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: Dilip Kumar <dilipbalaut@gmail.com>, Amit Kapila <amit.kapila16@gmail.com>, Masahiko Sawada <sawada.mshk@gmail.com>, shveta malik <shveta.malik@gmail.com>, Bertrand Drouvot <bertranddrouvot.pg@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>, Ajin Cherian <itsajin@gmail.com>, Alvaro Herrera <alvherre@alvh.no-ip.org>
Date: 2024-01-10T01:29:21Z
Lists: pgsql-hackers 
Here are some review comments for the patch v58-0001

======
doc/src/sgml/catalogs.sgml

1.
+      <para>
+       If true, the associated replication slots (i.e. the main slot and the
+       table sync slots) in the upstream database are enabled to be
+       synchronized to the physical standbys.
+      </para></entry>

It seems the other single-sentence descriptions on this page have no
period (.) so for consistency maybe you should remove it here also.

======
src/backend/commands/subscriptioncmds.c

2. AlterSubscription

+ /*
+ * Do not allow changing the failover state if the
+ * subscription is enabled. This is because the failover
+ * state of the slot on the publisher cannot be modified if
+ * the slot is currently being acquired by the apply
+ * worker.
+ */

/being acquired/acquired/

~~~

3.
values[Anum_pg_subscription_subfailover - 1] =
BoolGetDatum(opts.failover);
replaces[Anum_pg_subscription_subfailover - 1] = true;

/*
* The failover state of the slot should be changed after
* the catalog update is completed.
*/
set_failover = true;
AFAICT you don't need to introduce a new variable 'set_failover'.
Instead, you can test like:

BEFORE
if (set_failover)

AFTER
if (replaces[Anum_pg_subscription_subfailover - 1])

======
src/backend/replication/logical/tablesync.c

4.
  walrcv_create_slot(LogRepWorkerWalRcvConn,
     slotname, false /* permanent */ , false /* two_phase */ ,
+    MySubscription->failover /* failover */ ,
     CRS_USE_SNAPSHOT, origin_startpos);

The "/* failover */ comment is unnecessary now that you pass the
boolean field with the same descriptive name.

======
src/include/catalog/pg_subscription.h

5. CATALOG

+ bool subfailover; /* True if the associated replication slots
+ * (i.e. the main slot and the table sync
+ * slots) in the upstream database are enabled
+ * the upstream database are enabled to be
+ * synchronized to the physical standbys. */
+

The wording of the comment is broken (it says "are enabled" 2x).

SUGGESTION
True if the associated replication slots (i.e. the main slot and the
table sync slots) in the upstream database are enabled to be
synchronized to the physical standbys.

~~~

6. Subscription

+ bool failover; /* Indicates if the associated replication
+ * slots (i.e. the main slot and the table sync
+ * slots) in the upstream database are enabled
+ * to be synchronized to the physical
+ * standbys. */

This comment can say "True if...", so it will be the same as the
earlier CATALOG comment for 'subfailover'.

======
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).