Horton

Re: Synchronizing slots from primary to standby

Euler Taveira <euler@eulerto.com>

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From: "Euler Taveira" <euler@eulerto.com>
To: "houzj.fnst@fujitsu.com" <houzj.fnst@fujitsu.com>, "Amit Kapila" <amit.kapila16@gmail.com>, "shveta.malik@gmail.com" <shveta.malik@gmail.com>
Cc: "Peter Smith" <smithpb2250@gmail.com>, "Bertrand Drouvot" <bertranddrouvot.pg@gmail.com>, "Ajin Cherian" <itsajin@gmail.com>, "Masahiko Sawada" <sawada.mshk@gmail.com>, "Dilip Kumar" <dilipbalaut@gmail.com>, "Nisha Moond" <nisha.moond412@gmail.com>, "kuroda.hayato@fujitsu.com" <kuroda.hayato@fujitsu.com>, "Bharath Rupireddy" <bharath.rupireddyforpostgres@gmail.com>, "Peter Eisentraut" <peter.eisentraut@enterprisedb.com>, "Bruce Momjian" <bruce@momjian.us>, "Ashutosh Sharma" <ashu.coek88@gmail.com>, "Andres Freund" <andres@anarazel.de>, pgsql-hackers <pgsql-hackers@postgresql.org>, "Alvaro Herrera" <alvherre@alvh.no-ip.org>
Date: 2024-02-01T02:45:04Z
Lists: pgsql-hackers 
On Mon, Jan 29, 2024, at 10:17 AM, Zhijie Hou (Fujitsu) wrote:
> Attach the V72-0001 which addressed above comments, other patches will be
> rebased and posted after pushing first patch. Thanks Shveta for helping address
> the comments.

While working on another patch I noticed a new NOTICE message:

NOTICE:  changed the failover state of replication slot "foo" on publisher to false

I wasn't paying much attention to this thread then I start reading the 2
patches that was recently committed. The message above surprises me because
pg_createsubscriber starts to emit this message. The reason is that it doesn't
create the replication slot during the CREATE SUBSCRIPTION. Instead, it creates
the replication slot with failover = false and no such option is informed
during CREATE SUBSCRIPTION which means it uses the default value (failover =
false). I expect that I don't see any message because it is *not* changing the
behavior. I was wrong. It doesn't check the failover state on publisher, it
just executes walrcv_alter_slot() and emits a message.

IMO if we are changing an outstanding property on node A from node B, node B
already knows (or might know) about that behavior change (because it is sending
the command), however, node A doesn't (unless log_replication_commands = on --
it is not the default).

Do we really need this message as NOTICE? I would set it to DEBUG1 if it is
worth or even remove it (if we consider there are other ways to obtain the same
information).


--
Euler Taveira
EDB   https://www.enterprisedb.com/

Commits

  1. Doc: Add the new section "Logical Replication Failover".

  2. Fix the review comments and a bug in the slot sync code.

  3. Fix a test in failover slots regression test.

  4. Fix the intermittent buildfarm failures in 040_standby_failover_slots_sync.

  5. Split XLogCtl->LogwrtResult into separate struct members

  6. Ensure that the sync slots reach a consistent state after promotion without losing data.

  7. Introduce a new GUC 'standby_slot_names'.

  8. Fix BF failure introduced by commit b3f6b14cf4.

  9. Fixups for commit 93db6cbda0.

  10. Fix BF failure in commit 93db6cbda0.

  11. Add a new slot sync worker to synchronize logical slots.

  12. Improve ERROR/LOG messages added by commits ddd5f4f54a and 7a424ece48.

  13. Disable autovacuum on primary in 040_standby_failover_slots_sync test.

  14. Fix the incorrect format specifier used in commit 7a424ece48.

  15. Change the LOG level in 040_standby_failover_slots_sync.pl to DEBUG2.

  16. Add more LOG and DEBUG messages for slot synchronization.

  17. Another try to fix BF failure introduced in commit ddd5f4f54a.

  18. Fix BF introduced in commit ddd5f4f54a.

  19. Add a slot synchronization function.

  20. Clean-ups for 776621a5e4 and 7329240437.

  21. Enhance libpqrcv APIs to support slot synchronization.

  22. Add a failover option to subscriptions.

  23. Allow setting failover property in the replication command.

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

  25. Add macros for looping through a List without a ListCell.

  26. Track conflict_reason in pg_replication_slots.

  27. Allow upgrades to preserve the full subscription's state.

  28. Add support for incremental backup.

  29. Simplify some logic in CreateReplicationSlot()

  30. Fix uninitialized access to InitialRunningXacts during decoding after ERROR.

  31. Flexible options for CREATE_REPLICATION_SLOT.

  32. Empty search_path in logical replication apply worker and walsender.

  33. Fix oldest xmin and LSN computation across repslots after advancing

  34. Require C99 (and thus MSCV 2013 upwards).