Re: Excessive number of replication slots for 12->14 logical replication

On Sat, Jul 16, 2022 at 3:44 AM Andres Freund <andres@anarazel.de> wrote:
>
> On 2022-07-15 13:55:32 +0900, Kyotaro Horiguchi wrote:
> > Yeah, the limitation by max_sync_workers_per_subscription is performed
> > on subscriber, but replication slot drops happen not on the
> > subscriber, but at the termination of corresponding walsender process
> > on publisher.

We do drop the replication slots on subscribers since commit
ce0fdbfe97 once the initial sync is complete.

> > So, there's a lag between the finish of subscription
> > worker and the corresponding slot's drop.  Thus, a new sync worker can
> > be created while the walsenders corresponding to some already finished
> > sync workers is still going to finish.
>
> Why are we relying on the slots being dropped at the end of connection? That
> doesn't seem like a good idea to me. Can't we just do that explicitly?
>

We do that explicitly once the initial sync in finished.

-- 
With Regards,
Amit Kapila.