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>, Peter Smith <smithpb2250@gmail.com>
Cc: Masahiko Sawada <sawada.mshk@gmail.com>, shveta malik <shveta.malik@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>, Bertrand Drouvot <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: 2024-03-07T06:30:09Z
Lists: pgsql-hackers

Attachments

On Thursday, March 7, 2024 12:46 PM Amit Kapila <amit.kapila16@gmail.com> wrote:
> 
> On Thu, Mar 7, 2024 at 7:35 AM Peter Smith <smithpb2250@gmail.com>
> wrote:
> >
> > Here are some review comments for v107-0001
> >
> > ======
> > src/backend/replication/slot.c
> >
> > 1.
> > +/*
> > + * Struct for the configuration of standby_slot_names.
> > + *
> > + * Note: this must be a flat representation that can be held in a single chunk
> > + * of guc_malloc'd memory, so that it can be stored as the "extra" data for
> the
> > + * standby_slot_names GUC.
> > + */
> > +typedef struct
> > +{
> > + int slot_num;
> > +
> > + /* slot_names contains nmembers consecutive nul-terminated C strings */
> > + char slot_names[FLEXIBLE_ARRAY_MEMBER];
> > +} StandbySlotConfigData;
> > +
> >
> > 1a.
> > To avoid any ambiguity this 1st field is somehow a slot ID number, I
> > felt a better name would be 'nslotnames' or even just 'n' or 'count',
> >
> 
> We can probably just add a comment above slot_num and that should be
> sufficient but I am fine with 'nslotnames' as well, in anycase let's
> add a comment for the same.

Added.

> 
> >
> > 6b.
> > IMO this function would be tidier written such that the
> > MyReplicationSlot->data.name is passed as a parameter. Then you can
> > name the function more naturally like:
> >
> > IsSlotInStandbySlotNames(const char *slot_name)
> >
> 
> +1. How about naming it as SlotExistsinStandbySlotNames(char
> *slot_name) and pass the slot_name from MyReplicationSlot? Otherwise,
> we need an Assert for MyReplicationSlot in this function.

Changed as suggested.

> 
> Also, can we add a comment like below before the loop:
> + /*
> + * XXX: We are not expecting this list to be long so a linear search
> + * shouldn't hurt but if that turns out not to be true then we can cache
> + * this information for each WalSender as well.
> + */

Added.

Attach the V108 patch set which addressed above and Peter's comments.
I also removed the check for "*" in guc check hook.

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).