[pgpool-hackers: 3269] Replication lag calculation by pgpool

[Abhijit Gharami]

Hi,

In our PostgreSQL setup, we have 2 PostgreSQL VMs(primary, standby) and 3
Pgpool VMs. During failover we check the replication lag. If the
replication lag is zero
then we proceed for failover. To check the replication lag we rely on
pgpool, command we use to check the lag is "show pool_nodes".
We extract the last column value of standby node entry.

We have couple question regarding the replication lag calculation. Please
help us here.
1 - Can we rely on this replication lag value incase  postgresql primary is
down?
2 - How Pgpool calculate the replication lag if primary VM is down?

Regards,
Abhijit
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