Horton

Re: Add client connection check during the execution of the query

Thomas Munro <thomas.munro@gmail.com>

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From: Thomas Munro <thomas.munro@gmail.com>
To: Andres Freund <andres@anarazel.de>
Cc: Maksim Milyutin <milyutinma@gmail.com>, "tsunakawa.takay@fujitsu.com" <tsunakawa.takay@fujitsu.com>, pgsql-hackers <pgsql-hackers@postgresql.org>, Tatsuo Ishii <ishii@sraoss.co.jp>, Tom Lane <tgl@sss.pgh.pa.us>, Zhihong Yu <zyu@yugabyte.com>
Date: 2022-01-14T06:30:07Z
Lists: pgsql-hackers

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On Fri, Jan 14, 2022 at 4:35 PM Andres Freund <andres@anarazel.de> wrote:
> The more I think about it, the less I see why we *ever* need to re-arm the
> latch in pq_check_connection() in this approach. pq_check_connection() is only
> used from from ProcessInterrupts(), and there's plenty things inside
> ProcessInterrupts() that can cause latches to be reset (e.g. parallel message
> processing causing log messages to be sent to the client, causing network IO,
> which obviously can do a latch reset).

Thanks for the detailed explanation.  I guess I was being overly
cautious and a little myopic, "leave things exactly the way you found
them", so I didn't have to think about any of that.  I see now that
the scenario I was worrying about would be a bug in whatever
latch-wait loop happens to reach this code.  Alright then, here is
just... one... more... patch, this time consuming any latch that gets
in the way and retrying, with no restore.

Commits

  1. Add WL_SOCKET_CLOSED for socket shutdown events.

  2. Use WL_SOCKET_CLOSED for client_connection_check_interval.

  3. Detect POLLHUP/POLLRDHUP while running queries.

  4. Improve timeout.c's handling of repeated timeout set/cancel.