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

On Mon, Mar 25, 2024 at 5:10 PM Amit Kapila <amit.kapila16@gmail.com> wrote:
>
> I think we should keep pg_alter_replication_slot() as the last
> priority among the remaining patches for this release. Let's try to
> first finish the primary functionality of inactive_timeout patch.
> Otherwise, I agree that the problem reported by you should be fixed.

Noted. Will focus on v18-002 patch now.

I was debugging the flow and just noticed that RecoveryInProgress()
always returns 'true' during
StartupReplicationSlots()-->RestoreSlotFromDisk() (even on primary) as
'xlogctl->SharedRecoveryState' is always 'RECOVERY_STATE_CRASH' at
that time. The 'xlogctl->SharedRecoveryState' is changed  to
'RECOVERY_STATE_DONE' on primary and to 'RECOVERY_STATE_ARCHIVE' on
standby at a later stage in StartupXLOG() (after we are done loading
slots).

The impact of this is, the condition in RestoreSlotFromDisk() in v20-001:

if (!(RecoveryInProgress() && slot->data.synced))
     slot->last_inactive_time = GetCurrentTimestamp();

is merely equivalent to:

if (!slot->data.synced)
    slot->last_inactive_time = GetCurrentTimestamp();

Thus on primary, after restart, last_inactive_at is set correctly,
while on promoted standby (new primary), last_inactive_at is always
NULL after restart for the synced slots.

thanks
Shveta