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: Masahiko Sawada <sawada.mshk@gmail.com>, shveta malik <shveta.malik@gmail.com>, Peter Smith <smithpb2250@gmail.com>, Ajin Cherian <itsajin@gmail.com>, Bertrand Drouvot <bertranddrouvot.pg@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: 2024-02-13T12:35:27Z
Lists: pgsql-hackers

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On Tuesday, February 13, 2024 2:51 PM Amit Kapila <amit.kapila16@gmail.com> wrote:
> 
> On Tue, Feb 13, 2024 at 9:38 AM Zhijie Hou (Fujitsu) <houzj.fnst@fujitsu.com>
> wrote:
> >
> > Here is the V85_2 patch set that added the test and fixed one typo,
> > there are no other code changes.
> >
> 
> Few comments on the latest changes:

Thanks for the comments.

> ==============================
> 1.
> +# Confirm that the invalidated slot has been dropped.
> +$standby1->wait_for_log(qr/dropped replication slot "lsub1_slot" of
> +dbid 5/,  $log_offset);
> 
> Is it okay to hardcode dbid 5? I am a bit worried that it can lead to instability in
> the test.
> 
> 2.
> +check_primary_info(WalReceiverConn *wrconn, int elevel) {
> ..
> + bool primary_info_valid;
> 
> I don't think for 0001, we need an elevel as an argument, so let's remove it.
> Additionally, can we change the variable name primary_info_valid to
> primary_slot_valid? Also, can we change the function name to
> validate_remote_info() as the remote can be both primary or standby?
> 
> 3.
> +SyncReplicationSlots(WalReceiverConn *wrconn) {
> +PG_ENSURE_ERROR_CLEANUP(slotsync_failure_callback,
> +PointerGetDatum(wrconn));  {  check_primary_info(wrconn, ERROR);
> +
> + synchronize_slots(wrconn);
> + }
> + PG_END_ENSURE_ERROR_CLEANUP(slotsync_failure_callback,
> PointerGetDatum(wrconn));
> +
> + walrcv_disconnect(wrconn);
> 
> It is better to disconnect in the caller where we have made the connection.

All above comments look good to me.
Here is the V86 patch that addressed above. This version also includes some
other minor changes:

1. Added few comments for the temporary slot creation and XLogGetOldestSegno.
2. Adjusted the doc for the SQL function.
3. Reordered two error messages in slot create function.
4. Fixed few typos.

Thanks Shveta for off-list discussions.

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).