database/postgres
1
0
Fork 0
mirror of https://github.com/postgres/postgres.git synced 2025-06-11 20:28:21 +03:00
Code Activity

Prevent logical rep workers with removed subscriptions from starting.

Browse Source 
Any logical rep workers must have their subscription entries in
pg_subscription. To ensure this, we need to prevent the launcher
from starting new worker corresponding to the subscription that
DROP SUBSCRIPTION command is removing. To implement this,
previously LogicalRepLauncherLock was introduced and held until
the end of transaction running DROP SUBSCRIPTION. But using
LWLock for that purpose was not valid.

Instead, this commit changes DROP SUBSCRIPTION so that it takes
AccessExclusiveLock on pg_subscription, in order to ensure that
the launcher cannot see any subscriptions being removed. Also this
commit gets rid of LogicalRepLauncherLock.

Patch by me, reviewed by Petr Jelinek

Discussion: https://www.postgresql.org/message-id/CAHGQGwHPi8ky-yANFfe0sgmhKtsYcQLTnKx07bW9S7-Rn1746w@mail.gmail.com
This commit is contained in:
Fujii Masao
2017-03-09 01:44:23 +09:00
parent a9f66f9253
commit 4eafdcc276
3 changed files with 7 additions and 18 deletions
Download Patch File Download Diff File Expand all files Collapse all files

12
src/backend/commands/subscriptioncmds.c
View File

@ -461,7 +461,12 @@ DropSubscription(DropSubscriptionStmt *stmt, bool isTopLevel)
if (stmt->drop_slot)
PreventTransactionChain(isTopLevel, "DROP SUBSCRIPTION ... DROP SLOT");
rel = heap_open(SubscriptionRelationId, RowExclusiveLock);
/*
* Lock pg_subscription with AccessExclusiveLock to ensure
* that the launcher doesn't restart new worker during dropping
* the subscription
*/
rel = heap_open(SubscriptionRelationId, AccessExclusiveLock);
tup = SearchSysCache2(SUBSCRIPTIONNAME, MyDatabaseId,
CStringGetDatum(stmt->subname));
@ -528,14 +533,9 @@ DropSubscription(DropSubscriptionStmt *stmt, bool isTopLevel)
/* Clean up dependencies */
deleteSharedDependencyRecordsFor(SubscriptionRelationId, subid, 0);
/* Protect against launcher restarting the worker. */
LWLockAcquire(LogicalRepLauncherLock, LW_EXCLUSIVE);
/* Kill the apply worker so that the slot becomes accessible. */
logicalrep_worker_stop(subid);
LWLockRelease(LogicalRepLauncherLock);
/* Remove the origin tracking if exists. */
snprintf(originname, sizeof(originname), "pg_%u", subid);
originid = replorigin_by_name(originname, true);