Horton

Re: suppressing useless wakeups in logical/worker.c

Nathan Bossart <nathandbossart@gmail.com>

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From: Nathan Bossart <nathandbossart@gmail.com>
To: "Hayato Kuroda (Fujitsu)" <kuroda.hayato@fujitsu.com>
Cc: "pgsql-hackers@postgresql.org" <pgsql-hackers@postgresql.org>
Date: 2022-12-05T17:35:23Z
Lists: pgsql-hackers 
On Mon, Dec 05, 2022 at 01:00:19PM +0000, Hayato Kuroda (Fujitsu) wrote:
> But in your patch, the apply worker calcurates wakeup[LRW_WAKEUP_PING] and
> wakeup[LRW_WAKEUP_TERMINATE] again when it gets SIGHUP, so the worker never sends
> ping with requestReply = true, and never exits due to the timeout.

This is the case for the walreceiver patch, too.  If a SIGHUP arrives just
before we are due to ping the server, the ping wakeup time will be pushed
back.  To me, this seems unlikely to cause any issues in practice unless
the server is being constantly SIGHUP'd.  If we wanted to fix this, we'd
probably need to recompute the wakeup times using the values currently set.
I haven't looked into this too closely, but it doesn't sound tremendously
difficult.  Thoughts?

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

Commits

  1. Improve TimestampDifferenceMilliseconds to cope with overflow sanely.

  2. Code review for commit 05a7be935.