Horton

RE: Synchronizing slots from primary to standby

Zhijie Hou (Fujitsu) <houzj.fnst@fujitsu.com>

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From: "Zhijie Hou (Fujitsu)" <houzj.fnst@fujitsu.com>
To: Amit Kapila <amit.kapila16@gmail.com>
Cc: Bertrand Drouvot <bertranddrouvot.pg@gmail.com>, shveta malik <shveta.malik@gmail.com>, Ajin Cherian <itsajin@gmail.com>, Peter Smith <smithpb2250@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: 2024-04-02T07:20:46Z
Lists: pgsql-hackers

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On Tuesday, April 2, 2024 8:35 AM Zhijie Hou (Fujitsu) <houzj.fnst@fujitsu.com> wrote:
> 
> On Monday, April 1, 2024 7:30 PM Amit Kapila <amit.kapila16@gmail.com>
> wrote:
> >
> > On Mon, Apr 1, 2024 at 6:26 AM Zhijie Hou (Fujitsu)
> > <houzj.fnst@fujitsu.com>
> > wrote:
> > >
> > > On Friday, March 29, 2024 2:50 PM Amit Kapila
> > > <amit.kapila16@gmail.com>
> > wrote:
> > > >
> > >
> > > >
> > > >
> > > > 2.
> > > > +extern XLogRecPtr pg_logical_replication_slot_advance(XLogRecPtr
> > moveto,
> > > > +   bool *found_consistent_point);
> > > > +
> > > >
> > > > This API looks a bit awkward as the functionality doesn't match
> > > > the name. How about having a function with name
> > > > LogicalSlotAdvanceAndCheckReadynessForDecoding(moveto,
> > > > ready_for_decoding) with the same functionality as your patch has
> > > > for
> > > > pg_logical_replication_slot_advance() and then invoke it both from
> > > > pg_logical_replication_slot_advance and slotsync.c. The function
> > > > name is too big, we can think of a shorter name. Any ideas?
> > >
> > > How about LogicalSlotAdvanceAndCheckDecodingState() Or just
> > > LogicalSlotAdvanceAndCheckDecoding()?
> > >
> >
> > It is about snapbuild state, so how about naming the function as
> > LogicalSlotAdvanceAndCheckSnapState()?
> 
> It looks better to me, so changed.
> 
> >
> > I have made quite a few cosmetic changes in comments and code. See
> > attached. This is atop your latest patch. Can you please review and
> > include these changes in the next version?
> 
> Thanks, I have reviewed and merged them.
> Attach the V5 patch set which addressed above comments and ran pgindent.

I added one test in 040_standby_failover_slots_sync.pl in 0002 patch, which can
reproduce the data loss issue consistently on my machine. It may not reproduce
in some rare cases if concurrent xl_running_xacts are written by bgwriter, but
I think it's still valuable if it can verify the fix in most cases. The test
will fail if directly applied on HEAD, and will pass after applying atop of
0001.

Best Regards,
Hou zj

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).