Re: Restrict copying of invalidated replication slots

On Thu, Feb 27, 2025 at 10:47 AM Masahiko Sawada <sawada(dot)mshk(at)gmail(dot)com> wrote:
>
> On Tue, Feb 25, 2025 at 7:33 PM Amit Kapila <amit(dot)kapila16(at)gmail(dot)com> wrote:
> >
> > AFAICU, InvalidateObsoleteReplicationSlots() is not serialized with
> > this operation. So, isn't it possible that the source slot exists at
> > the later position in ReplicationSlotCtl->replication_slots and the
> > loop traversing slots is already ahead from the point where the newly
> > copied slot is created?
>
> Good point. I think it's possible.
>
> > If so, the newly created slot won't be marked
> > as invalid whereas the source slot will be marked as invalid. I agree
> > that even in such a case, at a later point, the newly created slot
> > will also be marked as invalid.
>
> The wal_status of the newly created slot would immediately become
> 'lost' and the next checkpoint will invalidate it. Do we need to do
> something to deal with this case?
>

+ /* Check if source slot became invalidated during the copy operation */
+ if (second_slot_contents.data.invalidated != RS_INVAL_NONE)
+ ereport(ERROR,
+ errmsg("cannot copy replication slot \"%s\"",
+ NameStr(*src_name)),
+ errdetail("The source replication slot was invalidated during the
copy operation."));

How about adding a similar test as above for MyReplicationSlot? That
should suffice the need because we have already acquired the new slot
by this time and invalidation should signal this process before
marking the new slot as invalid.

--
With Regards,
Amit Kapila.