Hey,
I'm happy postgresql user. Today I want to achieve a SQL query to add in our health check system. Sometimes we change our leader server in a hot-standby platform, so the timeline changes and the followers stop to receive wal data under timeline problems.
This is the log message:
`timeline 4 forked off current database system timeline 3 before current recovery point 0/84000098`
If I restart, this is going to work correctly. But I want to make an SQL query (in the follower) to now if replication is working or not. Nowadays I'm using this:
```
SELECT
CASE
WHEN pg_last_xlog_receive_location() = pg_last_xlog_replay_location() THEN 0
ELSE EXTRACT (EPOCH FROM now() - pg_last_xact_replay_timestamp())::INTEGER
END
AS replication_lag;
```
So, if the timeline is different, the result of the lag in replication is always 0. So I can't monitor that the server is in another TL.
Any idea? I tried pg_xlogfile_name() but can't be used during the recovery. Any idea?
PS: From the leader and pg_stat_replication can't get that it's not sync too.
Regards
