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

On Tue, 10 Dec 2024 at 17:21, Nisha Moond <nisha(dot)moond412(at)gmail(dot)com> wrote:
>
> On Fri, Dec 6, 2024 at 11:04 AM vignesh C <vignesh21(at)gmail(dot)com> wrote:
> >
> >
> > Determining the correct time may be challenging for users, as it
> > depends on when the active_since value is set, as well as when the
> > checkpoint_timeout occurs and the subsequent checkpoint is triggered.
> > Even if the user sets it to an appropriate value, there is still a
> > possibility of delayed identification due to the timing of when the
> > slot's active_timeout is being set. Including this information in the
> > documentation should be sufficient.
> >
>
> +1
> v54 documents this information as suggested.
>
> Attached the v54 patch-set addressing all the comments till now in

Few comments on the test added:
1) Can we remove this and set idle_replication_slot_timeout while the
standby node is created itself during append_conf:
+# Set timeout GUC on the standby to verify that the next checkpoint will not
+# invalidate synced slots.
+my $idle_timeout_1s = 1;
+$standby1->safe_psql(
+ 'postgres', qq[
+ ALTER SYSTEM SET idle_replication_slot_timeout TO '${idle_timeout_1s}s';
+]);
+$standby1->reload;

2) You can move these statements before the standby node is created:
+# Create sync slot on the primary
+$primary->psql('postgres',
+ q{SELECT pg_create_logical_replication_slot('sync_slot1',
'test_decoding', false, false, true);}
+);
+
+# Create standby slot on the primary
+$primary->safe_psql(
+ 'postgres', qq[
+ SELECT pg_create_physical_replication_slot(slot_name :=
'sb_slot1', immediately_reserve := true);
+]);

3) Do we need autovacuum as off for these tests, is there any
probability of a test failure without this. I felt it should not
impact these tests, if not we can remove this:
+# Avoid unpredictability
+$primary->append_conf(
+ 'postgresql.conf', qq{
+checkpoint_timeout = 1h
+autovacuum = off
+});

4) Generally we mention single char in single quotes, we can update "t" to 't':
+ ),
+ "t",
+ 'logical slot sync_slot1 is synced to standby');
+

5) Similarly here too:
+ WHERE slot_name = 'sync_slot1'
+ AND invalidation_reason IS NULL;}
+ ),
+ "t",
+ 'check that synced slot sync_slot1 has not been invalidated on
standby');

6) This standby offset is not used anywhere, it can be removed:
+my $logstart = -s $standby1->logfile;
+
+# Set timeout GUC on the standby to verify that the next checkpoint will not
+# invalidate synced slots.

Regards,
Vignesh