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From: Eric Wong <normalperson@yhbt.net>
To: mongrel-unicorn@rubyforge.org
Cc: Pierre Baillet <oct@fotonauts.com>
Subject: Re: Fwd: Support for Soft Timeout in Unicorn
Date: Thu, 3 Jun 2010 18:22:46 +0000	[thread overview]
Message-ID: <20100603182246.GB19649@dcvr.yhbt.net> (raw)
In-Reply-To: <20100603173749.GA19649@dcvr.yhbt.net>

Pierre Baillet wrote:
> We use Unicorn at fotopedia since yesterday in production. We switched from
> Passenger due to an issue in the way Passenger was handling some error in
> our main application. Things run very well on Unicorn.
> We have also modified Unicorn to handle a soft timeout for its workers. The
> Unicorn timeout was killing the workers without any chance for us to catch
> the Rails stack trace and identify the issue. I've forked and branched
> Unicorn from github and added a soft_timeout configuration value that is
> used for long running workers.
> The workers now handle SIGABRT and will raise an exception. This will crash
> the Rails application if it can be crashed and force the framework to dump
> the stack trace in the logs. Let me know if this might be useful for other
> people and, why not, integrate that in the main Unicorn code !

Hi Pierre,

I'm thinking there's a better way to do this without involving the
master process.

The current timeout implementation[1] is really the last resort,
point-of-no-return situations when the workers are completely
stuck/blocked and cannot respond to other signals[2].  If the worker can
respond to SIGABRT (especially going through the interpreter and raising
an exception), then that means it could technically respond to
Thread#raise, too...

Unfortunately, the current core Ruby timeout implementation is extremely
naive and inefficient.  It shouldn't be hard to write a better timeout
implementation that reuses a single timer Thread which can be rearmed
with every request.

This would be doable as middleware, too, and if done carefully, even
safely reusable in multi-threaded web servers.  This would be a good
addition to rack-contrib, even.  I might consider doing it myself if I
had time.

[1] - I'm not completely happy with "needing" the current timeout
      implementation in the first place.  I will at least redo it
      at some point (after Unicorn 1.x) to gain some
      scalability/performance (and perhaps lose some portability).

[2] - SIGKILL and SIGSTOP are special, userspace has no mechanism
      to block/catch/ignore those signals, so we rely on the master
      process to deliver them.

Eric Wong
Unicorn mailing list - mongrel-unicorn@rubyforge.org
Do not quote signatures (like this one) or top post when replying

  parent reply	other threads:[~2010-06-03 18:25 UTC|newest]

Thread overview: 13+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2010-06-03 17:37 Fwd: Support for Soft Timeout in Unicorn Eric Wong
2010-06-03 18:06 ` Pierre Baillet
2010-06-03 18:22 ` Eric Wong [this message]
2010-06-03 18:32   ` Fwd: " Pierre Baillet
2010-06-03 18:47     ` Eric Wong
2010-06-03 19:38       ` Chris Wanstrath
2010-06-03 19:40         ` Pierre Baillet
2010-06-09 13:17           ` Pierre Baillet
2010-06-11  1:56             ` Eric Wong
2010-06-04 20:59         ` Eric Wong
2010-06-18 20:13           ` Ryan Tomayko
2010-06-18 21:48             ` Eric Wong
2010-06-21 19:03               ` Ryan Tomayko

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