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

On Thu, Apr 4, 2024 at 1:34 PM Bharath Rupireddy
<bharath(dot)rupireddyforpostgres(at)gmail(dot)com> wrote:
>
> On Thu, Apr 4, 2024 at 9:42 AM Masahiko Sawada <sawada(dot)mshk(at)gmail(dot)com> wrote:
> >
> > @@ -1368,6 +1416,7 @@ ShutDownSlotSync(void)
> > if (SlotSyncCtx->pid == InvalidPid)
> > {
> > SpinLockRelease(&SlotSyncCtx->mutex);
> > + update_synced_slots_inactive_since();
> > return;
> > }
> > SpinLockRelease(&SlotSyncCtx->mutex);
> > @@ -1400,6 +1449,8 @@ ShutDownSlotSync(void)
> > }
> >
> > SpinLockRelease(&SlotSyncCtx->mutex);
> > +
> > + update_synced_slots_inactive_since();
> > }
> >
> > Why do we want to update all synced slots' inactive_since values at
> > shutdown in spite of updating the value every time when releasing the
> > slot? It seems to contradict the fact that inactive_since is updated
> > when releasing or restoring the slot.
>
> It is to get the inactive_since right for the cases where the standby
> is promoted without a restart similar to when a standby is promoted
> with restart in which case the inactive_since is set to current time
> in RestoreSlotFromDisk.
>
> Imagine the slot is synced last time at time t1 and then a few hours
> passed, the standby is promoted without a restart. If we don't set
> inactive_since to current time in this case in ShutDownSlotSync, the
> inactive timeout invalidation mechanism can kick in immediately.
>

Thank you for the explanation! I understood the needs.

Regards,

--
Masahiko Sawada
Amazon Web Services: https://aws.amazon.com