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: "Zhijie Hou (Fujitsu)" <houzj.fnst@fujitsu.com>, Amit Kapila <amit.kapila16@gmail.com>, Nathan Bossart <nathandbossart@gmail.com>, Álvaro Herrera <alvherre@alvh.no-ip.org>, vignesh C <vignesh21@gmail.com>, Shlok Kyal <shlok.kyal.oss@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>, PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>

Date: 2025-02-16T22:18:28Z

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 v78-0001.

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

ReportSlotInvalidation:

1.
+ int minutes;
+ int secs;

The variables 'minutes' and 'seconds' are only used by case
RS_INVAL_IDLE_TIMEOUT, so I think it would be better to make a new
code block for that case where you can declare and initialise these in
one go at that scope.

~~~

DetermineSlotInvalidationCause:

2.
+ if (SlotIsLogical(s) &&
+ /* invalid DB oid signals a shared relation */
+ (dboid == InvalidOid || dboid == s->data.database))
+ {

The comment placement in the master code was ok because then there
were different statements, but now in this patch multiple conditions
are combined, and this comment seems strangely placed.

~~~

GetSlotInvalidationCause:

3.
I understand your argument "let's not change anything unless
absolutely necessary for our patch", but in this case since half the
function is changing anyway it seems a missed opportunity to not
simplify the rest of the code "in passing" to make it consistent with
the newly added partner function GetSlotInvalidationCauseName. My
question is "if not now, then when?", because I expect a future patch
to do this might be rejected as being too trivial, so by not changing
now probably these functions are doomed to be inconsistent forever.
Anyway it is just my opinion -- leave it as-is if you wish.

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