From: "Petteri Räty" <betelgeuse@gentoo.org>
To: mongrel-unicorn@rubyforge.org
Subject: Re: pid file deleted briefly when doing hot restart
Date: Tue, 27 Nov 2012 01:56:18 +0200 [thread overview]
Message-ID: <50B401A2.6060504@gentoo.org> (raw)
In-Reply-To: <20121126182438.GA22060@dcvr.yhbt.net>
On 26.11.2012 20.24, Eric Wong wrote:
>
>> 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.
>
> Then, doesn't nginx have the same problem?
>
nginx doens't have the same problem as I show later. Even if it I
restart/reload nginx very infrequently. Unicorn has to be hot restarted
every time we change our application code and happens frequently.
>>> 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.
>
> Is matching nginx rename behavior enough to solve the problem?
>
> Matching nginx behavior can become the default if it solves your problem.
>
nginx does not explicitly unlink the old pid file before it renames it
out of the way so yes matching nginx in that regard changes the behavior
exactly how I originally asked but you were against that. Maybe the
point is moot though.
This is from a combo of USR2, WINCH, QUIT sent from htop to the master
process:
2012-11-27 01:44:25 +0200
[:moved_from, :move]
"nginx.pid"
2012-11-27 01:44:25 +0200
[:moved_to, :move]
"nginx.pid.oldbin"
2012-11-27 01:44:25 +0200
[:create]
"nginx.pid"
2012-11-27 01:44:25 +0200
[:open]
"nginx.pid"
2012-11-27 01:44:25 +0200
[:modify]
"nginx.pid"
2012-11-27 01:44:25 +0200
[:close_write, :close]
"nginx.pid"
2012-11-27 01:45:31 +0200
[:delete]
"nginx.pid.oldbin"
The window here is much smaller than for the current unicorn behavior.
Regards,
Petteri
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next prev parent reply other threads:[~2012-11-26 23:56 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
2012-11-26 18:24 ` Eric Wong
2012-11-26 23:56 ` Petteri Räty [this message]
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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