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: 2022-12-18T23:36:07Z
Lists: pgsql-hackers 
On Thu, Dec 15, 2022 at 02:47:21PM -0800, Nathan Bossart wrote:
> I tried setting wal_retrieve_retry_interval to 1ms for all TAP tests
> (similar to what was done in 2710ccd), and I noticed that the recovery
> tests consistently took much longer.  Upon further inspection, it looks
> like the same (or a very similar) race condition described in e5d494d's
> commit message [0].  With some added debug logs, I see that all of the
> callers of MaybeStartWalReceiver() complete before SIGCHLD is processed, so
> ServerLoop() waits for a minute before starting the WAL receiver.
> 
> A simple fix is to have DetermineSleepTime() take the WalReceiverRequested
> flag into consideration.  The attached 0002 patch shortens the sleep time
> to 100ms if it looks like we are waiting on a SIGCHLD.  I'm not certain
> this is the best approach, but it seems to fix the tests.

This seems to have somehow broken the archiving tests on Windows, so
obviously I owe some better analysis here.  I didn't see anything obvious
in the logs, but I will continue to dig.

-- 
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.