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

On Thu, Apr 4, 2024 at 1:32 PM Masahiko Sawada <sawada(dot)mshk(at)gmail(dot)com> wrote:
>
> 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.
>

Do you want to review the v34_0001* further or shall I proceed with
the commit of the same?

--
With Regards,
Amit Kapila.