Repository files navigation

Rack provides a minimal, modular, and adaptable interface for developing webapplications in Ruby. By wrapping HTTP requests and responses in the simplestway possible, it unifies and distills the bridge between web servers, webframeworks, and web application into a single method call.

The exact details of this are described in theRack Specification, which allRack applications should conform to. Browse theDocumentation for moreinformation.

Please see theSecurity Policy for more information.

This is the latest version of Rack. It contains bug fixes and security patches.Please check theChange Log for detailed information on specificchanges.

This version of rack contains significant changes which are detailed in theUpgrade Guide. It is recommended to upgrade to Rack 3 as soonas possible to receive the latest features and security patches.

This version of Rack is receiving security patches only, and effort should bemade to move to Rack 3.

Starting in Ruby 3.4 thebase64 dependency will no longer be a default gem,and may cause a warning or error aboutbase64 being missing. To correct this,addbase64 as a dependency to your project.

Add the rack gem to your application bundle, or follow the instructions providedby asupported web framework:

# Install it generally:$ gem install rack# or, add it to your current application gemfile:$ bundle add rack

If you need features fromRack::Session orbin/rackup please add those gems separately.

$ gem install rack-session rackup

Create a file calledconfig.ru with the following contents:

rundo |env|[200,{},["Hello World"]]end

Run this using the rackup gem or anothersupported webserver.

$ gem install rackup$ rackup# In another shell:$ curl http://localhost:9292Hello World

Rack is supported by a wide range of servers, including:

• Agoo
• Falcon
• Iodine
• NGINX Unit
• Phusion Passenger (which is mod_rack forApache and for nginx)
• Pitchfork
• Puma
• Thin
• Unicorn
• uWSGI
• Lamby (for AWS Lambda)

You will need to consult the server documentation to find out what features andlimitations they may have. In general, any valid Rack app will run the same onall these servers, without changing anything.

Rack provides a separate gem,rackup which isa generic interface for running a Rack application on supported servers, whichincludeWEBRick,Puma,Falcon and others.

These frameworks and many others support theRack Specification:

• Camping
• Hanami
• Ramaze
• Padrino
• Roda
• Ruby on Rails
• Rum
• Sinatra
• Utopia
• WABuR

Between the server and the framework, Rack can be customized to yourapplications needs using middleware. Rack itself ships with the followingmiddleware:

• Rack::CommonLogger for creating Apache-style logfiles.
• Rack::ConditionalGet for returningNotModifiedresponses when the response has not changed.
• Rack::Config for modifying the environment before processing the request.
• Rack::ContentLength for setting acontent-length header based on bodysize.
• Rack::ContentType for setting a defaultcontent-type header for responses.
• Rack::Deflater for compressing responses with gzip.
• Rack::ETag for settingetag header on bodies that can be buffered.
• Rack::Events for providing easy hooks when a request is received and whenthe response is sent.
• Rack::Head for returning an empty body for HEAD requests.
• Rack::Lint for checking conformance to theRack Specification.
• Rack::Lock for serializing requests using a mutex.
• Rack::MethodOverride for modifying the request method based on a submittedparameter.
• Rack::Recursive for including data from other paths in the application, andfor performing internal redirects.
• Rack::Reloader for reloading files if they have been modified.
• Rack::Runtime for including a response header with the time taken to processthe request.
• Rack::Sendfile for working with web servers that can use optimized fileserving for file system paths.
• Rack::ShowException for catching unhandled exceptions and presenting them ina nice and helpful way with clickable backtrace.
• Rack::ShowStatus for using nice error pages for empty client errorresponses.
• Rack::Static for configurable serving of static files.
• Rack::TempfileReaper for removing temporary files creating during a request.

All these components use the same interface, which is described in detail in theRack Specification. These optional components can be used in any way you wish.

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

• Rack::Request which also provides query string parsing and multiparthandling.
• Rack::Response for convenient generation of HTTP replies and cookiehandling.
• Rack::MockRequest andRack::MockResponse for efficient and quick testingof Rack application without real HTTP round-trips.
• Rack::Cascade for trying additional Rack applications if an applicationreturns a not found or method not supported response.
• Rack::Directory for serving files under a given directory, with directoryindexes.
• Rack::Files for serving files under a given directory, without directoryindexes.
• Rack::MediaType for parsing content-type headers.
• Rack::Mime for determining content-type based on file extension.
• Rack::RewindableInput for making any IO object rewindable, using a temporaryfile buffer.
• Rack::URLMap to route to multiple applications inside the same process.

Rack exposes several configuration parameters to control various features of theimplementation.

This environment variable sets the default for the maximum query string bytesizethatRack::QueryParser will attempt to parse. Attempts to use a query stringthat exceeds this number of bytes will result in aRack::QueryParser::QueryLimitError exception. If this enviroment variable isprovided, it must be an integer, orRack::QueryParser will raise an exception.

