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: Melih Mutlu <m.melihmutlu@gmail.com>
Cc: Thomas Munro <thomas.munro@gmail.com>, "Hayato Kuroda (Fujitsu)" <kuroda.hayato@fujitsu.com>, "pgsql-hackers@postgresql.org" <pgsql-hackers@postgresql.org>
Date: 2022-12-06T19:25:51Z
Lists: pgsql-hackers

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Thanks for reviewing!

On Tue, Dec 06, 2022 at 07:44:46PM +0300, Melih Mutlu wrote:
> Is it really necessary to wake logical workers up when renaming other than
> subscription or publication? address.objectId will be a valid subid only
> when renaming a subscription.

Oops, that is a mistake.  I only meant to wake up the workers for ALTER
SUBSCRIPTION RENAME.  I think I've fixed this in v6.

> - When the state is SYNCDONE and the apply worker has to wake up to change
> the state to READY.
> 
> I think we already call logicalrep_worker_wakeup_ptr wherever it's needed
> for the above cases? What am I missing here?

IIUC we must restart all the apply workers for a subscription to enable
two_phase mode.  It looks like finish_sync_worker() only wakes up its own
apply worker.  I moved this logic to where the sync worker marks the state
as SYNCDONE and added a check that two_phase mode is pending.  Even so,
there can still be unnecessary wakeups, but this adjustment should limit
them.

-- 
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.