Horton

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

Julien Rouhaud <rjuju123@gmail.com>

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From: Julien Rouhaud <rjuju123@gmail.com>
To: Amit Kapila <amit.kapila16@gmail.com>
Cc: Masahiko Sawada <sawada.mshk@gmail.com>, "Hayato Kuroda (Fujitsu)" <kuroda.hayato@fujitsu.com>, PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>, vignesh C <vignesh21@gmail.com>
Date: 2023-08-07T05:59:31Z
Lists: pgsql-hackers 
On Mon, Aug 07, 2023 at 09:24:02AM +0530, Amit Kapila wrote:
>
> I think autovacuum is not enabled during the upgrade. See comment "Use
> -b to disable autovacuum." in start_postmaster(). However, I am not
> sure if there can't be any additional WAL from checkpointer or
> bgwriter. Checkpointer has a code that ensures that if there is no
> important WAL activity then it would be skipped. Similarly, bgwriter
> also doesn't LOG xl_running_xacts unless there is an important
> activity. I feel if there is a chance of any WAL activity during the
> upgrade, we need to either change the check to ensure such WAL records
> are expected or document the same in some way.

Unless I'm missing something I don't see what prevents something to connect
using the replication protocol and issue any query or even create new
replication slots?

Note also that as complained a few years ago nothing prevents a bgworker from
spawning up during pg_upgrade and possibly corrupt the upgraded cluster if
multixid are assigned.  If publications are preserved wouldn't it mean that
such bgworkers could also lead to data loss?

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.