Re: Exit walsender before confirming remote flush in logical replication

On Wed, Dec 28, 2022 at 8:19 AM Hayato Kuroda (Fujitsu)
<kuroda(dot)hayato(at)fujitsu(dot)com> wrote:
>
> > In logical replication, it can happen today as well without
> > time-delayed replication. Basically, say apply worker is waiting to
> > acquire some lock that is already acquired by some backend then it
> > will have the same behavior. I have not verified this, so you may want
> > to check it once.
>
> Right, I could reproduce the scenario with following steps.
>
> 1. Construct pub -> sub logical replication system with streaming = off.
> 2. Define a table on both nodes.
>
> ```
> CREATE TABLE tbl (id int PRIMARY KEY);
> ```
>
> 3. Execute concurrent transactions.
>
> Tx-1 (on subscriber)
> BEGIN;
> INSERT INTO tbl SELECT i FROM generate_series(1, 5000) s(i);
>
> Tx-2 (on publisher)
> INSERT INTO tbl SELECT i FROM generate_series(1, 5000) s(i);
>
> 4. Try to shutdown publisher but it will be failed.
>
> ```
> $ pg_ctl stop -D publisher
> waiting for server to shut down............................................................... failed
> pg_ctl: server does not shut down
> ```

Thanks for the verification. BTW, do you think we should document this
either with time-delayed replication or otherwise unless this is
already documented?

Another thing we can investigate here why do we need to ensure that
there is no pending send before shutdown.

--
With Regards,
Amit Kapila.