Logging errors from Unicorn

Peter Kieltyka peter.kieltyka at nulayer.com
Fri Jun 4 15:06:17 EDT 2010

Hey guys,

I'm running a Rails 3 beta3 application using Ruby 1.9.2-preview3 and it has been running fairly well, however every now and then (usually when under high load), I see error messages like:

2010/06/04 14:34:29 [error] 1884#0: *8844 upstream prematurely closed connection while reading response header from upstream, client:, server: portal.crowdreel.com, request: "GET /post/18Vmy HTTP/1.1", upstream: "http://unix:/home/app/crowdreel-portal/tmp/sockets/unicorn.sock:/post/18Vmy", host: "crowdreel.com"

... a lot of these messages.. this is a pretty heavy duty server with lots of ram.

I have a setup similar to what I read up on github's blog as in: nginx -> unicorns via a socket upstream.

My unicorn.rb file looks like:


# 16 workers and 1 master
worker_processes 16

# Load the app into the master before forking workers for super-fast worker spawn times
preload_app false

# Restart any workers that haven't responded in 30 seconds
timeout 45

# Listen on a Unix data socket
listen File.expand_path(File.dirname(__FILE__)+'/../tmp/sockets/unicorn.sock'), :backlog => 2048


I don't preload the app because I start running into annoying issues where my workers use the same db connection, so instead I just have them load their own instance, its very fast to start up anyways.

I've read everything I could on this issue and exhausted Google, which leaves me to think the only thing left is some incompatibilities with 1.9.2. So I was wondering, how can I get logs from unicorn's workers/master to know what is happening to these workers, perhaps something is segfaulting?




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