public inbox for [email protected]  

help / color / mirror / Atom feed

From: Laurenz Albe <[email protected]>
To: Subramanian,Ramachandran <[email protected]>
To: [email protected] <[email protected]>
Subject: Re: AW: AW: AW: Replication Testing- How to introduce a Lag
Date: Mon, 23 Mar 2026 15:33:29 +0100
Message-ID: <[email protected]> (raw)
In-Reply-To: <[email protected]>
References: <[email protected]>
	<[email protected]>
	<[email protected]>
	<[email protected]>
	<[email protected]>
	<[email protected]>
	<[email protected]>

On Mon, 2026-03-23 at 05:55 +0000, Subramanian,Ramachandran wrote:
> Thank you so much for your guidance,  Today morning I noticed the columns being null .  
> 
> > streaming | 0/491179E8 | 0/491179E8 | 0/491179E8 | 0/491179E8 |           |           |            |
> 
> Does it make sense to use the below SQL as a primary health check ?
> 
> [postgres@Source_server~]$ psql -p 5432 -c " select  pg_wal_lsn_diff(sent_lsn,replay_lsn) from pg_stat_replication"
>  pg_wal_lsn_diff
> -----------------
>                0
> (1 row)

No; you want to measure the lag between the primary's current WAL position and
what was already replayed on the standby:

  SELECT pg_wal_lsn_diff(pg_current_wal_lsn(), replay_lsn)
  FROM pg_stat_replication;

Yours,
Laurenz Albe

view thread (16+ messages)  latest in thread

reply

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Reply to all the recipients using the --to and --cc options:
  reply via email

  To: [email protected]
  Cc: [email protected], [email protected], [email protected]
  Subject: Re: AW: AW: AW: Replication Testing- How to introduce a Lag
  In-Reply-To: <[email protected]>

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

This inbox is served by agora; see mirroring instructions
for how to clone and mirror all data and code used for this inbox