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

Peter Smith <smithpb2250@gmail.com>

From: Peter Smith <smithpb2250@gmail.com>

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

Cc: Shlok Kyal <shlok.kyal.oss@gmail.com>, Amit Kapila <amit.kapila16@gmail.com>, vignesh C <vignesh21@gmail.com>, "Hayato Kuroda (Fujitsu)" <kuroda.hayato@fujitsu.com>, shveta malik <shveta.malik@gmail.com>, Bharath Rupireddy <bharath.rupireddyforpostgres@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: 2025-01-21T02:51:51Z

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

Some review comments for patch v61-0001.

======
src/backend/replication/slot.c

InvalidatePossiblyObsoleteSlot:

1.
  /*
  * Check if the slot needs to be invalidated. If it needs to be
- * invalidated, and is not currently acquired, acquire it and mark it
- * as having been invalidated.  We do this with the spinlock held to
- * avoid race conditions -- for example the restart_lsn could move
- * forward, or the slot could be dropped.
+ * invalidated, and is already ours, mark it as having been
+ * invalidated; otherwise, acquire it first and then mark it as having
+ * been invalidated. We do this with the spinlock held to avoid race
+ * conditions -- for example the restart_lsn could move forward, or
+ * the slot could be dropped.
  */

Can't you just word this as "mark it as invalidated" (which you do
later anyway) instead of "mark is as having been invalidated"?  (this
is in two places).

~~~

2.
+ /*
+ * The logical replication slots shouldn't be invalidated as GUC
+ * max_slot_wal_keep_size is set to -1 during the binary upgrade.
+ * See check_old_cluster_for_valid_slots() where we ensure that no
+ * invalidated before the upgrade.
+ */
+ Assert(!(*invalidated && SlotIsLogical(s) && IsBinaryUpgrade));

2a.
I know this sentence was the same before you moved it, but "ensure
that no invalidated" seems like there are some words missing.

2b.
TBH, I this part confused me (the code is repeated in a couple of
places). AFAICT the code/comment does not match quite right. The
comment refers to a setting that is "during binary upgrade", yet the
Assert can only pass if IsBinaryUpgrade is false. (??)

I'm unsure of the intent; perhaps it should be like:

if (IsBinaryUpgrade)
Assert(!(*invalidated && SlotIsLogical(s)));

======
Kind Regards,
Peter Smith.
Fujitsu Australia