Horton

Re: Synchronizing slots from primary to standby

Peter Smith <smithpb2250@gmail.com>

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From: Peter Smith <smithpb2250@gmail.com>
To: "Zhijie Hou (Fujitsu)" <houzj.fnst@fujitsu.com>
Cc: Amit Kapila <amit.kapila16@gmail.com>, shveta malik <shveta.malik@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>, "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: 2024-01-30T01:59:04Z
Lists: pgsql-hackers 
Here are some review comments for v72-0001

======
doc/src/sgml/ref/alter_subscription.sgml

1.
+      parameter value of the subscription. Otherwise, the slot on the
+      publisher may behave differently from what subscription's
+      <link linkend="sql-createsubscription-params-with-failover"><literal>failover</literal></link>
+      option says. The slot on the publisher could either be
+      synced to the standbys even when the subscription's
+      <link linkend="sql-createsubscription-params-with-failover"><literal>failover</literal></link>
+      option is disabled or could be disabled for sync
+      even when the subscription's
+      <link linkend="sql-createsubscription-params-with-failover"><literal>failover</literal></link>
+      option is enabled.
+     </para>

It is a bit wordy to keep saying "disabled/enabled"

BEFORE
The slot on the publisher could either be synced to the standbys even
when the subscription's failover option is disabled or could be
disabled for sync even when the subscription's failover option is
enabled.

SUGGESTION
The slot on the publisher could be synced to the standbys even when
the subscription's failover = false or may not be syncing even when
the subscription's failover = true.

======
.../t/040_standby_failover_slots_sync.pl

2.
+# Enable subscription
+$subscriber1->safe_psql('postgres',
+ "ALTER SUBSCRIPTION regress_mysub1 ENABLE");
+
+# Disable failover for enabled subscription
+my ($result, $stdout, $stderr) = $subscriber1->psql('postgres',
+ "ALTER SUBSCRIPTION regress_mysub1 SET (failover = false)");
+ok( $stderr =~ /ERROR:  cannot set failover for enabled subscription/,
+ "altering failover is not allowed for enabled subscription");
+

Currently, those tests are under scope the big comment:

+##################################################
+# Test that changing the failover property of a subscription updates the
+# corresponding failover property of the slot.
+##################################################

But that comment is not quite relevant to these tests. So, add another
one just these:

SUGGESTION:
##################################################
# Test that cannot modify the failover option for enabled subscriptions.
##################################################

======
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).