Обсуждение: Wal file increase

On Sun, 2025-12-14 at 17:30 +0200, kasem adel wrote:
> Appreciate your usual support that we facing an issue when take pg_basebackup for 4 TB
> database in standby server and when backup finished we face huge number of wal file
> with huge size generated for 6 hours the cause replication interruption.

If you want help with that, you will have to give us enough information to explain what
happened.

- What exactly is a "replication interruption", and how do you diagnose it?

- Are you using streaming replication or logical replication?

- If it is streaming replication, are you using a replication slot?

- It is expected that if you suspend replication and have a replication slot, WAL will
  pile up on the primary.  But what is the connection with pg_basebackup?

Yours,
Laurenz Albe

On Mon, 2025-12-15 at 07:25 +0000, kasem adel wrote:
> Thanks for your support We have physical replication connection with Postgres node standby
> and have another replication slot with logical replication with another node and every day
> after run pg_basebackup we face huge number of file created and size per every hour is 23GB
> and in normal size is 0.8 GB and in logical replication we see in logs it’s in same
> checkpoint but baseline change and we run pg_basebackup with -X fetch -C fast.

pg_basebackup does not increase the WAL volume, except by the full-page images that get
written after any checkpoint.  So you'd need to find an explanation for that.

"-X fetch" is not a good choice.  Use "-X stream".

Anyway, you didn't answer all my questions.

Yours,
Laurenz Albe

On Mon, 2025-12-15 at 08:19 +0000, kasem adel wrote:
> > -What exactly is a "replication interruption", and how do you diagnose it?
> We see replication slot restart every time in these period

I have never heard of a "replication slot restart"...

> > - Are you using streaming replication or logical replication?
> I have streaming replication for one node and another logical replication 
> > - If it is streaming replication, are you using a replication slot?
> Yes have replication slot
> > - It is expected that if you suspend replication and have a replication slot, WAL will
> >   pile up on the primary.  But what is the connection with pg_basebackup?
> Yes still exist.

You probably need to hire an expert to have a look at your system and find
out what *really* is going on there.

Yours,
Laurenz Albe