Horton

Re: Synchronizing slots from primary to standby

Peter Smith <smithpb2250@gmail.com>

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From: Peter Smith <smithpb2250@gmail.com>
To: Amit Kapila <amit.kapila16@gmail.com>
Cc: shveta malik <shveta.malik@gmail.com>, Bertrand Drouvot <bertranddrouvot.pg@gmail.com>, "Zhijie Hou (Fujitsu)" <houzj.fnst@fujitsu.com>, Masahiko Sawada <sawada.mshk@gmail.com>, Ajin Cherian <itsajin@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: 2024-02-28T23:43:07Z
Lists: pgsql-hackers 
On Wed, Feb 28, 2024 at 10:21 PM Amit Kapila <amit.kapila16@gmail.com> wrote:
>
> On Wed, Feb 28, 2024 at 3:26 PM shveta malik <shveta.malik@gmail.com> wrote:
> >
> >
> > Here is the patch which addresses the above comments. Also optimized
> > the test a little bit. Now we use pg_sync_replication_slots() function
> > instead of worker to test the operator-redirection using search-patch.
> > This has been done to simplify the test case and reduce the added
> > time.
> >
>
> I have slightly adjusted the comments in the attached, otherwise, LGTM.
>
> --

- if (logical)
+ /*
+ * Set always-secure search path for the cases where the connection is
+ * used to run SQL queries, so malicious users can't get control.
+ */
+ if (logical || !replication)
  {
  PGresult   *res;

I found this condition a bit confusing. According to the
libpqrcv_connect function comment:

 * This function can be used for both replication and regular connections.
 * If it is a replication connection, it could be either logical or physical
 * based on input argument 'logical'.

IIUC that comment is saying the 'replication' flag is like the main
categorization and the 'logical' flag is like a subcategory (for when
'replication' is true). Therefore, won't the modified check be better
to be written the other way around? This will also be consistent with
the way the Assert was written.

SUGGESTION
if (!replication || logical)
{
  ...

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

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).