but some processes use
* other signals. In particular, the checkpointer exits on SIGUSR2, and the WAL
* writer and the logical replication parallel apply worker exits on either
* SIGINT or SIGTERM.
* other signals. In particular, the checkpointer and parallel apply worker
* exit on SIGUSR2, and the WAL writer exits on either SIGINT or SIGTERM.
*
* ShutdownRequestPending should be checked at a convenient place within the
* main loop, or else the main loop should call ProcessMainLoopInterrupts.

17
src/backend/replication/logical/applyparallelworker.c
View File

@@ -869,10 +869,17 @@ ParallelApplyWorkerMain(Datum main_arg)
InitializingApplyWorker = true;
/* Setup signal handling. */
/*
* Setup signal handling.
*
* Note: We intentionally used SIGUSR2 to trigger a graceful shutdown
* initiated by the leader apply worker. This helps to differentiate it
* from the case where we abort the current transaction and exit on
* receiving SIGTERM.
*/
pqsignal(SIGHUP, SignalHandlerForConfigReload);
pqsignal(SIGINT, SignalHandlerForShutdownRequest);
pqsignal(SIGTERM, die);
pqsignal(SIGUSR2, SignalHandlerForShutdownRequest);
BackgroundWorkerUnblockSignals();
/*
@@ -971,9 +978,9 @@ ParallelApplyWorkerMain(Datum main_arg)
/*
* The parallel apply worker must not get here because the parallel apply
* worker will only stop when it receives a SIGTERM or SIGINT from the
* leader, or when there is an error. None of these cases will allow the
* code to reach here.
* worker will only stop when it receives a SIGTERM or SIGUSR2 from the
* leader, or SIGINT from itself, or when there is an error. None of these
* cases will allow the code to reach here.
*/
Assert(false);
}

4
src/backend/replication/logical/launcher.c
View File

@@ -636,7 +636,7 @@ logicalrep_worker_stop(Oid subid, Oid relid)
/*
* Stop the given logical replication parallel apply worker.
*
* Node that the function sends SIGINT instead of SIGTERM to the parallel apply
* Node that the function sends SIGUSR2 instead of SIGTERM to the parallel apply
* worker so that the worker exits cleanly.
*/
void
@@ -674,7 +674,7 @@ logicalrep_pa_worker_stop(ParallelApplyWorkerInfo *winfo)
* Only stop the worker if the generation matches and the worker is alive.
*/
if (worker->generation == generation && worker->proc)
logicalrep_worker_stop_internal(worker, SIGINT);
logicalrep_worker_stop_internal(worker, SIGUSR2);
LWLockRelease(LogicalRepWorkerLock);
}