From: | Craig Ringer <craig(at)2ndquadrant(dot)com> |
---|---|
To: | PostgreSQL Hackers <pgsql-hackers(at)postgresql(dot)org> |
Cc: | Andres Freund <andres(at)anarazel(dot)de> |
Subject: | Persistent wait event sets and socket changes |
Date: | 2017-07-31 06:08:58 |
Message-ID: | CAMsr+YG8zjxu6WfAAA-i33PQ17jvgSO7_CfSh9cncg_kRQ2NDw@mail.gmail.com |
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Lists: | pgsql-hackers |
Hi all
I've been looking into the wait event set interface added in 9.6 with an
eye to using it in an extension that maintains a set of non-blocking libpq
connections to other PostgreSQL instances.
In the process I've been surprised to find that there does not appear to be
any interface to remove a socket once added to the wait event set, or
replace it with a new socket.
ModifyWaitEvent(...) doesn't take a pgsocket. There doesn't seem to be a
way to remove an event from the set either.
Discussion in
https://www.postgresql.org/message-id/flat/20160114143931.GG10941%40awork2.anarazel.de
talks about a proposed SetSocketToWaitOn(...)/AddSocketToWaitSet and
RemoveSocketFromWaitSet etc. But it looks like it petered out and went
nowhere, apparently mainly due to not being needed by any current core
users.
See:
I'd like to add such interfaces at some point, but for now can work around
it by destroying and re-creating the wait event set when the fd-set
changes. So I'm posting mostly to confirm that it's not supposed to work,
and ask if anyone thinks I should submit a comment patch to latch.c
documenting it.
--
Craig Ringer http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Training & Services
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