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: Bertrand Drouvot <bertranddrouvot.pg@gmail.com>, shveta malik <shveta.malik@gmail.com>
Cc: Amit Kapila <amit.kapila16@gmail.com>, Masahiko Sawada <sawada.mshk@gmail.com>, Peter Smith <smithpb2250@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: 2024-02-23T09:30:58Z
Lists: pgsql-hackers 
On Friday, February 23, 2024 5:07 PM Bertrand Drouvot <bertranddrouvot.pg@gmail.com> wrote:
> 
> On Fri, Feb 23, 2024 at 02:15:11PM +0530, shveta malik wrote:
> > On Fri, Feb 23, 2024 at 1:28 PM Bertrand Drouvot
> > <bertranddrouvot.pg@gmail.com> wrote:
> > >
> > > Hi,
> > >
> > > Because one could create say the "=" OPERATOR in their own schema,
> > > attach a function to it doing undesired stuff and change the
> > > search_path for the database the sync slot worker connects to.
> > >
> > > Then this new "=" operator would be used (instead of the
> > > pg_catalog.= one), triggering the "undesired" function as superuser.
> >
> > Thanks for the details. I understand it now.  We do not use '=' in our
> > main slots-fetch query but we do use '=' in remote-validation query.
> > See validate_remote_info().
> 
> Oh, right, I missed it during the review.
> 
> > Do you think instead of doing the above, we can override search-path
> > with empty string in the slot-sync case.
> > SImilar to logical apply worker and autovacuum worker case (see
> > InitializeLogRepWorker(), AutoVacWorkerMain()).
> 
> Yeah, we should definitively ensure that any operators being used in the query
> is coming from the pg_catalog schema (could be by setting the search path or
> using the up-thread proposal).
> 
> Setting the search path would prevent any risks in case the query is changed
> later on, so I'd vote for changing the search path in validate_remote_info() and
> in synchronize_slots() to be on the safe side.

I think to set secure search path for remote connection, the standard approach
could be to extend the code in libpqrcv_connect[1], so that we don't need to schema
qualify all the operators in the queries.

And for local connection, I agree it's also needed to add a
SetConfigOption("search_path", "" call in the slotsync worker.

[1]
libpqrcv_connect
...
	if (logical)
...
		res = libpqrcv_PQexec(conn->streamConn,
							  ALWAYS_SECURE_SEARCH_PATH_SQL);

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).