Re: Patroni, slots, and expiring WALs

Hi,

On Tue, 28 Mar 2023 at 16:55, Peter J. Holzer <hjp-pgsql(at)hjp(dot)at> wrote:

>
> However, when we took down one node for about two hours for some tests
> recently (with some moderate traffic on the remaining node), the replica
> didn't catch up after being restarted and inspection of the logs showed
> that it was trying to get WALs which had already been deleted.
>

It is impossible to know whether it is down temporarily or gone forever,
therefore the slot is removed as soon as the member key expires (after TTL).

> So apparently, `use_slots: true` isn't enough. What else do I have to
> configure? (I know about wal_keep_size, but it was my understanding that
> this isn't needed when slots are used)
>

The best option is to configure continuous archiving and PITR. Backups are
always important.
The second option - you can put all member names into permanent slots
configuration (using patronictl edit-config):
slots:
nodename1:
type: physical
nodename2:
type: physical
nodename3:
type: physical

This way slots representing these members will not be removed.

Regards,
--
Alexander Kukushkin