From: "Petteri Räty" <betelgeuse@gentoo.org>
To: mongrel-unicorn@rubyforge.org
Subject: Re: Issues with PID file renaming
Date: Wed, 11 Dec 2013 00:44:43 +0200 [thread overview]
Message-ID: <52A7995B.7010905@gentoo.org> (raw)
In-Reply-To: <20131210195255.GA26226@dcvr.yhbt.net>
On 10.12.2013 21.52, Eric Wong wrote:
> Petteri Räty <betelgeuse@gentoo.org> wrote:
>> On 26.11.2013 3.20, Eric Wong wrote:
>>> How about having the old process create a hard link to .oldbin,
>>> and having the new one override the pid if Process.ppid == pid file?
>>> The check is still racy, but that's what pid files are :<
>>
>> Isn't it possible to always keep a valid pid file by using the fact that
>> mv is atomic? Basically the new process writes the pid first to a temp
>> file and then moves it over the old pid file after having hard linked
>> the file to .oldbin?
>>
>> $ echo "1" > foo.pid
>> $ ln foo.pid foo.oldpid
>> $ echo "2" > tmp
>> $ mv tmp foo.pid
>> $ cat *pid
>> 1
>> 2
>
> It's possible, but is it worth it? Having both pid files point to the
> same pid is still wrong.
>
At least for pid based monitoring tools it is (I do agree with others
that you should also be monitoring http though). For example monit
requires that you give it a pid file. Why is it wrong for them to point
to the same pid? Seems ok to me especially since they share the inode.
Any way I think this is better than there being no pid file. After all
we are doing a zero downtime deploy which means there's always a valid
process.
Regards,
Petteri
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next prev parent reply other threads:[~2013-12-10 22:44 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-11-26 1:00 Issues with PID file renaming Jimmy Soho
2013-11-26 1:20 ` Eric Wong
2013-11-26 1:40 ` Michael Fischer
2013-11-26 2:07 ` Eric Wong
2013-12-10 12:46 ` Petteri Räty
2013-12-10 19:52 ` Eric Wong
2013-12-10 22:44 ` Petteri Räty [this message]
2013-12-11 13:54 ` Michael Fischer
2013-12-12 19:15 ` Petteri Räty
2013-12-12 20:51 ` Eric Wong
2013-11-26 1:42 ` Michael Fischer
2013-11-26 4:55 ` Jimmy Soho
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