Horton

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

Amit Kapila <amit.kapila16@gmail.com>

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From: Amit Kapila <amit.kapila16@gmail.com>
To: Bertrand Drouvot <bertranddrouvot.pg@gmail.com>
Cc: Bharath Rupireddy <bharath.rupireddyforpostgres@gmail.com>, shveta malik <shveta.malik@gmail.com>, Nathan Bossart <nathandbossart@gmail.com>, PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>
Date: 2024-03-20T02:28:20Z
Lists: pgsql-hackers

Commits

Same data as JSON: GET /api/v1/messages/:b64id/commits the thread's linked commits as JSON, with link sources. API reference →

  1. Add a test for commit ac0e33136a using the injection point.

  2. Invalidate inactive replication slots.

  3. Fix incorrect slot type in BuildTupleHashTableExt

  4. Allow synced slots to have their inactive_since.

  5. Change last_inactive_time to inactive_since in pg_replication_slots.

  6. Track last_inactive_time in pg_replication_slots.

  7. Track invalidation_reason in pg_replication_slots.

  8. Add option force_initdb to PostgreSQL::Test::Cluster:init()

  9. Add a failover option to subscriptions.

  10. Allow setting failover property in the replication command.

  11. Allow to enable failover property for replication slots via SQL API.

  12. Track conflict_reason in pg_replication_slots.

  13. Log messages for replication slot acquisition and release.

  14. Remove vacuum_defer_cleanup_age

  15. Fix corruption due to vacuum_defer_cleanup_age underflowing 64bit xids

  16. meson: Add initial version of meson based build system

On Tue, Mar 19, 2024 at 6:12 PM Bertrand Drouvot
<bertranddrouvot.pg@gmail.com> wrote:
>
> On Tue, Mar 19, 2024 at 04:20:35PM +0530, Amit Kapila wrote:
> > On Tue, Mar 19, 2024 at 3:11 PM Bertrand Drouvot
> > <bertranddrouvot.pg@gmail.com> wrote:
> > >
> > > On Tue, Mar 19, 2024 at 10:56:25AM +0530, Amit Kapila wrote:
> > > > On Mon, Mar 18, 2024 at 8:19 PM Bertrand Drouvot
> > > > <bertranddrouvot.pg@gmail.com> wrote:
> > > > > 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).
> > > > >
> > > >
> > > > Trying to invalidate at those two places makes sense to me but we
> > > > still need to cover the cases where it takes very long to resume the
> > > > slot activity and the dangling slot cases where the activity is never
> > > > resumed.
> > >
> > > I understand it's better to have the slot reflecting its real status internally
> > > but it is a real issue if that's not the case until the activity on it is resumed?
> > > (just asking, not saying we should not)
> > >
> >
> > Sorry, I didn't understand your point. Can you try to explain by example?
>
> Sorry if that was not clear, let me try to rephrase it first: what issue to you
> see if the invalidation of such a slot occurs only when its usage resume or
> when pg_get_replication_slots() is triggered? I understand that this could lead
> to the slot not being invalidated (maybe forever) but is that an issue for an
> inactive slot?
>

It has the risk of preventing WAL and row removal. I think this is the
primary reason we are at the first place planning to have such a
parameter. So, we should have some way to invalidate it even when the
walsender/backend process doesn't use it again.

-- 
With Regards,
Amit Kapila.