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Commitf6c5edb

Browse files
author
Amit Kapila
committed
Drop replication origin slots before tablesync worker exits.
Currently, the replication origin tracking of the tablesync worker isdropped by the apply worker. So, there will be a small lag between thetablesync worker exit and its origin tracking got removed. In themeantime, new tablesync workers can be launched and will try to set upa new origin tracking. This can lead the system to reach max configuredlimit (max_replication_slots) even if the user has configured the maxlimit considering the number of tablesync workers required in the system.We decided not to back-patch as this can occur in very narrowcircumstances and users have to option to increase the configured limit byincreasing max_replication_slots.Reported-by: Hubert Depesz LubaczewskiAuthor: Ajin CherianReviwed-by: Masahiko Sawada, Peter Smith, Hou Zhijie, Amit KapilaDiscussion:https://postgr.es/m/20220714115155.GA5439@depesz.com
1 parent8654246 commitf6c5edb

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2 files changed

+41
-34
lines changed

2 files changed

+41
-34
lines changed

‎src/backend/commands/subscriptioncmds.c

Lines changed: 14 additions & 11 deletions
Original file line numberDiff line numberDiff line change
@@ -919,22 +919,19 @@ AlterSubscription_refresh(Subscription *sub, bool copy_data,
919919
logicalrep_worker_stop(sub->oid,relid);
920920

921921
/*
922-
* For READY state, we would have already dropped the
923-
* tablesync origin.
922+
* For READY state and SYNCDONE state, we would have already
923+
*dropped thetablesync origin.
924924
*/
925-
if (state!=SUBREL_STATE_READY)
925+
if (state!=SUBREL_STATE_READY&&state!=SUBREL_STATE_SYNCDONE)
926926
{
927927
charoriginname[NAMEDATALEN];
928928

929929
/*
930930
* Drop the tablesync's origin tracking if exists.
931931
*
932932
* It is possible that the origin is not yet created for
933-
* tablesync worker, this can happen for the states before
934-
* SUBREL_STATE_FINISHEDCOPY. The apply worker can also
935-
* concurrently try to drop the origin and by this time
936-
* the origin might be already removed. For these reasons,
937-
* passing missing_ok = true.
933+
* tablesync worker so passing missing_ok = true. This can
934+
* happen for the states before SUBREL_STATE_FINISHEDCOPY.
938935
*/
939936
ReplicationOriginNameForTablesync(sub->oid,relid,originname,
940937
sizeof(originname));
@@ -1507,13 +1504,19 @@ DropSubscription(DropSubscriptionStmt *stmt, bool isTopLevel)
15071504
/*
15081505
* Drop the tablesync's origin tracking if exists.
15091506
*
1507+
* For SYNCDONE/READY states, the tablesync origin tracking is known
1508+
* to have already been dropped by the tablesync worker.
1509+
*
15101510
* It is possible that the origin is not yet created for tablesync
15111511
* worker so passing missing_ok = true. This can happen for the states
15121512
* before SUBREL_STATE_FINISHEDCOPY.
15131513
*/
1514-
ReplicationOriginNameForTablesync(subid,relid,originname,
1515-
sizeof(originname));
1516-
replorigin_drop_by_name(originname, true, false);
1514+
if (rstate->state!=SUBREL_STATE_SYNCDONE)
1515+
{
1516+
ReplicationOriginNameForTablesync(subid,relid,originname,
1517+
sizeof(originname));
1518+
replorigin_drop_by_name(originname, true, false);
1519+
}
15171520
}
15181521

15191522
/* Clean up dependencies */

‎src/backend/replication/logical/tablesync.c

Lines changed: 27 additions & 23 deletions
Original file line numberDiff line numberDiff line change
@@ -291,6 +291,7 @@ process_syncing_tables_for_sync(XLogRecPtr current_lsn)
291291
{
292292
TimeLineIDtli;
293293
charsyncslotname[NAMEDATALEN]= {0};
294+
charoriginname[NAMEDATALEN]= {0};
294295

295296
MyLogicalRepWorker->relstate=SUBREL_STATE_SYNCDONE;
296297
MyLogicalRepWorker->relstate_lsn=current_lsn;
@@ -309,6 +310,30 @@ process_syncing_tables_for_sync(XLogRecPtr current_lsn)
309310
MyLogicalRepWorker->relstate,
310311
MyLogicalRepWorker->relstate_lsn);
311312

313+
/*
314+
* Cleanup the tablesync origin tracking.
315+
*
316+
* Resetting the origin session removes the ownership of the slot.
317+
* This is needed to allow the origin to be dropped.
318+
*/
319+
ReplicationOriginNameForTablesync(MyLogicalRepWorker->subid,
320+
MyLogicalRepWorker->relid,
321+
originname,
322+
sizeof(originname));
323+
replorigin_session_reset();
324+
replorigin_session_origin=InvalidRepOriginId;
325+
replorigin_session_origin_lsn=InvalidXLogRecPtr;
326+
replorigin_session_origin_timestamp=0;
327+
328+
/*
329+
* We expect that origin must be present. The concurrent operations
330+
* that remove origin like a refresh for the subscription take an
331+
* access exclusive lock on pg_subscription which prevent the previous
332+
* operation to update the rel state to SUBREL_STATE_SYNCDONE to
333+
* succeed.
334+
*/
335+
replorigin_drop_by_name(originname, false, false);
336+
312337
/*
313338
* End streaming so that LogRepWorkerWalRcvConn can be used to drop
314339
* the slot.
@@ -318,7 +343,7 @@ process_syncing_tables_for_sync(XLogRecPtr current_lsn)
318343
/*
319344
* Cleanup the tablesync slot.
320345
*
321-
* This has to be done afterupdatingthestate because otherwise if
346+
* This has to be done after thedata changes because otherwise if
322347
* there is an error while doing the database operations we won't be
323348
* able to rollback dropped slot.
324349
*/
@@ -441,8 +466,6 @@ process_syncing_tables_for_apply(XLogRecPtr current_lsn)
441466
*/
442467
if (current_lsn >=rstate->lsn)
443468
{
444-
charoriginname[NAMEDATALEN];
445-
446469
rstate->state=SUBREL_STATE_READY;
447470
rstate->lsn=current_lsn;
448471
if (!started_tx)
@@ -452,26 +475,7 @@ process_syncing_tables_for_apply(XLogRecPtr current_lsn)
452475
}
453476

454477
/*
455-
* Remove the tablesync origin tracking if exists.
456-
*
457-
* The normal case origin drop is done here instead of in the
458-
* process_syncing_tables_for_sync function because we don't
459-
* allow to drop the origin till the process owning the origin
460-
* is alive.
461-
*
462-
* There is a chance that the user is concurrently performing
463-
* refresh for the subscription where we remove the table
464-
* state and its origin and by this time the origin might be
465-
* already removed. So passing missing_ok = true.
466-
*/
467-
ReplicationOriginNameForTablesync(MyLogicalRepWorker->subid,
468-
rstate->relid,
469-
originname,
470-
sizeof(originname));
471-
replorigin_drop_by_name(originname, true, false);
472-
473-
/*
474-
* Update the state to READY only after the origin cleanup.
478+
* Update the state to READY.
475479
*/
476480
UpdateSubscriptionRelState(MyLogicalRepWorker->subid,
477481
rstate->relid,rstate->state,

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