Horton

RE: Synchronizing slots from primary to standby

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

View thread View on postgr.es
From: "Zhijie Hou (Fujitsu)" <houzj.fnst@fujitsu.com>
To: Bertrand Drouvot <bertranddrouvot.pg@gmail.com>
Cc: Amit Kapila <amit.kapila16@gmail.com>, Peter Smith <smithpb2250@gmail.com>, shveta malik <shveta.malik@gmail.com>, Masahiko Sawada <sawada.mshk@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: 2024-03-04T13:26:13Z
Lists: pgsql-hackers 
On Monday, March 4, 2024 7:22 PM Bertrand Drouvot <bertranddrouvot.pg@gmail.com> wrote:
> 
> Hi,
> 
> On Sun, Mar 03, 2024 at 07:56:32AM +0000, Zhijie Hou (Fujitsu) wrote:
> > Here is the V104 patch which addressed above and Peter's comments.
> 
> Thanks!
> 
> A few more random comments:

Thanks for the comments!

> 
> 1 ===
> 
> +        The function may be blocked if the specified slot is a failover
> + enabled
> 
> s/blocked/waiting/ ?

Changed.

> 
> 2 ===
> 
> +                * specified slot when waiting for them to catch up. See
> +                * StandbySlotsHaveCaughtup for details.
> 
> s/StandbySlotsHaveCaughtup/StandbySlotsHaveCaughtup()/ ?

Changed.

> 
> 3 ===
> 
> +       /* Now verify if the specified slots really exist and have
> + correct type */
> 
> remove "really"?

Changed.

> 
> 4 ===
> 
> +       /*
> +        * Don't need to wait for the standbys to catch up if there is no value in
> +        * standby_slot_names.
> +        */
> +       if (standby_slot_names_list == NIL)
> +               return true;
> +
> +       /*
> +        * Don't need to wait for the standbys to catch up if we are on a
> standby
> +        * server, since we do not support syncing slots to cascading standbys.
> +        */
> +       if (RecoveryInProgress())
> +               return true;
> +
> +       /*
> +        * Don't need to wait for the standbys to catch up if they are already
> +        * beyond the specified WAL location.
> +        */
> +       if (!XLogRecPtrIsInvalid(standby_slot_oldest_flush_lsn) &&
> +               standby_slot_oldest_flush_lsn >= wait_for_lsn)
> +               return true;
> 
> What about using OR conditions instead?
> 
> 5 ===
> 
> +static bool
> +NeedToWaitForStandby(XLogRecPtr target_lsn, XLogRecPtr flushed_lsn,
> +                                        uint32 *wait_event)
> 
> Not a big deal but does it need to return a bool? (I mean it all depends of the
> *wait_event value). Is it for better code readability in the caller?
> 
> 6 ===
> 
> +static bool
> +NeedToWaitForWal(XLogRecPtr target_lsn, XLogRecPtr flushed_lsn,
> +                                uint32 *wait_event)
> 
> Same questions as for NeedToWaitForStandby().

I also feel the current style looks a bit cleaner, so didn’t change these.

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).