Re: [PoC] pg_upgrade: allow to upgrade publisher node

On Mon, Aug 7, 2023 at 3:46 PM Amit Kapila <amit(dot)kapila16(at)gmail(dot)com> wrote:
>
> On Mon, Aug 7, 2023 at 1:06 PM Julien Rouhaud <rjuju123(at)gmail(dot)com> wrote:
> >
> > On Mon, Aug 07, 2023 at 12:42:33PM +0530, Amit Kapila wrote:
> > > On Mon, Aug 7, 2023 at 11:29 AM Julien Rouhaud <rjuju123(at)gmail(dot)com> wrote:
> > > >
> > > > Unless I'm missing something I don't see what prevents something to connect
> > > > using the replication protocol and issue any query or even create new
> > > > replication slots?
> > > >
> > >
> > > I think the point is that if we have any slots where we have not
> > > consumed the pending WAL (other than the expected like
> > > SHUTDOWN_CHECKPOINT) or if there are invalid slots then the upgrade
> > > won't proceed and we will request user to remove such slots or ensure
> > > that WAL is consumed by slots. So, I think in the case you mentioned,
> > > the upgrade won't succeed.
> >
> > What if new slots are added while the old instance is started in the middle of
> > pg_upgrade, *after* the various checks are done?
> >
>
> They won't be copied but I think that won't be any different than
> other objects like tables. Anyway, I have another idea which is to not
> allow creating slots during binary upgrade unless one specifically
> requests it by having an API like binary_upgrade_allow_slot_create()
> similar to existing APIs binary_upgrade_*.
>

Sawada-San, Julien, and others, do you have any thoughts on the above point?

--
With Regards,
Amit Kapila.