Hi all, When recovery conflicts happen on the streaming replication standby, the wait event of startup process is null when max_standby_streaming_delay = 0 (to be exact, when the limit time calculated by max_standby_streaming_delay is behind the last WAL data receipt time is behind). Moreover the process title of waiting startup process looks odd in the case of lock conflicts.
1. When max_standby_streaming_delay > 0 and the startup process conflicts with a lock, * wait event backend_type | wait_event_type | wait_event --------------+-----------------+------------ startup | Lock | relation (1 row) * ps 42513 ?? Ss 0:00.05 postgres: startup recovering 000000010000000000000003 waiting Looks good. 2. When max_standby_streaming_delay > 0 and the startup process conflicts with a snapshot, * wait event backend_type | wait_event_type | wait_event --------------+-----------------+------------ startup | | (1 row) * ps 44299 ?? Ss 0:00.05 postgres: startup recovering 000000010000000000000003 waiting wait_event_type and wait_event are null in spite of waiting for conflict resolution. 3. When max_standby_streaming_delay > 0 and the startup process conflicts with a lock, * wait event backend_type | wait_event_type | wait_event --------------+-----------------+------------ startup | | (1 row) * ps 46510 ?? Ss 0:00.05 postgres: startup recovering 000000010000000000000003 waiting waiting wait_event_type and wait_event are null and the process title is wrong; "waiting" appears twice. The cause of the first problem, wait_event_type and wait_event are not set, is that WaitExceedsMaxStandbyDelay which is called by ResolveRecoveryConflictWithVirtualXIDs waits for other transactions using pg_usleep rather than WaitLatch. I think we can change it so that it uses WaitLatch and those caller passes wait event information. For the second problem, wrong process title, the cause is also relevant with ResolveRecoveryConflictWithVirtualXIDs; in case of lock conflicts we add "waiting" to the process title in WaitOnLock but we add it again in ResolveRecoveryConflictWithVirtualXIDs. I think we can have WaitOnLock not set process title in recovery case. This problem exists on 12, 11 and 10. I'll submit the patch. Regards, -- Masahiko Sawada http://www.2ndQuadrant.com/ PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services
