Horton

Re: [PoC] pg_upgrade: allow to upgrade publisher node

Amit Kapila <amit.kapila16@gmail.com>

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From: Amit Kapila <amit.kapila16@gmail.com>
To: "Hayato Kuroda (Fujitsu)" <kuroda.hayato@fujitsu.com>
Cc: Andres Freund <andres@anarazel.de>, "Zhijie Hou (Fujitsu)" <houzj.fnst@fujitsu.com>, Dilip Kumar <dilipbalaut@gmail.com>, Peter Smith <smithpb2250@gmail.com>, PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>, Bruce Momjian <bruce@momjian.us>, Julien Rouhaud <rjuju123@gmail.com>, vignesh C <vignesh21@gmail.com>, Masahiko Sawada <sawada.mshk@gmail.com>, Bharath Rupireddy <bharath.rupireddyforpostgres@gmail.com>
Date: 2023-10-10T07:40:38Z
Lists: pgsql-hackers 
On Sat, Oct 7, 2023 at 3:46 AM Amit Kapila <amit.kapila16@gmail.com> wrote:
>
> On Fri, Oct 6, 2023 at 6:30 PM Hayato Kuroda (Fujitsu)
> >
> > Based on that, I added another binary function binary_upgrade_create_logical_replication_slot().
> > This function is similar to pg_create_logical_replication_slot(), but the
> > restart_lsn and confirmed_flush are set to *next* WAL segment. The pointed
> > filename is returned and it is passed to pg_resetwal command.
> >
>
> I am not sure if it is a good idea that a
> binary_upgrade_create_logical_replication_slot() API does the logfile
> name calculation.
>

The other problem is that pg_resetwal removes all pre-existing WAL
files which in this case could lead to the removal of the WAL file
corresponding to restart_lsn. This is because at least the shutdown
checkpoint record will be written after the creation of slots which
could be in the new file used for restart_lsn. Then when we invoke
pg_resetwal, it can remove that file.

One idea to deal with this could be to do the reset WAL stuff
(FindEndOfXLOG(), KillExistingXLOG(), KillExistingArchiveStatus(),
WriteEmptyXLOG()) in a separate function (say in pg_upgrade) and then
create slots. If we do this, then we additionally need an option in
pg_resetwal which skips resetting the WAL as that would have been done
before creating the slots.

-- 
With Regards,
Amit Kapila.

Commits

  1. Fix issues in binary_upgrade_logical_slot_has_caught_up().

  2. Fix a random failure in 003_logical_slots.pl.

  3. Fix a test in 003_logical_slots.

  4. Fix uninitialized slot array access during the upgrade.

  5. Fix the test 003_logical_slots.

  6. Commit b195e6d482 forgot to update meson.build.

  7. Use shorter file names in the upgrade logical slots test.

  8. Migrate logical slots to the new node during an upgrade.

  9. Flush logical slots to disk during a shutdown checkpoint if required.

  10. Prevent possibility of panics during shutdown checkpoint.