Unicorn: UNIX + LAN/localhost-only fork of Mongrel

Only run this behind a full-HTTP-request-buffering reverse proxy if you’re serving slow clients. That said, nginx is the only reverse proxy we know of that meets this requirement.

Features

• process management: Unicorn will reap and restart workers that die because of broken apps and there is no need to manage multiple processes yourself.
• does not care if your application is thread-safe or not, workers all run within their own isolated address space and only serve one client at a time…
• able to listen on multiple interfaces, including UNIX sockets, each worker process can also bind to a private port via the after_fork hook for easy debugging.
• supports all Rack applications
• nginx-style binary re-execution without losing connections. You can upgrade unicorn, your entire application, libraries and even your Ruby interpreter as long as unicorn is installed in the same path.
• before_fork and after_fork hooks in case your application has special needs when dealing with forked processes.
• builtin log rotation via USR1 signal
• Ruby 1.9-compatible (at least the test cases all pass :>)

License

Unicorn is copyright 2009 Eric Wong and contributors. It is based on Mongrel and carries the same license:

Mongrel is copyright 2007 Zed A. Shaw and contributors. It is licensed under the Ruby license and the GPL2. See the include LICENSE file for details.

Install

The library consists of a C extension so you’ll need a C compiler or at least a friend who can build it for you.

You may download the tarball from the Mongrel project page on Rubyforge and run setup.rb after unpacking it:

rubyforge.org/frs/?group_id=1306

You may also install it via Rubygems on Rubyforge:

  gem install unicorn

You can get the latest source via git from the following locations (these versions may not be stable):

  git://git.bogomips.org/unicorn.git
  http://git.bogomips.org/unicorn.git
  git://repo.or.cz/unicorn.git (mirror)
  http://repo.or.cz/r/unicorn.git (mirror)

If you have web browser software for the World Wide Web (on the Information Superhighway), you may browse the code from your web browser and download the latest snapshot tarballs here:

• git.bogomips.org/cgit/unicorn.git
• repo.or.cz/w/unicorn.git (gitweb mirror)

Usage

non-Rails Rack applications

Unicorn will look for the config.ru file used by rackup in APP_ROOT. Optionally, it can use a config file for unicorn-specific options specified by the —config-file/-c command-line switch. See Unicorn::Configurator for the syntax of the unicorn-specific config options.

In APP_ROOT, just run:

  unicorn

Unicorn should be capable of running most Rack applications. Since this is a preforking webserver, you do not have to worry about thread-safety of your application or libraries. However, your Rack application may use threads internally (and should even be able to continue running threads after the request is complete).

Rack-enabled versions of Rails (v2.3.2+)

In RAILS_ROOT, run:

  unicorn_rails

Most command-line options for other Rack applications (above) are also supported. The unicorn_rails launcher attempts to combine the best features of the Rails-bundled "script/server" with the "rackup"-like functionality of the `unicorn’ launcher.

Disclaimer

There are no known production instances of unicorn deployed anywhere in the world. The original author of unicorn only has one, internal, low-traffic Sinatra application deployed with it. Maybe you’ll be the first guinea pig to test it in production. Of course there is NO WARRANTY whatsoever if anything goes wrong, but let us know and we’ll try our best to fix it.

Known Issues

• WONTFIX: code reloading with Sinatra 0.3.2 (and likely older versions) apps is broken. The workaround is to force production mode to disable code reloading in your Sinatra application:

    set :env, :production
  

  Since this is no longer an issue with Sinatra 0.9.x apps and only affected non-production instances, this will not be fixed on our end. Also remember we’re capable of replacing the running binary without dropping any connections regardless of framework :)

Contact

Newsgroup and mailing list maybe coming… Email Eric Wong at normalperson@yhbt.net for now.