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= Rack, a modular Ruby webserver interface
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.
== Specification changes in this release
With Rack 1.0, the Rack specification (found in SPEC) changed in the
following backward-incompatible ways. This was done to properly
support Ruby 1.9 and to deprecate some problematic techniques:
* Rack::VERSION has been pushed to [1,0].
* Header values must be Strings now, split on "\n".
* rack.input must be rewindable and support reading into a buffer,
wrap with Rack::RewindableInput if it isn't.
* Content-Length can be missing, in this case chunked transfer
encoding is used.
* Bodies can now additionally respond to #to_path with a filename to
be served.
* String bodies are deprecated and will not work with Ruby 1.9, use an
Array with a single String instead.
* rack.session is now specified.
== Supported web servers
The included *handlers* connect all kinds of web servers to Rack:
* Mongrel
* EventedMongrel
* SwiftipliedMongrel
* WEBrick
* LiteSpeed
* Thin
These web servers include Rack handlers in their distributions:
* Ebb
* Fuzed
* Phusion Passenger (which is mod_rack for Apache and for nginx)
* Unicorn
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
These frameworks include Rack adapters in their distributions:
* Camping
* Coset
* Halcyon
* Mack
* Maveric
* Merb
* Racktools::SimpleApplication
* Ramaze
* Ruby on Rails
* Rum
* Sinatra
* Sin
* Vintage
* Waves
* Wee
Current links to these projects can be found at
== 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.
* ...many others!
All these components use the same interface, which is described in
detail in the Rack specification. These optional components can be
used in any way you wish.
== Convenience
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
* 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.
== rack-contrib
The plethora of useful middleware created the need for a project that
collects fresh Rack middleware. rack-contrib includes a variety of
add-on components for Rack and it is easy to contribute new modules.
== rackup
rackup is a useful tool for running Rack applications, which uses the
Rack::Builder DSL to configure middleware and build up applications
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.
== Quick start
Try the lobster!
Either with the embedded WEBrick starter:
ruby -Ilib lib/rack/lobster.rb
Or with rackup:
bin/rackup -Ilib example/
By default, the lobster is found at http://localhost:9292.
== 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
== Running the tests
Testing Rack requires the test/spec testing framework:
gem install test-spec
There are two rake-based test tasks:
rake test tests all the fast tests (no Handlers or Adapters)
rake fulltest runs all the tests
The fast testsuite has no dependencies outside of the core Ruby
installation and test-spec.
To run the test suite completely, you need:
* camping
* fcgi
* memcache-client
* mongrel
* ruby-openid
* thin
The full set of tests test FCGI access with lighttpd (on port
9203) so you will need lighttpd installed as well as the FCGI
libraries and the fcgi gem:
Download and install lighttpd:
Installing the FCGI libraries:
curl -O
tar xzvf fcgi-2.4.0.tar.gz
cd fcgi-2.4.0
./configure --prefix=/usr/local
sudo make install
cd ..
Installing the Ruby fcgi gem:
gem install fcgi
Furthermore, to test Memcache sessions, you need memcached (will be
run on port 11211) and memcache-client installed.
== History
* March 3rd, 2007: First public release 0.1.
* May 16th, 2007: Second public release 0.2.
* HTTP Basic authentication.
* Cookie Sessions.
* Static file handler.
* Improved Rack::Request.
* Improved Rack::Response.
* Added Rack::ShowStatus, for better default error messages.
* Bug fixes in the Camping adapter.
* Removed Rails adapter, was too alpha.
* February 26th, 2008: Third public release 0.3.
* LiteSpeed handler, by Adrian Madrid.
* SCGI handler, by Jeremy Evans.
* Pool sessions, by blink.
* OpenID authentication, by blink.
* :Port and :File options for opening FastCGI sockets, by blink.
* Last-Modified HTTP header for Rack::File, by blink.
* Rack::Builder#use now accepts blocks, by Corey Jewett.
(See example/
* HTTP status 201 can contain a Content-Type and a body now.
* Many bugfixes, especially related to Cookie handling.
* August 21st, 2008: Fourth public release 0.4.
* New middleware, Rack::Deflater, by Christoffer Sawicki.
* OpenID authentication now needs ruby-openid 2.
* New Memcache sessions, by blink.
* Explicit EventedMongrel handler, by Joshua Peek <>
* Rack::Reloader is not loaded in rackup development mode.
