Hi Andrey,
./wal-g7 --version
wal-g version v1.1.2-rc 6af461f 2021.12.14_08:19:15 PostgreSQL
The only probable problem I can imagine is that we open transaction during pg_stop_backup() [0] to set a statement_timeout
Do you think this will prevent the autovacuum from kicking in ?
I think this tx can be safely removed
How can I remove this? I can test whether this is the problem
Thanks,
Nikhil
On Thu, Jun 30, 2022 at 5:18 PM Andrey Borodin <x4mmm@xxxxxxxxxxxxxx> wrote:
Hi!
> On 30 Jun 2022, at 14:23, Nikhil Shetty <nikhil.dba04@xxxxxxxxx> wrote:
>
> Hi,
>
> PostgreSQL version - 11.7
>
> We are using wal-g for backup/restore. We had a duration of high WAL generation due to application usage due to which archive backup was delayed.
>
> Backup was started through cron schedule and it didn't complete because it waits for the last WAL to be archived. Now, I know that long running transactions will prevent vacuuming of dead tuples but in this case we were able to run manual vacuums successfully but auto-vacuum never starts.
>
> As soon as we terminated the long running backup session, the auto-vacuum started kicking in.
>
> Wanted to understand why a backup operation is blocking the auto-vacuum?
>
> Wal-g uses non-exclusive backups and waits for the last wal to be archived.
As far as I know, WAL-G should not prevent running autovacuums on tables. WAL-G can be run against replication standby, where vacuum is not possible at all, so there must be no conflicts...
The only probable problem I can imagine is that we open transaction during pg_stop_backup() [0] to set a statement_timeout. I think this is superflous and unneeded. I think this tx can be safely removed. But anyway, this tx does not have a xid (otherwise it could not run on Standby).
BTW which version of WAL-G do you use?
Best regards, Andrey Borodin.
[0] https://github.com/wal-g/wal-g/blob/8b9b3ca06efb44be4724208dc6f6d11836bd34d9/internal/databases/postgres/queryRunner.go#L243
