Postgresql 检查数据库主从复制进度的操作

如何查看主从复制的状态，且备库应用落后了多少字节

这些信息要在主库中查询

查看流复制的信息可以使用主库上的视图

select pid,state,client_addr,sync_priority,sync_state from pg_stat_replication;

pg_stat_replication中几个字断记录了发送wal的位置及备库接收到的wal的位置、

sent_location–发送wal的位置

write_location–备库接收到的wal的位置

flush_location—备库写wal日志到磁盘的位置

replay_location—备库应用日志的位置

查看备库落后主库多少字节

select pg_xlog_location_diff(pg_current_xlog_location(),replay_location)/1024/1024 as mb from pg_stat_replication;
select pg_xlog_location_diff(pg_current_xlog_location(),replay_location)/1024/1024/1024 as gb from pg_stat_replication;

级联复制

select pg_xlog_location_diff(pg_last_xlog_replay_location(),replay_location)/1024/1024/1024 as gb from pg_stat_replication;

补充：pgsql之查看主备复制延迟

查看复制延迟：

10.0及以上：

select 
  pg_wal_lsn_diff(a .c1, replay_lsn) /(1024 * 1024) as slave_latency_mb,
  pg_wal_lsn_diff(a .c1, sent_lsn) /(1024 * 1024) as send_latency_mb,
  pg_wal_lsn_diff(a .c1, flush_lsn) /(1024 * 1024) as flush_latency_mb,
  state,
  backend_start,
  now()::timestamp with time zone
 from pg_stat_replication, pg_current_wal_lsn() as a(c1)
 where client_addr='192.168.46.173' and application_name = 'standby1'
 order by slave_latency_mb, send_latency_mb desc
 limit 1;

注：

192.168.46.173 表示从库ip地址。

pg_wal_lsn_diff(lsn pg_lsn, lsn pg_lsn):计算两个预写式日志位置间的差别。

pg_current_wal_lsn()：获得当前预写式日志写入位置

小于10.0版本：

select 
  pg_xlog_location_diff(a .c1, replay_lsn) /(1024 * 1024) as slave_latency_mb,
  pg_xlog_location_diff(a .c1, sent_lsn) /(1024 * 1024) as send_latency_mb,
  pg_xlog_location_diff(a .c1, flush_lsn) /(1024 * 1024) as flush_latency_mb,
  state,
  backend_start,
  now()::timestamp with time zone
 from pg_stat_replication, pg_current_xlog_location as a(c1)
 where client_addr='192.168.46.173' and application_name = 'standby1'
 order by slave_latency_mb, send_latency_mb desc
 limit 1;

注：

192.168.46.173 表示从库ip地址。

pg_xlog_location_diff(lsn pg_lsn, lsn pg_lsn):计算两个预写式日志位置间的差别。

pg_current_xlog_location ()：获得当前预写式日志写入位置

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