Subject: Logical Replication Delay on Remote Server

From: Ramakrishna m <[email-masked]>
Date: Tue, 23 Apr 2024 22:55:40 +0530

Hi Team,

I am facing replication lag in postgres16 at times,not able to find the
reason.

Please find the configuration:
1) Two replication slots for two servers (1 is the same data center,
another remote)
2) weekly once/twice facing lag(around 2GB for 1k TPS environment) in the
remote   replication slot and another same data center server slot with 0
lag.

My observation:

1) Noticed pg_stat_replication_slot total_txn reduced from 1k to 5 or 6 but
other  slot is same with 1k TPS
2)And noticed lag for remote slot but fine with same data center
3) Most importantly I have plenty of Bandwidth available in n/w ,2GB is
still freely available out of 4GB network.
4)No IO issues on servers
I am not able to prove if this is due to Network .Can you help me how to
proceed on this?
At Least how the logical decoding total_txn is counting the view
pg_stat_replication_slot?

-- 
Thanks & Regards,
Ram.

---

From: Ramakrishna m <[email-masked]>
Date: Wed, 24 Apr 2024 08:10:20 +0530

Hi Team,

adding one more point here,

 5. Pg_stat_replication_slot  total_txn count reduces when lag occurs .Does
decoding stop in case of logical replication delay?

On Tue, 23 Apr 2024 at 22:55, Ramakrishna m <[email-masked]> wrote:

> 1) Noticed pg_stat_replication_slot total_txn reduced from 1k to 5 or 6
> but other  slot is same with 1k TPS

-- 
Thanks & Regards,
Ram.