Horton

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

shveta malik <shveta.malik@gmail.com>

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From: shveta malik <shveta.malik@gmail.com>
To: Bharath Rupireddy <bharath.rupireddyforpostgres@gmail.com>
Cc: Peter Smith <smithpb2250@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>, shveta malik <shveta.malik@gmail.com>
Date: 2024-09-04T09:18:51Z
Lists: pgsql-hackers

Commits

Same data as JSON: GET /api/v1/messages/:b64id/commits the thread's linked commits as JSON, with link sources. API reference →

  1. Add a test for commit ac0e33136a using the injection point.

  2. Invalidate inactive replication slots.

  3. Fix incorrect slot type in BuildTupleHashTableExt

  4. Allow synced slots to have their inactive_since.

  5. Change last_inactive_time to inactive_since in pg_replication_slots.

  6. Track last_inactive_time in pg_replication_slots.

  7. Track invalidation_reason in pg_replication_slots.

  8. Add option force_initdb to PostgreSQL::Test::Cluster:init()

  9. Add a failover option to subscriptions.

  10. Allow setting failover property in the replication command.

  11. Allow to enable failover property for replication slots via SQL API.

  12. Track conflict_reason in pg_replication_slots.

  13. Log messages for replication slot acquisition and release.

  14. Remove vacuum_defer_cleanup_age

  15. Fix corruption due to vacuum_defer_cleanup_age underflowing 64bit xids

  16. meson: Add initial version of meson based build system

On Wed, Sep 4, 2024 at 9:17 AM shveta malik <shveta.malik@gmail.com> wrote:
>
> On Tue, Sep 3, 2024 at 3:01 PM shveta malik <shveta.malik@gmail.com> wrote:
> >
> >


1)
It is related to one of my previous comments (pt 3 in [1]) where I
stated that inactive_since should not keep on changing once a slot is
invalidated.
Below is one side effect if inactive_since keeps on changing:

postgres=# SELECT * FROM pg_replication_slot_advance('mysubnew1_1',
pg_current_wal_lsn());
ERROR:  can no longer get changes from replication slot "mysubnew1_1"
DETAIL:  The slot became invalid because it was inactive since
2024-09-04 10:03:56.68053+05:30, which is more than 10 seconds ago.
HINT:  You might need to increase "replication_slot_inactive_timeout.".

postgres=# select now();
               now
---------------------------------
 2024-09-04 10:04:00.26564+05:30

'DETAIL' gives wrong information, we are not past 10-seconds. This is
because inactive_since got updated even in ERROR scenario.


2)
One more issue in this message is, once I set
replication_slot_inactive_timeout to a bigger value, it becomes more
misleading. This is because invalidation was done in the past using
previous value while message starts showing new value:

ALTER SYSTEM SET replication_slot_inactive_timeout TO '36h';

--see 129600 secs in DETAIL and the current time.
postgres=# SELECT * FROM pg_replication_slot_advance('mysubnew1_1',
pg_current_wal_lsn());
ERROR:  can no longer get changes from replication slot "mysubnew1_1"
DETAIL:  The slot became invalid because it was inactive since
2024-09-04 10:06:38.980939+05:30, which is more than 129600 seconds
ago.
postgres=# select now();
               now
----------------------------------
 2024-09-04 10:07:35.201894+05:30

I feel we should change this message itself.

~~~~~

When invalidation is due to wal_removed, we get a way simpler message:

newdb1=# SELECT * FROM pg_replication_slot_advance('mysubnew1_2',
pg_current_wal_lsn());
ERROR:  replication slot "mysubnew1_2" cannot be advanced
DETAIL:  This slot has never previously reserved WAL, or it has been
invalidated.

This message does not mention 'max_slot_wal_keep_size'. We should have
a similar message for our case. Thoughts?

[1]:  https://www.postgresql.org/message-id/CAJpy0uC8Dg-0JS3NRUwVUemgz5Ar2v3_EQQFXyAigWSEQ8U47Q%40mail.gmail.com

thanks
Shveta