The default limit can be overridden on a per-Rack::QueryParser basis usingthebytesize_limit keyword argument when creating theRack::QueryParser.

This environment variable sets the default for the maximum number of queryparameters thatRack::QueryParser will attempt to parse. Attempts to use aquery string with more than this many query parameters will result in aRack::QueryParser::QueryLimitError exception. If this enviroment variable isprovided, it must be an integer, orRack::QueryParser will raise an exception.

The default limit can be overridden on a per-Rack::QueryParser basis usingtheparams_limit keyword argument when creating theRack::QueryParser.

This is implemented by counting the number of parameter separators in thequery string, before attempting parsing, so if the same parameter key isused multiple times in the query, each counts as a separate parameter forthis check.

Rack::Utils.param_depth_limit=32# default

The maximum amount of nesting allowed in parameters. For example, if set to 3,this query string would be allowed:

?a[b][c]=d

but this query string would not be allowed:

?a[b][c][d]=e

Limiting the depth prevents a possible stack overflow when parsing parameters.

Rack::Utils.multipart_file_limit=128# default

The maximum number of parts with a filename a request can contain. Acceptingtoo many parts can lead to the server running out of file handles.

The default is 128, which means that a single request can't upload more than 128files at once. Set to 0 for no limit.

Can also be set via theRACK_MULTIPART_FILE_LIMIT environment variable.

(This is also aliased asmultipart_part_limit andRACK_MULTIPART_PART_LIMIT for compatibility)

The maximum total number of parts a request can contain of any type, includingboth file and non-file form fields.

The default is 4096, which means that a single request can't contain more than4096 parts.

Set to 0 for no limit.

Can also be set via theRACK_MULTIPART_TOTAL_PART_LIMIT environment variable.

SeeCHANGELOG.md.

SeeCONTRIBUTING.md for specific details about how to make acontribution to Rack.

Please post bugs, suggestions and patches toGitHubIssues.

Please check ourSecurity Policyfor responsible disclosure and security bug reporting process. Due to wide usageof the library, it is strongly preferred that we manage timing in order toprovide viable patches at the time of disclosure. Your assistance in this matteris greatly appreciated.

A useful tool for running Rack applications from the command line, includingRackup::Server (previouslyRack::Server) for scripting servers.

• https://github.com/rack/rackup

The plethora of useful middleware created the need for a project that collectsfresh Rack middleware.rack-contrib includes a variety of add-on componentsfor Rack and it is easy to contribute new modules.

• https://github.com/rack/rack-contrib

Provides convenient session management for Rack.

• https://github.com/rack/rack-session

The Rack Core Team, consisting of

• Aaron Pattersontenderlove
• Samuel Williamsioquatix
• Jeremy Evansjeremyevans
• Eileen Uchitelleeileencodes
• Matthew Drapermatthewd
• Rafael Françarafaelfranca

and the Rack Alumni

• Ryan Tomaykortomayko
• Scytrin dai Kinthrascytrin
• Leah Neukirchenleahneukirchen
• James Tuckerraggi
• Josh Peekjosh
• José Valimjosevalim
• Michael Fellingermanveru
• Santiago Pastorinospastorino
• Konstantin Haaserkh

would like to thank:

• Adrian Madrid, for the LiteSpeed handler.
• Christoffer Sawicki, for the first Rails adapter andRack::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.
• Alex Beregszaszi, Alexander Kahn, Anil Wadghule, Aredridel, Ben Alpert, DanKubb, Daniel Roethlisberger, Matt Todd, Tom Robinson, Phil Hagelberg, S. BrentFaulkner, Bosko Milekic, Daniel Rodríguez Troitiño, Genki Takiuchi, GeoffreyGrosenbach, Julien Sanchez, Kamal Fariz Mahyuddin, Masayoshi Takahashi,Patrick Aljordm, Mig, Kazuhiro Nishiyama, Jon Bardin, Konstantin Haase, LarrySiden, Matias Korhonen, Sam Ruby, Simon Chiang, Tim Connor, Timur Batyrshin,and Zach Brock for bug fixing and other improvements.
• Eric Wong, Hongli Lai, Jeremy Kemper for their continuous support and APIimprovements.
• Yehuda Katz and Carl Lerche for refactoring rackup.
• Brian Candler, forRack::ContentType.
• Graham Batty, for improved handler loading.
• Stephen Bannasch, for bug reports and documentation.
• Gary Wright, for proposing a betterRack::Response interface.
• Jonathan Buch, for improvements regardingRack::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 Rackbuilds up on.
• All bug reporters and patch contributors not mentioned above.

Rack is released under theMIT License.