LWLock/SyncRep

各版本描述

相邻版本里类型、名称与英文描述都相同的合并成一段，旧的在前。中文取自图谱或本站手册译文，没有译文的只给英文原文。

1. 9.6

   LWLockNamed/SyncRepLock曾用名

   等待读取或更新同步副本的信息。

   Waiting to read or update information about synchronous replicas.

2. 10–12

   LWLock/SyncRepLock曾用名

   等待读取或更新同步副本的信息。

   Waiting to read or update information about synchronous replicas.

3. 13–20

   LWLock/SyncRep

   等待读取或更新有关同步复制状态的信息。

   Waiting to read or update information about the state of synchronous replication.

触发机制

SyncRepLock 保护同步复制队列与共享 sender 状态。提交会话入队或检查等待位置，WAL sender 则更新已被同步备库确认的 LSN。

SyncRepLock protects synchronous-replication queues and shared sender state. Committers enqueue or inspect their wait position while WAL senders update which LSNs the configured synchronous standbys have acknowledged.

诊断 SQL

直接在 psql 里跑；标注的是语句里用到的视图与列所要求的最低版本。

SELECT pid, backend_type, usename, datname, application_name,
       state, now() - query_start AS query_age,
       now() - xact_start AS xact_age,
       wait_event_type, wait_event,
       pg_blocking_pids(pid) AS blocking_pids,
       left(query, 160) AS query
FROM pg_stat_activity
WHERE wait_event_type = 'LWLock'
  AND wait_event = 'SyncRep'
ORDER BY query_age DESC NULLS LAST;

SELECT wait_event, count(*) AS waiting_sessions,
       count(*) FILTER (WHERE state = 'active') AS active_waiters,
       max(now() - query_start) AS oldest_query
FROM pg_stat_activity
WHERE wait_event_type = 'LWLock'
GROUP BY wait_event
ORDER BY waiting_sessions DESC, wait_event;

SELECT a.pid, l.locktype, l.mode, l.granted, l.fastpath,
       d.datname, n.nspname, c.relname,
       l.page, l.tuple, l.virtualxid, l.transactionid,
       l.classid, l.objid, l.objsubid
FROM pg_stat_activity AS a
LEFT JOIN pg_locks AS l ON l.pid = a.pid
LEFT JOIN pg_database AS d ON d.oid = l.database
LEFT JOIN pg_class AS c
  ON c.oid = l.relation
 AND l.database = (
       SELECT oid FROM pg_database WHERE datname = current_database()
     )
LEFT JOIN pg_namespace AS n ON n.oid = c.relnamespace
WHERE a.wait_event_type = 'LWLock'
  AND a.wait_event = 'SyncRep'
ORDER BY a.pid, l.granted, l.locktype, l.mode;

处置步骤

1. 区分 LWLock/SyncRep、IPC/SyncRep 与复制延迟等待。
2. 检查同步备库健康度、sender 抖动与提交速率。
3. 稳定复制并平滑提交突发；只有获得明确事故授权时才改变持久性策略。

相关参数与指标

synchronous_standby_namessynchronous_commitwal_sender_timeout waiting_sessionswait_event_sharereplication_flush_lagcommit_latency

源码证据

图谱在各版本源码树里核对到的位置，新的在前。「触发点」是真正上报等待事件的调用处，「目录定义」只说明这个名字在枚举里存在。

演化历史

相邻两个大版本之间的差异，新的在前。版本号链到该版的变动清单。

1. PostgreSQL 13 ← 12 更名

   更名 SyncRepLock→SyncRep 描述措辞更新

   等待读取或更新有关同步复制状态的信息。

   描述前后对照

   Waiting to read or update information about synchronous replicas. Waiting to read or update information about the state of synchronous replication.

2. PostgreSQL 10 ← 9.6 类型变动

   类型 LWLockNamed→LWLock

   等待读取或更新同步副本的信息。

3. PostgreSQL 9.6 新增此事件

   9.6 引入等待事件机制，此为本事件的首个版本

   等待读取或更新同步副本的信息。

同类事件