Re: Exit walsender before confirming remote flush in logical replication

On Fri, Feb 3, 2023 at 5:38 PM Hayato Kuroda (Fujitsu)
<kuroda(dot)hayato(at)fujitsu(dot)com> wrote:
>
> Dear Amit, Sawada-san,
>
> > > IIUC there is no difference between smart shutdown and fast shutdown
> > > in logical replication walsender, but reading the doc[1], it seems to
> > > me that in the smart shutdown mode, the server stops existing sessions
> > > normally. For example, If the client is psql that gets stuck for some
> > > reason and the network buffer gets full, the smart shutdown waits for
> > > a backend process to send all results to the client. I think the
> > > logical replication walsender should follow this behavior for
> > > consistency. One idea is to distinguish smart shutdown and fast
> > > shutdown also in logical replication walsender so that we disconnect
> > > even without the done message in fast shutdown mode, but I'm not sure
> > > it's worthwhile.
> > >
> >
> > The main problem we want to solve here is to avoid shutdown failing in
> > case walreceiver/applyworker is busy waiting for some lock or for some
> > other reason as shown in the email [1].
> >

For this problem isn't using -t (timeout) avoid it? So, if there is a
pending WAL, users can always use -t option to allow the shutdown to
complete. Now, I agree that it is not very clear how much time to
specify but a user has some option to allow the shutdown to complete.
I am not telling that teaching walsenders about shutdown modes is
completely a bad idea but it doesn't seem necessary to allow shutdowns
to complete.

--
With Regards,
Amit Kapila.