IPC: LogicalParallelApplyStateChange
Waiting for a logical replication parallel apply process to change state
PostgreSQL wait event dossier
ClassIPC
Event
LogicalParallelApplyStateChange
VersionsPG 16-18
Evidence2 source location(s)
Official description
Waiting for a logical replication parallel apply process to change state
| PG 13 | PG 14 | PG 15 | PG 16 | PG 17 | PG 18 |
|---|---|---|---|---|---|
| — | — | — | ✓ | ✓ | ✓ |
Trigger mechanism
WAIT_EVENT_LOGICAL_PARALLEL_APPLY_STATE_CHANGE at src/backend/replication/logical/applyparallelworker.c:1276 is the grep-verified reporting path. The public identity/resource is mapped at src/backend/utils/activity/wait_event_names.txt:136. The instrumented operation is: Waiting for a logical replication parallel apply process to change state. The LogicalParallelApplyStateChange path has reached a process-coordination point and sleeps until a peer, worker, barrier, queue, or replication phase signals progress.
Normal or trouble?
- Normal: Brief rendezvous is normal when every participant continues to advance.
- Investigate: Investigate when the same phase persists across three samples, the expected peer is absent or blocked, or a queue and its dependants stop moving.
Diagnostic SQL
Sessions waiting on IPC/LogicalParallelApplyStateChange
Current IPC cohort
Lock and relation context for these sessions
Response
- Identify the peer or phase named by the event.
- Inspect that participant’s wait, error, and progress state.
- Repair the stalled participant or upstream dependency instead of treating the waiter as the root cause.
Source evidence
- PostgreSQL 18.6 · src/backend/replication/logical/applyparallelworker.c:1276 —
WAIT_EVENT_LOGICAL_PARALLEL_APPLY_STATE_CHANGE - PostgreSQL 18.6 · src/backend/utils/activity/wait_event_names.txt:136 —
LOGICAL_PARALLEL_APPLY_STATE_CHANGE
Related controls and signals
- GUCs: None directly.
- Metrics: [metric:waiting_sessions] · [metric:wait_event_share]