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Drop replication origin slots before tablesync worker exits.

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Currently, the replication origin tracking of the tablesync worker is
dropped by the apply worker. So, there will be a small lag between the
tablesync worker exit and its origin tracking got removed. In the
meantime, new tablesync workers can be launched and will try to set up
a new origin tracking. This can lead the system to reach max configured
limit (max_replication_slots) even if the user has configured the max
limit considering the number of tablesync workers required in the system.

We decided not to back-patch as this can occur in very narrow
circumstances and users have to option to increase the configured limit by
increasing max_replication_slots.

Reported-by: Hubert Depesz Lubaczewski
Author: Ajin Cherian
Reviwed-by: Masahiko Sawada, Peter Smith, Hou Zhijie, Amit Kapila
Discussion: https://postgr.es/m/20220714115155.GA5439@depesz.com
This commit is contained in:
Amit Kapila
2022-08-30 08:51:41 +05:30
parent 865424627d
commit f6c5edb8ab
2 changed files with 41 additions and 34 deletions
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25
src/backend/commands/subscriptioncmds.c
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@ -919,10 +919,10 @@ AlterSubscription_refresh(Subscription *sub, bool copy_data,
logicalrep_worker_stop(sub->oid, relid);
/*
* For READY state, we would have already dropped the
* tablesync origin.
* For READY state and SYNCDONE state, we would have already
* dropped the tablesync origin.
*/
if (state != SUBREL_STATE_READY)
if (state != SUBREL_STATE_READY && state != SUBREL_STATE_SYNCDONE)
{
char originname[NAMEDATALEN];
@ -930,11 +930,8 @@ AlterSubscription_refresh(Subscription *sub, bool copy_data,
* Drop the tablesync's origin tracking if exists.
*
* It is possible that the origin is not yet created for
* tablesync worker, this can happen for the states before
* SUBREL_STATE_FINISHEDCOPY. The apply worker can also
* concurrently try to drop the origin and by this time
* the origin might be already removed. For these reasons,
* passing missing_ok = true.
* tablesync worker so passing missing_ok = true. This can
* happen for the states before SUBREL_STATE_FINISHEDCOPY.
*/
ReplicationOriginNameForTablesync(sub->oid, relid, originname,
sizeof(originname));
@ -1507,13 +1504,19 @@ DropSubscription(DropSubscriptionStmt *stmt, bool isTopLevel)
/*
* Drop the tablesync's origin tracking if exists.
*
* For SYNCDONE/READY states, the tablesync origin tracking is known
* to have already been dropped by the tablesync worker.
*
* It is possible that the origin is not yet created for tablesync
* worker so passing missing_ok = true. This can happen for the states
* before SUBREL_STATE_FINISHEDCOPY.
*/
ReplicationOriginNameForTablesync(subid, relid, originname,
sizeof(originname));
replorigin_drop_by_name(originname, true, false);
if (rstate->state != SUBREL_STATE_SYNCDONE)
{
ReplicationOriginNameForTablesync(subid, relid, originname,
sizeof(originname));
replorigin_drop_by_name(originname, true, false);
}
}
/* Clean up dependencies */