Unicorn in the jail

Unicorn in the jail

[Tatsuya Ono]

I ran into a problem when sending USR2 signal to master process which
is listening a TCP port. It shows the following error in log.

err: adding listener failed addr=0.0.0.0:3010 (in use)

I found similar error reported on this mailing list and yes, the host
I got the error was in the FreeBSD jail.
http://rubyforge.org/pipermail/mongrel-unicorn/2009-December/000205.html
http://rubyforge.org/pipermail/mongrel-unicorn/2009-December/000212.html

I dug into the problem and found some interesting thing. I want to
share it and the solution here.

* Why does it happen in the Jail?
When you bind 0.0.0.0 address to the socket on a Jail host, Jail
doesn't bind 0.0.0.0. Instead of it, it binds to the IP address of the
host such as 10.100.1.50, 192.168.1.50, etc.
Then the problem happens in Unicorn::HttpServer#inherit_listeners!
when it gets signal like USR2.
https://github.com/defunkt/unicorn/blob/406b8b0e2ed6e5be34d8ec3cd4b16048233c2856/lib/unicorn/http_server.rb#L703-731

Here you get 10.100.1.50 (for example) as inherited address from
ENV['UNICORN_FD'] but 0.0.0.0. So Unicorn tries to bind to 0.0.0.0
(again) at line 728. Then it fails because it is actually in use.

* How to solve the issue?
Thankfully unicorn.conf is ruby script so that I could write a logic
for Jail hosts without specifying IP address of those hosts (which we
want to avoid since we deploy it multiple servers). I share the
configuration file.
https://gist.github.com/1122965

Then Unicorn flies in the jail happily.

Tatsuya Ono
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Re: Unicorn in the jail

[Eric Wong]

Thanks!  I've pushed out the following patch and updated the site:

>From ec8a8f32d257290aac377f1c7b1c496e1df75f73 Mon Sep 17 00:00:00 2001
From: Eric Wong <normalperson@yhbt.net>
Date: Wed, 3 Aug 2011 11:00:28 -0700
Subject: [PATCH] KNOWN_ISSUES: add link to FreeBSD jail workaround notes

Thanks to Tatsuya Ono on the unicorn mailing list.
---
 KNOWN_ISSUES |    3 +++
 1 files changed, 3 insertions(+), 0 deletions(-)

diff --git a/KNOWN_ISSUES b/KNOWN_ISSUES
index 2bd4151..f323c68 100644
--- a/KNOWN_ISSUES
+++ b/KNOWN_ISSUES
@@ -3,6 +3,9 @@
 Occasionally odd {issues}[link:ISSUES.html] arise without a transparent or
 acceptable solution.  Those issues are documented here.
 
+* Issues with FreeBSD jails can be worked around as documented by Tatsuya Ono:
+  http://mid.gmane.org/CAHBuKRj09FdxAgzsefJWotexw-7JYZGJMtgUp_dhjPz9VbKD6Q@mail.gmail.com
+
 * PRNGs (pseudo-random number generators) loaded before forking
   (e.g. "preload_app true") may need to have their internal state
   reset in the after_fork hook.  Starting with \Unicorn 3.6.1, we
-- 
Eric Wong
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Re: Unicorn in the jail

[Tatsuya Ono]

Thank you, Eric!

Tatsuya

On 3 August 2011 19:03, Eric Wong <normalperson@yhbt.net> wrote:
>
> Thanks!  I've pushed out the following patch and updated the site:
>
> >From ec8a8f32d257290aac377f1c7b1c496e1df75f73 Mon Sep 17 00:00:00 2001
> From: Eric Wong <normalperson@yhbt.net>
> Date: Wed, 3 Aug 2011 11:00:28 -0700
> Subject: [PATCH] KNOWN_ISSUES: add link to FreeBSD jail workaround notes
>
> Thanks to Tatsuya Ono on the unicorn mailing list.
> ---
>  KNOWN_ISSUES |    3 +++
>  1 files changed, 3 insertions(+), 0 deletions(-)
>
> diff --git a/KNOWN_ISSUES b/KNOWN_ISSUES
> index 2bd4151..f323c68 100644
> --- a/KNOWN_ISSUES
> +++ b/KNOWN_ISSUES
> @@ -3,6 +3,9 @@
>  Occasionally odd {issues}[link:ISSUES.html] arise without a transparent or
>  acceptable solution.  Those issues are documented here.
>
> +* Issues with FreeBSD jails can be worked around as documented by Tatsuya Ono:
> +  http://mid.gmane.org/CAHBuKRj09FdxAgzsefJWotexw-7JYZGJMtgUp_dhjPz9VbKD6Q@mail.gmail.com
> +
>  * PRNGs (pseudo-random number generators) loaded before forking
>   (e.g. "preload_app true") may need to have their internal state
>   reset in the after_fork hook.  Starting with \Unicorn 3.6.1, we
> --
> Eric Wong
> _______________________________________________
> Unicorn mailing list - mongrel-unicorn@rubyforge.org
> http://rubyforge.org/mailman/listinfo/mongrel-unicorn
> Do not quote signatures (like this one) or top post when replying
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