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

Hi,

On Thu, Mar 14, 2024 at 12:27:26PM +0530, Amit Kapila wrote:
> On Wed, Mar 13, 2024 at 10:16 PM Bharath Rupireddy
> <bharath(dot)rupireddyforpostgres(at)gmail(dot)com> wrote:
> >
> > On Wed, Mar 13, 2024 at 11:13 AM shveta malik <shveta(dot)malik(at)gmail(dot)com> wrote:
> > >
> > > > Thanks. v8-0001 is how it looks. Please see the v8 patch set with this change.
> > >
> > > JFYI, the patch does not apply to the head. There is a conflict in
> > > multiple files.
> >
> > Thanks for looking into this. I noticed that the v8 patches needed
> > rebase. Before I go do anything with the patches, I'm trying to gain
> > consensus on the design. Following is the summary of design choices
> > we've discussed so far:
> > 1) conflict_reason vs invalidation_reason.
> > 2) When to compute the XID age?
> >
>
> I feel we should focus on two things (a) one is to introduce a new
> column invalidation_reason, and (b) let's try to first complete
> invalidation due to timeout. We can look into XID stuff if time
> permits, remember, we don't have ample time left.

Agree. While it makes sense to invalidate slots for wal removal in
CreateCheckPoint() (because this is the place where wal is removed), I 'm not
sure this is the right place for the 2 new cases.

Let's focus on the timeout one as proposed above (as probably the simplest one):
as this one is purely related to time and activity what about to invalidate them
when?:

- their usage resume
- in pg_get_replication_slots()

The idea is to invalidate the slot when one resumes activity on it or wants to
get information about it (and among other things wants to know if the slot is
valid or not).

Thoughts?

Regards,

--
Bertrand Drouvot
PostgreSQL Contributors Team
RDS Open Source Databases
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