Re: [Patch] ALTER SYSTEM READ ONLY

On Thu, Jul 23, 2020 at 3:57 AM Amul Sul <sulamul(at)gmail(dot)com> wrote:

> Well, once we've initiated the change to a read-only state, we probably want to
> always either finish that change or go back to read-write, even if the process
> that initiated the change is interrupted. Leaving the system in a
> half-way-in-between state long term seems bad. Maybe we would have put some
> background process, but choose the checkpointer in charge of making the state
> change and to avoid the new background process to keep the first version patch
> simple. The checkpointer isn't likely to get killed, but if it does, it will
> be relaunched and the new one can clean things up. On the other hand, I agree
> making the checkpointer responsible for more than one thing might not
> be a good idea
> but I don't think the postmaster should do the work that any
> background process can
> do.

+1 for doing it in a background process rather than in the backend
itself (as we can't risk doing it in a backend as it can crash and won't
restart and clean up as a background process would).

As my co-worker pointed out to me, doing the work in the postmaster is a
very bad idea as we don't want delays in serving connection requests on
account of the barrier that comes with this patch.

I would like to see this responsibility in a separate auxiliary process
but I guess having it in the checkpointer isn't the end of the world.

Regards,
Soumyadeep (VMware)