From: "Petteri Räty" <betelgeuse@gentoo.org>
To: mongrel-unicorn@rubyforge.org
Subject: Re: pid file deleted briefly when doing hot restart
Date: Mon, 26 Nov 2012 12:39:56 +0200 [thread overview]
Message-ID: <50B346FC.1040502@gentoo.org> (raw)
In-Reply-To: <20121126004301.GA3876@dcvr.yhbt.net>
On 26.11.2012 2.43, Eric Wong wrote:
> Petteri Räty <betelgeuse@gentoo.org> wrote:
>> What follows are all the write actions related to unicorn pid file when
>> doing a hot restart. Seems like a bug to me that unicorn is deleting the
>> pid file before writing the new file. Is there a reason for it? It seems
>> to go against that rename that aims for an atomic replace that would
>> always ensure the pid file is there.
>
> Unfortunately, pid files are inherently racy. However, I
> seem to recall a pid file not existing for a brief moment was needed
> to allow some nginx-based scripts to work.
>
Would you be open for a config switch to avoid this behavior?
Can you say if lib/unicorn/http_server.rb:196 is the correct spot?
The use case here is that with health monitors wouldn't have a window
where a pid file does not exist. With a hot restart it should always be
possible to have a pid file that points to either the old or the new master.
> I think unicorn differs a bit from nginx here:
>
> nginx uses rename() to clear the way for a new pid file. Like unicorn,
> this still leaves a window where no pid file exists.
>
Looking at the inotify log it seems the reason pid file does not exist
is an explicit delete and not due to rename. It happens a couple seconds
earlier also so the window is possible to hit even with a periodic poller.
Regards,
Petteri
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next prev parent reply other threads:[~2012-11-26 10:40 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-11-25 23:27 pid file deleted briefly when doing hot restart Petteri Räty
2012-11-26 0:43 ` Eric Wong
2012-11-26 10:39 ` Petteri Räty [this message]
2012-11-26 18:24 ` Eric Wong
2012-11-26 23:56 ` Petteri Räty
2012-11-27 0:35 ` Eric Wong
2012-11-27 1:49 ` Petteri Räty
2012-11-27 2:02 ` Eric Wong
2012-11-27 16:11 ` Petteri Räty
2012-11-27 21:51 ` Eric Wong
2012-11-27 1:50 ` Petteri Räty
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