Horton

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

Bertrand Drouvot <bertranddrouvot.pg@gmail.com>

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From: Bertrand Drouvot <bertranddrouvot.pg@gmail.com>
To: Amit Kapila <amit.kapila16@gmail.com>
Cc: Bharath Rupireddy <bharath.rupireddyforpostgres@gmail.com>, Nathan Bossart <nathandbossart@gmail.com>, PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>
Date: 2024-03-22T12:00:07Z
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

Hi,

On Fri, Mar 22, 2024 at 03:56:23PM +0530, Amit Kapila wrote:
> On Fri, Mar 22, 2024 at 3:15 PM Bertrand Drouvot
> <bertranddrouvot.pg@gmail.com> wrote:
> >
> > On Fri, Mar 22, 2024 at 01:45:01PM +0530, Bharath Rupireddy wrote:
> >
> > 1 ===
> >
> > @@ -691,6 +699,13 @@ ReplicationSlotRelease(void)
> >                 ConditionVariableBroadcast(&slot->active_cv);
> >         }
> >
> > +       if (slot->data.persistency == RS_PERSISTENT)
> > +       {
> > +               SpinLockAcquire(&slot->mutex);
> > +               slot->last_inactive_at = GetCurrentTimestamp();
> > +               SpinLockRelease(&slot->mutex);
> > +       }
> >
> > I'm not sure we should do system calls while we're holding a spinlock.
> > Assign a variable before?
> >
> > 2 ===
> >
> > Also, what about moving this here?
> >
> > "
> >     if (slot->data.persistency == RS_PERSISTENT)
> >     {
> >         /*
> >          * Mark persistent slot inactive.  We're not freeing it, just
> >          * disconnecting, but wake up others that may be waiting for it.
> >          */
> >         SpinLockAcquire(&slot->mutex);
> >         slot->active_pid = 0;
> >         SpinLockRelease(&slot->mutex);
> >         ConditionVariableBroadcast(&slot->active_cv);
> >     }
> > "
> >
> > That would avoid testing twice "slot->data.persistency == RS_PERSISTENT".
> >
> 
> That sounds like a good idea. Also, don't we need to consider physical
> slots where we don't reserve WAL during slot creation? I don't think
> there is a need to set inactive_at for such slots.

If the slot is not active, why shouldn't we set inactive_at? I can understand
that such a slots do not present "any risks" but I think we should still set
inactive_at (also to not give the false impression that the slot is active).

> > 5 ===
> >
> > Most of the fields that reflect a time (not duration) in the system views are
> > xxxx_time, so I'm wondering if instead of "last_inactive_at" we should use
> > something like "last_inactive_time"?
> >
> 
> How about naming it as last_active_time? This will indicate the time
> at which the slot was last active.

I thought about it too but I think it could be missleading as one could think that 
it should be updated each time WAL record decoding is happening.

Regards,

-- 
Bertrand Drouvot
PostgreSQL Contributors Team
RDS Open Source Databases
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