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

vignesh C <vignesh21@gmail.com>

From: vignesh C <vignesh21@gmail.com>

To: Nisha Moond <nisha.moond412@gmail.com>

Cc: Peter Smith <smithpb2250@gmail.com>, "Hayato Kuroda (Fujitsu)" <kuroda.hayato@fujitsu.com>, shveta malik <shveta.malik@gmail.com>, Bharath Rupireddy <bharath.rupireddyforpostgres@gmail.com>, Amit Kapila <amit.kapila16@gmail.com>, Ajin Cherian <itsajin@gmail.com>, Bertrand Drouvot <bertranddrouvot.pg@gmail.com>, Masahiko Sawada <sawada.mshk@gmail.com>, Nathan Bossart <nathandbossart@gmail.com>, PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>

Date: 2024-12-11T06:51:11Z

Lists: pgsql-hackers

Commits

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Add a test for commit ac0e33136a using the injection point.
- 8a695d7998be 18.0 landed
Invalidate inactive replication slots.
- ac0e33136abc 18.0 landed
Fix incorrect slot type in BuildTupleHashTableExt
- d96d1d5152f3 18.0 cited
Allow synced slots to have their inactive_since.
- 6f132ed693b6 17.0 landed
Change last_inactive_time to inactive_since in pg_replication_slots.
- 6d49c8d4b4f4 17.0 landed
Track last_inactive_time in pg_replication_slots.
- a11f330b5584 17.0 landed
Track invalidation_reason in pg_replication_slots.
- 6ae701b4378d 17.0 landed
Add option force_initdb to PostgreSQL::Test::Cluster:init()
- ff9e1e764fcc 17.0 cited
Add a failover option to subscriptions.
- 776621a5e479 17.0 cited
Allow setting failover property in the replication command.
- 73292404370c 17.0 cited
Allow to enable failover property for replication slots via SQL API.
- c393308b69d2 17.0 cited
Track conflict_reason in pg_replication_slots.
- 007693f2a3ac 17.0 cited
Log messages for replication slot acquisition and release.
- 7c3fb505b14e 17.0 cited
Remove vacuum_defer_cleanup_age
- 1118cd37eb61 16.0 cited
Fix corruption due to vacuum_defer_cleanup_age underflowing 64bit xids
- be504a3e974d 16.0 cited
meson: Add initial version of meson based build system
- e6927270cd18 16.0 cited

On Tue, 10 Dec 2024 at 17:21, Nisha Moond <nisha.moond412@gmail.com> wrote:
>
> On Fri, Dec 6, 2024 at 11:04 AM vignesh C <vignesh21@gmail.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