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

On Thu, Mar 14, 2024 at 7:58 PM Bharath Rupireddy
<bharath(dot)rupireddyforpostgres(at)gmail(dot)com> wrote:
>
> On Thu, Mar 14, 2024 at 12:24 PM Amit Kapila <amit(dot)kapila16(at)gmail(dot)com> wrote:
> >
> > On Wed, Mar 13, 2024 at 9:24 PM Bharath Rupireddy
> > >
> > > Yes, there will be some sort of duplicity if we emit conflict_reason
> > > as a text field. However, I still think the better way is to turn
> > > conflict_reason text to conflict boolean and set it to true only on
> > > rows_removed and wal_level_insufficient invalidations. When conflict
> > > boolean is true, one (including all the tests that we've added
> > > recently) can look for invalidation_reason text field for the reason.
> > > This sounds reasonable to me as opposed to we just mentioning in the
> > > docs that "if invalidation_reason is rows_removed or
> > > wal_level_insufficient it's the reason for conflict with recovery".

+1 on maintaining both conflicting and invalidation_reason

> > Fair point. I think we can go either way. Bertrand, Nathan, and
> > others, do you have an opinion on this matter?
>
> While we wait to hear from others on this, I'm attaching the v9 patch
> set implementing the above idea (check 0001 patch). Please have a
> look. I'll come back to the other review comments soon.

Thanks for the patch. JFYI, patch09 does not apply to HEAD, some
recent commit caused the conflict.

Some trivial comments on patch001 (yet to review other patches)

1)
info.c:

- "%s as caught_up, conflict_reason IS NOT NULL as invalid "
+ "%s as caught_up, invalidation_reason IS NOT NULL as invalid "

Can we revert back to 'conflicting as invalid' since it is a query for
logical slots only.

2)
040_standby_failover_slots_sync.pl:

- q{SELECT conflict_reason IS NULL AND synced AND NOT temporary FROM
pg_replication_slots WHERE slot_name = 'lsub1_slot';}
+ q{SELECT invalidation_reason IS NULL AND synced AND NOT temporary
FROM pg_replication_slots WHERE slot_name = 'lsub1_slot';}

Here too, can we have 'NOT conflicting' instead of '
invalidation_reason IS NULL' as it is a logical slot test.

thanks
Shveta