diff options
| author | Amit Kapila | 2023-01-24 03:55:36 +0000 |
|---|---|---|
| committer | Amit Kapila | 2023-01-24 03:55:36 +0000 |
| commit | 6c6d6ba3ee2c160b53f727cf8e612014b316d6e4 (patch) | |
| tree | e2b20e5a6ad953cabaa6377eaba91d8d9e3ecea3 /src/backend | |
| parent | 728f86fec65537eade8d9e751961782ddb527934 (diff) | |
Fix the Drop Database hang.
The drop database command waits for the logical replication sync worker to
accept ProcSignalBarrier and the worker's slot creation waits for the drop
database to finish which leads to a deadlock. This happens because the
tablesync worker holds interrupts while creating a slot.
We prevent cancel/die interrupts while creating a slot in the table sync
worker because it is possible that before the server finishes this
command, a concurrent drop subscription happens which would complete
without removing this slot and that leads to the slot existing until the
end of walsender. However, the slot will eventually get dropped at the
walsender exit time, so there is no danger of the dangling slot.
This patch reallows cancel/die interrupts while creating a slot and
modifies the test to wait for slots to become zero to prevent finding an
ephemeral slot.
The reported hang doesn't happen in PG14 as the drop database starts to
wait for ProcSignalBarrier with PG15 (commits 4eb2176318 and e2f65f4255)
but it is good to backpatch this till PG14 as it is not a good idea to
prevent interrupts during a network call that could block indefinitely.
Reported-by: Lakshmi Narayanan Sreethar
Diagnosed-by: Andres Freund
Author: Hou Zhijie
Reviewed-by: Vignesh C, Amit Kapila
Backpatch-through: 14, where it was introduced in commit 6b67d72b60
Discussion: https://postgr.es/m/CA+kvmZELXQ4ZD3U=XCXuG3KvFgkuPoN1QrEj8c-rMRodrLOnsg@mail.gmail.com
Diffstat (limited to 'src/backend')
| -rw-r--r-- | src/backend/replication/logical/tablesync.c | 7 |
1 files changed, 0 insertions, 7 deletions
diff --git a/src/backend/replication/logical/tablesync.c b/src/backend/replication/logical/tablesync.c index 4647837b823..07eea504ba8 100644 --- a/src/backend/replication/logical/tablesync.c +++ b/src/backend/replication/logical/tablesync.c @@ -1396,17 +1396,10 @@ LogicalRepSyncTableStart(XLogRecPtr *origin_startpos) * Create a new permanent logical decoding slot. This slot will be used * for the catchup phase after COPY is done, so tell it to use the * snapshot to make the final data consistent. - * - * Prevent cancel/die interrupts while creating slot here because it is - * possible that before the server finishes this command, a concurrent - * drop subscription happens which would complete without removing this - * slot leading to a dangling slot on the server. */ - HOLD_INTERRUPTS(); walrcv_create_slot(LogRepWorkerWalRcvConn, slotname, false /* permanent */ , false /* two_phase */ , CRS_USE_SNAPSHOT, origin_startpos); - RESUME_INTERRUPTS(); /* * Setup replication origin tracking. The purpose of doing this before the |