From: Michael Paquier <michael@paquier.xyz>
To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: Andrew Dunstan <andrew.dunstan@2ndquadrant.com>
Cc: Andres Freund <andres@anarazel.de>
Cc: Peter Eisentraut <peter.eisentraut@2ndquadrant.com>
Cc: Yuli Khodorkovskiy <yuli.khodorkovskiy@crunchydata.com>
Cc: pgsql-bugs@lists.postgresql.org
Subject: Re: BUG #15804: Assertion failure when using logging_collector with EXEC_BACKEND
Date: Tue, 21 May 2019 13:45:12 +0900
Message-ID: <20190521044512.GD1921@paquier.xyz> (raw)
In-Reply-To: <7927.1558364465@sss.pgh.pa.us>
References: <20190518093522.GA19212@paquier.xyz>
<28565.1558196308@sss.pgh.pa.us>
<20190519004344.GA3653@paquier.xyz>
<22995.1558278322@sss.pgh.pa.us>
<27719.1558282181@sss.pgh.pa.us>
<16df9d01-8b03-2664-a18c-16c40186f5ab@2ndQuadrant.com>
<2702.1558289980@sss.pgh.pa.us>
<20190520012728.GC1923@paquier.xyz>
<1664.1558325417@sss.pgh.pa.us>
<7927.1558364465@sss.pgh.pa.us>
On Mon, May 20, 2019 at 11:01:05AM -0400, Tom Lane wrote:
> In other words, the right way to think about this is less "move
> syslogger launch to earlier" and more "move port opening to later".
> I did some cursory testing of that idea with the attached patch,
> which simply relocates the port opening logic to below where
> syslogger start is (though "git diff" insists on presenting it
> differently :-(). I also moved and recommented the emission
> of the "starting ..." log entry. It works under EXEC_BACKEND,
> but I'm not fool enough to believe that that proves it works
> under Windows :-(.
I can see what you have done, no worries.
> One issue with this is that we can't be sure we have sole control
> of the postmaster port number at the time we create shmem.
Couldn't that also be a problem for some users? This means that
there is a window where the port won't be opened but the external PID
file can be found. Some tools could be broken as an effect of that.
> Hence, to avoid undesirable conflicts of shmem, we should change
> things to base the shmem key on the datadir's ID not the port
> number, as was already speculated about in
> https://postgr.es/m/16908.1557521200@sss.pgh.pa.us
This would be actually nice to change as you suggest.
> Another point is that we want to be sure this doesn't change
> the order in which lockfiles are released at shutdown. That
> seems OK (I confirmed by strace'ing that the postmaster's
> final syscalls are still done in the same order) but it could
> use some additional eyeballs on it.
>
> There may be some other reorderings that would be a good idea.
> In particular I'm thinking that the CreateOptsFile call should
> be pushed down, so that it doesn't get written until we know
> that the port number is OK.
Is this thread a good place to discuss all those changes by the way?
After all the recent activity in this area, a new thread and a
discussion for v13 would be I think appropriate. I would rather not
play with the devil for v12.
--
Michael
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To: pgsql-bugs@postgresql.org
Cc: michael@paquier.xyz, tgl@sss.pgh.pa.us, andrew.dunstan@2ndquadrant.com, andres@anarazel.de, peter.eisentraut@2ndquadrant.com, yuli.khodorkovskiy@crunchydata.com, pgsql-bugs@lists.postgresql.org
Subject: Re: BUG #15804: Assertion failure when using logging_collector with EXEC_BACKEND
In-Reply-To: <20190521044512.GD1921@paquier.xyz>
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