Re: postgrsql 9.5: Old WAL files remain in secondary `pg_xlog`

[vignesh kumar <vigneshkumar.venugopal@xxxxxxxxxxx>]

You can use slot based replication, so that postgres knows which WAL FILE to retain and delete. however, if you're not concerned about storage, but then the replica go for WAL storage or WAL hub kind of solutions.. 

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From: Kashif Zeeshan <kashi.zeeshan@xxxxxxxxx>
Sent: Sunday, June 2, 2024 5:17:57 PM
To: mohan.nbs.ont@xxxxxxxxx <mohan.nbs.ont@xxxxxxxxx>
Cc: pgsql-admin@xxxxxxxxxxxxxxxxxxxx <pgsql-admin@xxxxxxxxxxxxxxxxxxxx>
Subject: Re: postgrsql 9.5: Old WAL files remain in secondary `pg_xlog`

 

Hi Mohsn

There can be multiple reasons for that.

1. If the archiving process on the standby is not working correctly, old WAL files will not be removed.

2. Ensure that the configuration settings for WAL management are correctly set on both primary and standby

3. If checkpoints are not happening frequently enough, WAL files will accumulate.

To diagnose the issue

1. Ensure that the replication between the primary and the standby is working correctly.

On Primary Server

SELECT client_addr, state, sent_lsn, write_lsn, flush_lsn, replay_lsn
FROM pg_stat_replication;

On Standby Server

SELECT pg_last_wal_receive_lsn(), pg_last_wal_replay_lsn();

2. Check if the archiving process on the standby is working properly. Look for any errors or warnings in the PostgreSQL logs related to WAL archiving.

3. Ensure that the standby server has the correct restore command configured to fetch the archived WAL files.

Regards

Kashif Zeeshan

Bitnine Global

On Sat, Jun 1, 2024 at 4:01 AM Mohan NBSPS <mohan.nbs.ont@xxxxxxxxx> wrote:

Hello Community,

Although the WAL retaining settings are default (max size 1GB),

`wal_keep_segments` is 25, checkpoint target is 2.5 minutes(default).

I noticed a few WAL files in secondary nodes (streaming replication) `pg_xlog`

folder.

What could be the reason why postgresql did not delete these ?

Thank you

Regards

Mohan