Horton

Re: Synchronizing slots from primary to standby

Peter Smith <smithpb2250@gmail.com>

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From: Peter Smith <smithpb2250@gmail.com>
To: Ajin Cherian <itsajin@gmail.com>
Cc: shveta malik <shveta.malik@gmail.com>, Amit Kapila <amit.kapila16@gmail.com>, "Hayato Kuroda (Fujitsu)" <kuroda.hayato@fujitsu.com>, "Drouvot, Bertrand" <bertranddrouvot.pg@gmail.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: 2023-10-06T05:24:04Z
Lists: pgsql-hackers 
Hi Ajin. Thanks for addressing my previous review comments from v19.

I checked all the changes. Below are a few follow-up remarks.

On Thu, Oct 5, 2023 at 7:54 PM Ajin Cherian <itsajin@gmail.com> wrote:
>
> On Wed, Sep 27, 2023 at 2:37 PM Peter Smith <smithpb2250@gmail.com> wrote:
> >
> > Here are some more review comments for the patch v19-0002.

> > 3. get_local_synced_slot_names
> >
> > + for (int i = 0; i < max_replication_slots; i++)
> > + {
> > + ReplicationSlot *s = &ReplicationSlotCtl->replication_slots[i];
> > +
> > + /* Check if it is logical synchronized slot */
> > + if (s->in_use && SlotIsLogical(s) && s->data.synced)
> > + {
> > + for (int j = 0; j < MySlotSyncWorker->dbcount; j++)
> > + {
> >
> > Loop variables are not declared in the common PG code way.
> >
>
> fixed.

Yes, new declarations were added, but some of them (e.g. 'j') could
have been declared at a lower scope closer to where they are being
used.

> > 5. use_slot_in_query
> >
> > +static bool
> > +use_slot_in_query(char *slot_name, Oid *dbids)
> >
> > There are multiple non-standard for-loop variable declarations in this function.
> >
>
> fixed.

Yes, new declarations were added, but some of them (e.g. 'j') could
have been declared at a lower scope closer to where they are being
used.

> > 11. get_remote_invalidation_cause
> >
> > +/*
> > + * Get Remote Slot's invalidation cause.
> > + *
> > + * This gets invalidation cause of remote slot.
> > + */
> > +static ReplicationSlotInvalidationCause
> > +get_remote_invalidation_cause(WalReceiverConn *wrconn, char *slot_name)
> > +{
> >
> > Isn't that function comment just repeating itself?
> >
>
> Fixed.

/remote slot./the remote slot./

> > 27.
> > + /* We are done, free remot_slot_list elements */
> > + foreach(cell, remote_slot_list)
> > + {
> > + RemoteSlot *remote_slot = (RemoteSlot *) lfirst(cell);
> > +
> > + pfree(remote_slot);
> > + }
> >
> > 27a.
> > /remot_slot_list/remote_slot_list/
> >
>
> Fixed.
>
> > ~
> >
> > 27b.
> > Isn't this just the same as the one-liner:
> >
> > list_free_deep(remote_slot_list);

It looks like the #27b comment was accidentally missed (??)

> > 29. remote_connect
> >
> > +/*
> > + * Connect to remote (primary) server.
> > + *
> > + * This uses primary_conninfo in order to connect to primary. For slot-sync
> > + * to work, primary_conninfo is expected to have dbname as well.
> > + */
> > +static WalReceiverConn *
> > +remote_connect()
> >
> > 29a.
> > I felt it might be more helpful to say "GUC primary_conninfo" instead
> > of just 'primary_conninfo' the first time this is mentioned.
> >
>
> fixed.

The changed v21 comment now refers to "GUC PrimaryConnInfo" but I
think that is wrong. The GUC really is called "pnmary_conninfo" ---
PrimaryConnInfo is just the code static variable name.

======
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).