Re: Question regarding failover behavior

Updating to say I tested and ran into the issue where the timeline switched
from 0C to 0D.

Trying to bring the old primary back up as standby fails. It recovers upto
a point and then gets stuck asked for a next file that doesn't exist.

Regardless of taking the existing data directory or restoring a new
basebackup.

Taking a new basebackup, with the new primary, and restoring that, works.
Standby gets in sync and everything is as expected.

Kind regards,
Koen De Groote

On Wed, Aug 24, 2022 at 1:09 AM Koen De Groote <kdg(dot)dev(at)gmail(dot)com> wrote:

> Hello all,
>
> I have a system that was originally set up on 9.3, a few years ago moved
> to 11.2
>
> A shared mount is used to host the basebackup and wal archives.
>
> The failover procedure was basically manual and as follow:
>
> 1/ Take out the primary, remove the IP from the primary machine/VM
> 2/ Create the trigger_file on the standby, add the IP to the new primary
> machine/VM
> 3/ Create a basebackup from the new primary
> 4/ Redeploy the new standby, which will unpack this basebackup from step 3
> 5/ The new standby will have a restore_command to get synced back up.
>
> I see there's more recent tools like pg_rewind these days. Haven't had
> time to check that out and probably won't for a while.
>
> My question is: is the basebackup actually necessary? Can I not simply
> modify the configuration old the old primary, set it up like a standby, and
> then start the process/container, and have it pick up the necessary
> wal_archives with the restore_command?
>
> Or is it more complicated than that? Something like a timeline jump or
> something else that makes it impossible to simply set the old primary to
> standby and start it again?
>
> Kind regards,
> Koen De Groote
>