leah blogs

March 2007

03mar2007 · Rack 0.1, a modular Ruby webserver interface

Today I’m proud to release Rack 0.1.

Rack provides a minimal, modular and adaptable interface for developing web applications in Ruby. By wrapping HTTP requests and responses in the simplest way possible, it unifies and distills the API for web servers, web frameworks, and software in between (the so-called middleware) into a single method call.

The exact details of this are described in the Rack specification, which all Rack applications should conform to.

Supported web servers

The included handlers connect all kinds of web servers to Rack:

  • Mongrel
  • WEBrick
  • FCGI
  • CGI

Any valid Rack app will run the same on all these handlers, without changing anything.

Supported web frameworks

The included adapters connect Rack with existing Ruby web frameworks:

  • Camping
  • Rails (alpha)
  • more to come soon, …

These frameworks include Rack adapters in their distributions:

  • Ramaze
  • Maveric
  • Racktools::SimpleApplication

Available middleware

Between the server and the framework, Rack can be customized to your applications needs using middleware, for example:

  • Rack::URLMap, to route to multiple applications inside the same process.
  • Rack::CommonLogger, for creating Apache-style logfiles.
  • Rack::ShowException, for catching unhandled exceptions and presenting them in a nice and helpful way with clickable backtrace.
  • Rack::File, for serving static files.

All these components use the same interface, which is described in detail in the Rack specification. You can choose to use them exactly in the way you want.


If you want to develop outside of existing frameworks, implement your own ones, or develop middleware, Rack provides many helpers to create Rack applications quickly and without doing the same web stuff all over:

  • Rack::Request, which also provides query string parsing and multipart handling.
  • Rack::Response, for convenient generation of HTTP replies and cookie handling.
  • Rack::MockRequest and Rack::MockResponse for efficient and quick testing of Rack application without real HTTP round-trips.


rackup is a useful tool for running Rack applications, which uses the Rack::Builder DSL to configure middleware and build up applications easily.

rackup automatically figures out the environment it is run in, and runs your application as FastCGI, CGI, or standalone with Mongrel or WEBrick—all from the same configuration.

Where can I get it?

You can download Rack 0.1 here:

Alternatively, you can checkout from the development repository with:

darcs get http://chneukirchen.org/repos/rack

(Patches using “darcs send” are most welcome.)

Installing with RubyGems

A Gem of Rack is available. You can install it with:

gem install rack

I also provide a local mirror of the gems (and development snapshots) at my site:

gem install rack --source http://chneukirchen.org/releases/gems


Please mail bugs, suggestions and patches to .

You are also welcome to join the #rack channel on irc.freenode.net.

Thanks to

  • Michael Fellinger, for helpful discussion.
  • Christoffer Sawicki, for the Rails adapter.
  • Armin Ronacher, for the logo and racktools.
  • Marcus Rückert, for help with configuring and debugging lighttpd.
  • The WSGI team for the well-done and documented work they’ve done and Rack builds up on.


Copyright (C) 2007 Christian Neukirchen http://purl.org/net/chneukirchen

Rack is freely distributable under the terms of an MIT-style license.


Rack: http://rack.rubyforge.org/
Rack’s Rubyforge project: http://rubyforge.org/projects/rack

Camping: http://camping.rubyforge.org/
Ramaze: http://ramaze.rubyforge.org/
Maveric: http://maveric.rubyforge.org/
racktools: http://lucumr.pocoo.org/trac/repos/racktools/

79b46158b7b30adcd7a9148cc7ed4305  rack-0.1.0.tar.gz
61a51b2f609833f4e0c11213a0070721  rack-0.1.0.gem

NP: Tom Waits—Take Care Of All My Children

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