Horton

Re: Synchronizing slots from primary to standby

Amit Kapila <amit.kapila16@gmail.com>

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From: Amit Kapila <amit.kapila16@gmail.com>
To: Masahiko Sawada <sawada.mshk@gmail.com>
Cc: shveta malik <shveta.malik@gmail.com>, "Zhijie Hou (Fujitsu)" <houzj.fnst@fujitsu.com>, Peter Smith <smithpb2250@gmail.com>, Bertrand Drouvot <bertranddrouvot.pg@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: 2024-02-01T09:05:15Z
Lists: pgsql-hackers 
On Wed, Jan 31, 2024 at 9:20 PM Masahiko Sawada <sawada.mshk@gmail.com> wrote:
>
> On Wed, Jan 31, 2024 at 7:42 PM Amit Kapila <amit.kapila16@gmail.com> wrote:
> >
> > On Wed, Jan 31, 2024 at 2:02 PM Masahiko Sawada <sawada.mshk@gmail.com> wrote:
> > >
> > > Thank you for updating the patches. As for the slotsync worker patch,
> > > is there any reason why 0001, 0002, and 0004 patches are still
> > > separated?
> > >
> >
> > No specific reason, it could be easier to review those parts.
>
> Okay, I think we can merge 0001 and 0002 at least as we don't need
> bgworker codes.
>

Agreed, and I am fine with merging 0001, 0002, and 0004 as suggested
by you though I have a few minor comments on 0002 and 0004. I was
thinking about what will be a logical way to split the slot sync
worker patch (combined result of 0001, 0002, and 0004), and one idea
occurred to me is that we can have the first patch as
synchronize_solts() API and the functionality required to implement
that API then the second patch would be a slot sync worker which uses
that API to synchronize slots and does all the required validations.
Any thoughts?

Few minor comments on 0002 and 0004
================================
1. The comments above HandleChildCrash() should mention about slot sync worker

2.
--- a/src/backend/storage/lmgr/proc.c
+++ b/src/backend/storage/lmgr/proc.c
@@ -42,6 +42,7 @@
 #include "replication/slot.h"
 #include "replication/syncrep.h"
 #include "replication/walsender.h"
+#include "replication/logicalworker.h"

...
--- a/src/backend/utils/init/postinit.c
+++ b/src/backend/utils/init/postinit.c
@@ -43,6 +43,7 @@
 #include "postmaster/autovacuum.h"
 #include "postmaster/postmaster.h"
 #include "replication/slot.h"
+#include "replication/logicalworker.h"

These new includes don't appear to be in alphabetical order.

3.
+ /* We can not have logical without replication */
+ if (!replication)
+ Assert(!logical);

I think we can cover both these conditions via Assert

-- 
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).