Horton

Re: Synchronizing slots from primary to standby

Amit Kapila <amit.kapila16@gmail.com>

View thread View on postgr.es
From: Amit Kapila <amit.kapila16@gmail.com>
To: Peter Smith <smithpb2250@gmail.com>
Cc: shveta malik <shveta.malik@gmail.com>, Ajin Cherian <itsajin@gmail.com>, "Zhijie Hou (Fujitsu)" <houzj.fnst@fujitsu.com>, Masahiko Sawada <sawada.mshk@gmail.com>, Bertrand Drouvot <bertranddrouvot.pg@gmail.com>, Dilip Kumar <dilipbalaut@gmail.com>, Nisha Moond <nisha.moond412@gmail.com>, "Hayato Kuroda (Fujitsu)" <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: 2024-02-07T10:59:07Z
Lists: pgsql-hackers 
On Tue, Feb 6, 2024 at 12:08 PM Peter Smith <smithpb2250@gmail.com> wrote:
>
> There seems some muddling of names here:
> - "local" versus ? and "remote" versus "primary"; or sometimes the
> function does not give an indication.
> - "sync_slot" versus "synced_slot" versus nothing
> - "check" versus "validate"
> - etc.
>
> Below are some suggestions (some are unchanged); probably there are
> better ideas for names but my point is that the current names could be
> improved:
>
> CURRENT                                 SUGGESTION
...
> drop_obsolete_slots                  drop_local_synced_slots

The new name doesn't convey the intent of the function. If we want to
have a difference based on remote/local slots then we can probably
name it as drop_local_obsolete_slots.

> reserve_wal_for_slot                 reserve_wal_for_local_slot
> local_slot_update                      update_local_synced_slot
> update_and_persist_slot           update_and_persist_local_synced_slot
>

The new names sound better in the above cases as the current names
appear too generic.

> get_slot_invalidation_cause      get_slot_conflict_reason
> synchronize_slots                      synchronize_remote_slots_to_local
> synchronize_one_slot                synchronize_remote_slot_to_local
>

The new names don't sound like an improvement.

> validate_primary_slot                check_remote_synced_slot_exists
> validate_slotsync_params         check_local_config
>

In the above cases, the current name conveys the intent of function
whereas new names sound a bit generic. So, let's not change in this
case.

-- 
With Regards,
Amit Kapila.

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).