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

Hi,

On Thu, Mar 21, 2024 at 04:13:31PM +0530, Bharath Rupireddy wrote:
> On Thu, Mar 21, 2024 at 3:20 PM Amit Kapila <amit.kapila16@gmail.com> wrote:
> >
> > > My concern was that we set catalog_xmin at logical slot creation time. So if we
> > > set last_inactive_at to zero at creation time and the slot is not used for a long
> > > period of time > timeout, then I think it's not helping there.
> >
> > But, we do call ReplicationSlotRelease() after slot creation. For
> > example, see CreateReplicationSlot(). So wouldn't that take care of
> > the case you are worried about?
> 
> Right. That's true even for pg_create_physical_replication_slot and
> pg_create_logical_replication_slot. AFAICS, setting it to the current
> timestamp in ReplicationSlotRelease suffices unless I'm missing
> something.

Right, but we have:

"
    if (set_last_inactive_at &&
        slot->data.persistency == RS_PERSISTENT)
    {
        /*
         * There's no point in allowing failover slots to get invalidated
         * based on slot's inactive_timeout parameter on standby. The failover
         * slots simply get synced from the primary on the standby.
         */
        if (!(RecoveryInProgress() && slot->data.failover))
        {
            SpinLockAcquire(&slot->mutex);
            slot->last_inactive_at = GetCurrentTimestamp();
            SpinLockRelease(&slot->mutex);
        }
    }
"

while we set set_last_inactive_at to false at creation time so that last_inactive_at
is not set to GetCurrentTimestamp(). We should set set_last_inactive_at to true
if a timeout is provided during the slot creation.

Regards,

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