* rackup can daemonize with -D.
* Many bugfixes, especially for pool sessions, URLMap, thread safety
and tempfile handling.
* Improved tests.
* Rack moved to Git.
* January 6th, 2009: Fifth public release 0.9.
* Rack is now managed by the Rack Core Team.
* Rack::Lint is stricter and follows the HTTP RFCs more closely.
* Added ConditionalGet middleware.
* Added ContentLength middleware.
* Added Deflater middleware.
* Added Head middleware.
* Added MethodOverride middleware.
* Rack::Mime now provides popular MIME-types and their extension.
* Mongrel Header now streams.
* Added Thin handler.
* Official support for swiftiplied Mongrel.
* Secure cookies.
* Made HeaderHash case-preserving.
* Many bugfixes and small improvements.
* January 9th, 2009: Sixth public release 0.9.1.
* Fix directory traversal exploits in Rack::File and Rack::Directory.
* April 25th, 2009: Seventh public release 1.0.0.
* SPEC change: Rack::VERSION has been pushed to [1,0].
* SPEC change: header values must be Strings now, split on "\n".
* SPEC change: Content-Length can be missing, in this case chunked transfer
encoding is used.
* SPEC change: rack.input must be rewindable and support reading into
a buffer, wrap with Rack::RewindableInput if it isn't.
* SPEC change: rack.session is now specified.
* SPEC change: Bodies can now additionally respond to #to_path with
a filename to be served.
* NOTE: String bodies break in 1.9, use an Array consisting of a
single String instead.
* New middleware Rack::Lock.
* New middleware Rack::ContentType.
* Rack::Reloader has been rewritten.
* Major update to Rack::Auth::OpenID.
* Support for nested parameter parsing in Rack::Response.
* Support for redirects in Rack::Response.
* HttpOnly cookie support in Rack::Response.
* The Rakefile has been rewritten.
* Many bugfixes and small improvements.
* October 18th, 2009: Eighth public release 1.0.1.
* Bump remainder of rack.versions.
* Support the pure Ruby FCGI implementation.
* Fix for form names containing "=": split first then unescape components
* Fixes the handling of the filename parameter with semicolons in names.
* Add anchor to nested params parsing regexp to prevent stack overflows
* Use more compatible gzip write api instead of "<<".
* Make sure that Reloader doesn't break when executed via ruby -e
* Make sure WEBrick respects the :Host option
* Many Ruby 1.9 fixes.
== Contact
Please mail bugs, suggestions and patches to
Mailing list archives are available at
There is a bug tracker at <>.
Git repository (send Git patches to the mailing list):
You are also welcome to join the #rack channel on
== Thanks
The Rack Core Team, consisting of
* Christian Neukirchen (chneukirchen)
* James Tucker (raggi)
* Josh Peek (josh)
* Michael Fellinger (manveru)
* Ryan Tomayko (rtomayko)
* Scytrin dai Kinthra (scytrin)
would like to thank:
* Adrian Madrid, for the LiteSpeed handler.
* Christoffer Sawicki, for the first Rails adapter and Rack::Deflater.
* Tim Fletcher, for the HTTP authentication code.
* Luc Heinrich for the Cookie sessions, the static file handler and bugfixes.
* Armin Ronacher, for the logo and racktools.
* Aredridel, Ben Alpert, Dan Kubb, Daniel Roethlisberger, Matt Todd,
Tom Robinson, Phil Hagelberg, and S. Brent Faulkner for bug fixing
and other improvements.
* Brian Candler, for Rack::ContentType.
* Graham Batty, for improved handler loading.
* Stephen Bannasch, for bug reports and documentation.
* Gary Wright, for proposing a better Rack::Response interface.
* Jonathan Buch, for improvements regarding Rack::Response.
* Armin Röhrl, for tracking down bugs in the Cookie generator.
* Alexander Kellett for testing the Gem and reviewing the announcement.
* 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.
* All bug reporters and patch contributers not mentioned above.
== Copyright
Copyright (C) 2007, 2008, 2009 Christian Neukirchen <>
Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to
deal in the Software without restriction, including without limitation the
rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
sell copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:
The above copyright notice and this permission notice shall be included in
all copies or substantial portions of the Software.
== Links
Rack:: <>
Rack's Rubyforge project:: <>
Official Rack repositories:: <>
rack-devel mailing list:: <>
Christian Neukirchen:: <>