Re: Introduce XID age and inactive timeout based replication slot invalidation

Hi,

On Sun, Mar 31, 2024 at 10:25:46AM +0530, Bharath Rupireddy wrote:
> On Thu, Mar 28, 2024 at 3:13 PM Bertrand Drouvot
> <bertranddrouvot(dot)pg(at)gmail(dot)com> wrote:
> > I think in this case it should always reflect the value from the primary (so
> > that one can understand why it is invalidated).
>
> I'll come back to this as soon as we all agree on inactive_since
> behavior for synced slots.

Makes sense. Also if the majority of us thinks it's not needed for inactive_since
to be an exact copy of the primary, then let's go that way.

> > I think when it is invalidated it should always reflect the value from the
> > primary (so that one can understand why it is invalidated).
>
> I'll come back to this as soon as we all agree on inactive_since
> behavior for synced slots.

Yeah.

> > T4 ===
> >
> > Also, it looks like querying pg_replication_slots() does not trigger an
> > invalidation: I think it should if the slot is not invalidated yet (and matches
> > the invalidation criteria).
>
> There's a different opinion on this, check comment #3 from
> https://www.postgresql.org/message-id/CAA4eK1LLj%2BeaMN-K8oeOjfG%2BUuzTY%3DL5PXbcMJURZbFm%2B_aJSA%40mail.gmail.com.

Oh right, I can see Amit's point too. Let's put pg_replication_slots() out of
the game then.

> > CR6 ===
> >
> > +static bool
> > +InvalidateSlotForInactiveTimeout(ReplicationSlot *slot, bool need_locks)
> > +{
> >
> > InvalidatePossiblyInactiveSlot() maybe?
>
> I think we will lose the essence i.e. timeout from the suggested
> function name, otherwise just the inactive doesn't give a clearer
> meaning. I kept it that way unless anyone suggests otherwise.

Right. OTOH I think that "Possibly" adds some nuance (like InvalidatePossiblyObsoleteSlot()
is already doing).

> Please see the attached v30 patch. 0002 is where all of the above
> review comments have been addressed.

Thanks! FYI, I did not look at the content yet, just replied to the above
comments.

Regards,

--
Bertrand Drouvot
PostgreSQL Contributors Team
RDS Open Source Databases
Amazon Web Services: https://aws.amazon.com