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From: "Iñaki Baz Castillo" <ibc@aliax.net>
To: mongrel-unicorn@rubyforge.org
Subject: Re: Strange Thread related errors
Date: Thu, 7 Jan 2010 17:31:49 +0100	[thread overview]
Message-ID: <201001071731.49847.ibc@aliax.net> (raw)
In-Reply-To: <944a03771001070805k27356c9dwdc535bed8efa7bb6@mail.gmail.com>

El Jueves, 7 de Enero de 2010, Michael Guterl escribió:
> Our Rails app has started raising exceptions (caught by hoptoad
> thankfully) and I can only imagine they're related to unicorn.  I only
> think the errors are occurring on the request after we deploy, which
> upgrades the Unicorn process.  I say this because the errors are
> coming from many different actions, but I haven't been able to
> reproduce.

Let me explain a problem I had with Sequel and Unicorn (already solved), 
perhaps it's related:

I load Sequel database toolkit in the master process so it generates its own 
threads pool.
Then Unicorn forks into workers but each worker uses the same instance of 
Sequel database, this is, the same threads pool.

This causes errors since some thread could be used by different processes at 
the same time.

The solution is simple:

Don't set the Sequel instance in the master process, instead do it in each 
worker ("after_fork" block in unicorn config file).

In this way each process has its own Sequel instance with its own threads 

Also, using Sequel thread pool makes no sense when using Unicorn as each 
worker is single thread, so I gain some performance by setting 
"single_threaded = true" in Sequel database configuration (no thread pool 

Probably you are getting a similar issue due to ActiveRecord or any other 
multithread library you load in the master process so the instance is shared 
between all the workers.

Iñaki Baz Castillo <ibc@aliax.net>
Unicorn mailing list - mongrel-unicorn@rubyforge.org
Do not quote signatures (like this one) or top post when replying

  reply	other threads:[~2010-01-07 16:32 UTC|newest]

Thread overview: 9+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2010-01-07 16:05 Strange Thread related errors Michael Guterl
2010-01-07 16:31 ` Iñaki Baz Castillo [this message]
2010-01-07 18:10   ` Jeremy Evans
2010-01-07 18:33     ` Iñaki Baz Castillo
2010-01-07 18:49   ` Michael Guterl
2010-01-07 19:08     ` Iñaki Baz Castillo
2010-01-07 20:08     ` Jeremy Evans
2010-01-07 20:13 ` Eric Wong
2010-01-07 21:32   ` Michael Guterl

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