Horton

Re: wake up logical workers after ALTER SUBSCRIPTION

Nathan Bossart <nathandbossart@gmail.com>

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From: Nathan Bossart <nathandbossart@gmail.com>
To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: Melih Mutlu <m.melihmutlu@gmail.com>, Thomas Munro <thomas.munro@gmail.com>, "Hayato Kuroda (Fujitsu)" <kuroda.hayato@fujitsu.com>, "pgsql-hackers@postgresql.org" <pgsql-hackers@postgresql.org>
Date: 2022-12-14T23:17:27Z
Lists: pgsql-hackers 
On Wed, Dec 14, 2022 at 02:02:58PM -0500, Tom Lane wrote:
> Maybe we could have workers that are exiting for that reason set a
> flag saying "please restart me without delay"?

That helps a bit, but there are still delays when starting workers for new
subscriptions.  I think we'd need to create a new array in shared memory
for subscription OIDs that need their workers started immediately.

I'm not totally sure this is worth the effort.  These delays surface in the
tests because the workers are started so frequently.  In normal operation,
this is probably unusual, so the launcher would typically start new workers
immediately.  But if you and/or others feel this is worthwhile, I don't
mind working on the patch.

-- 
Nathan Bossart
Amazon Web Services: https://aws.amazon.com

Commits

  1. Avoid type cheats for invalid dsa_handles and dshash_table_handles.

  2. Track logrep apply workers' last start times to avoid useless waits.

  3. Check for two_phase change at end of process_syncing_tables_for_apply.

  4. Wake up a subscription's replication worker processes after DDL.