Re: Standby node using replication slot not visible in pg_stat_replication while catching up

Hi,

On 2014-03-10 21:06:53 +0900, Michael Paquier wrote:
> I have been playing a bit with the replication slots, and I noticed a
> weird behavior in such a scenario:
> 1) Create a master/slave cluster, and have slave use a replication slot
> 2) Stop the master
> 3) Create a certain amount of WAL, during my tests I played with 4~5GB of WAL
> 4) Restart the slave, it catches up with the WALs that master has
> retained in pg_xlog.
> I noticed that while the standby using the replication slot catches
> up, it is not visible in pg_stat_replication on master. This makes
> monitoring of the replication lag difficult to follow, particularly in
> the case where the standby disconnects from the master. Once the
> standby has caught up, it reappears once again in pg_stat_replication.
> I didn't have a look at the code to see what is happening, but is this
> behavior expected?

Does the use of replication slots actually alter the behaviour? I don't
see how the slot code could influence things to that degree here. Could
it be that it's just restoring code from the standby's pg_xlog or using
restore_command?

Greetings,

Andres Freund

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