From: | Antonin Houska <ah(at)cybertec(dot)at> |
---|---|
To: | Andres Freund <andres(at)anarazel(dot)de>, Michael Paquier <michael(at)paquier(dot)xyz>, pgsql-hackers(at)postgresql(dot)org, Alvaro Herrera <alvherre(at)2ndquadrant(dot)com> |
Subject: | Re: 2pc leaks fds |
Date: | 2020-04-08 07:26:37 |
Message-ID: | 70058.1586330797@antos |
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Lists: | pgsql-hackers |
Antonin Houska <ah(at)cybertec(dot)at> wrote:
> Andres Freund <andres(at)anarazel(dot)de> wrote:
> > But I'm not sure it's quite the right idea. I'm not sure I fully
> > understand the design of 0dc8ead46, but it looks to me like it's
> > intended to allow users of the interface to have different ways of
> > opening files. If we just close() the fd that'd be a bit more limited.
>
> It should have allowed users to have different ways to *locate the segment*
> file. The WALSegmentOpen callback could actually return file path instead of
> the file descriptor and let WALRead() perform the opening/closing, but then
> the WALRead function would need to be aware whether it is executing in backend
> or in frontend (so it can use the correct function to open/close the file).
Well, #ifdef FRONTEND can be used to distinguish the caller of
WALRead(). However now that I tried to adjust the API, I see that
pg_waldump.c:WALDumpOpenSegment uses specific logic to open the file. So if
the callback only returned the file name, there would be no suitable place for
the things that WALDumpOpenSegment does.
--
Antonin Houska
Web: https://www.cybertec-postgresql.com
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