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Commit799f8bc

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Shorten timeouts while waiting for logicalrep worker slot attach/detach.
When waiting for a logical replication worker process to start or stop,we have to busy-wait until we see it add or remove itself from theLogicalRepWorker slot in shared memory. Those loops were using aone-second delay between checks, but on any reasonably modern machine, itdoesn't take more than a couple of msec for a worker to spawn or shut down.Reduce the loop delays to 10ms to avoid wasting quite so much time in therelated regression tests.In principle, a better solution would be to fix things so that the waitingprocess can be awakened via its latch at the right time. But that seemsconsiderably more invasive, which is undesirable for a post-beta fix.Worker start/stop performance likely isn't of huge interest anyway forproduction purposes, so we might not ever get around to it.In passing, rearrange the second wait loop in logicalrep_worker_stop()so that the lock is held at the top of the loop, thus saving one lockacquisition/release per call, and making it look more like the other loop.Discussion:https://postgr.es/m/30864.1498861103@sss.pgh.pa.us
1 parentef74e03 commit799f8bc

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‎src/backend/replication/logical/launcher.c

Lines changed: 17 additions & 18 deletions
Original file line numberDiff line numberDiff line change
@@ -201,11 +201,11 @@ WaitForReplicationWorkerAttach(LogicalRepWorker *worker,
201201

202202
/*
203203
* We need timeout because we generally don't get notified via latch
204-
* about the worker attach.
204+
* about the worker attach. But we don't expect to have to wait long.
205205
*/
206206
rc=WaitLatch(MyLatch,
207207
WL_LATCH_SET |WL_TIMEOUT |WL_POSTMASTER_DEATH,
208-
1000L,WAIT_EVENT_BGWORKER_STARTUP);
208+
10L,WAIT_EVENT_BGWORKER_STARTUP);
209209

210210
/* emergency bailout if postmaster has died */
211211
if (rc&WL_POSTMASTER_DEATH)
@@ -408,8 +408,8 @@ logicalrep_worker_launch(Oid dbid, Oid subid, const char *subname, Oid userid,
408408
}
409409

410410
/*
411-
* Stop the logical replication workerand wait until it detaches from the
412-
* slot.
411+
* Stop the logical replication workerfor subid/relid, if any, and wait until
412+
*it detaches from theslot.
413413
*/
414414
void
415415
logicalrep_worker_stop(Oidsubid,Oidrelid)
@@ -435,19 +435,19 @@ logicalrep_worker_stop(Oid subid, Oid relid)
435435
generation=worker->generation;
436436

437437
/*
438-
* If we found worker but it does not have proc set it isstarting up,
439-
* wait for it to finish and then kill it.
438+
* If we foundaworker but it does not have proc setthenit isstill
439+
*starting up;wait for it to finish starting and then kill it.
440440
*/
441441
while (worker->in_use&& !worker->proc)
442442
{
443443
intrc;
444444

445445
LWLockRelease(LogicalRepWorkerLock);
446446

447-
/* Waitfor signal. */
447+
/* Waita bit --- we don't expect to have to wait long. */
448448
rc=WaitLatch(MyLatch,
449449
WL_LATCH_SET |WL_TIMEOUT |WL_POSTMASTER_DEATH,
450-
1000L,WAIT_EVENT_BGWORKER_STARTUP);
450+
10L,WAIT_EVENT_BGWORKER_STARTUP);
451451

452452
/* emergency bailout if postmaster has died */
453453
if (rc&WL_POSTMASTER_DEATH)
@@ -459,7 +459,7 @@ logicalrep_worker_stop(Oid subid, Oid relid)
459459
CHECK_FOR_INTERRUPTS();
460460
}
461461

462-
/*Check worker status. */
462+
/*Recheck worker status. */
463463
LWLockAcquire(LogicalRepWorkerLock,LW_SHARED);
464464

465465
/*
@@ -480,27 +480,22 @@ logicalrep_worker_stop(Oid subid, Oid relid)
480480

481481
/* Now terminate the worker ... */
482482
kill(worker->proc->pid,SIGTERM);
483-
LWLockRelease(LogicalRepWorkerLock);
484483

485484
/* ... and wait for it to die. */
486485
for (;;)
487486
{
488487
intrc;
489488

490-
LWLockAcquire(LogicalRepWorkerLock,LW_SHARED);
489+
/* is it gone? */
491490
if (!worker->proc||worker->generation!=generation)
492-
{
493-
LWLockRelease(LogicalRepWorkerLock);
494491
break;
495-
}
496-
LWLockRelease(LogicalRepWorkerLock);
497492

498-
CHECK_FOR_INTERRUPTS();
493+
LWLockRelease(LogicalRepWorkerLock);
499494

500-
/* Waitfor more work. */
495+
/* Waita bit --- we don't expect to have to wait long. */
501496
rc=WaitLatch(MyLatch,
502497
WL_LATCH_SET |WL_TIMEOUT |WL_POSTMASTER_DEATH,
503-
1000L,WAIT_EVENT_BGWORKER_SHUTDOWN);
498+
10L,WAIT_EVENT_BGWORKER_SHUTDOWN);
504499

505500
/* emergency bailout if postmaster has died */
506501
if (rc&WL_POSTMASTER_DEATH)
@@ -511,7 +506,11 @@ logicalrep_worker_stop(Oid subid, Oid relid)
511506
ResetLatch(MyLatch);
512507
CHECK_FOR_INTERRUPTS();
513508
}
509+
510+
LWLockAcquire(LogicalRepWorkerLock,LW_SHARED);
514511
}
512+
513+
LWLockRelease(LogicalRepWorkerLock);
515514
}
516515

517516
/*

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