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https://github.com/rack/rack

A modular Ruby web server interface.
https://github.com/rack/rack

rack ruby web

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A modular Ruby web server interface.

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README 

        
# ![Rack](contrib/logo.webp)



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 bridge between web servers, web

frameworks, and web application into a single method call.



The exact details of this are described in the [Rack Specification], which all

Rack applications should conform to.



## Version support



| Version  | Support                            |

|----------|------------------------------------|

|    3.1.x | Bug fixes and security patches.    |

|    3.0.x | Security patches only.             |

|    2.2.x | Security patches only.             |

| <= 2.1.x | End of support.                    |



Please see the [Security Policy] for more information.



## Rack 3.1



This is the latest version of Rack. It contains bug fixes and security patches.

Please check the [Change Log](CHANGELOG.md) for detailed information on specific

changes.



## Rack 3.0



This version of rack contains significant changes which are detailed in the

[Upgrade Guide](UPGRADE-GUIDE.md). It is recommended to upgrade to Rack 3 as soon

as possible to receive the latest features and security patches.



## Rack 2.2



This version of Rack is receiving security patches only, and effort should be

made to move to Rack 3.



Starting in Ruby 3.4 the `base64` dependency will no longer be a default gem,

and may cause a warning or error about `base64` being missing. To correct this,

add `base64` as a dependency to your project.



## Installation



Add the rack gem to your application bundle, or follow the instructions provided

by a [supported web framework](#supported-web-frameworks):



```bash

# Install it generally:

$ gem install rack



# or, add it to your current application gemfile:

$ bundle add rack

```



If you need features from `Rack::Session` or `bin/rackup` please add those gems separately.



```bash

$ gem install rack-session rackup

```



## Usage



Create a file called `config.ru` with the following contents:



```ruby

run do |env|

  [200, {}, ["Hello World"]]

end

```



Run this using the rackup gem or another [supported web

server](#supported-web-servers).



```bash

$ gem install rackup

$ rackup



# In another shell:

$ curl http://localhost:9292

Hello World

```



## Supported web servers



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



* [Agoo](https://github.com/ohler55/agoo)

* [Falcon](https://github.com/socketry/falcon)

* [Iodine](https://github.com/boazsegev/iodine)

* [NGINX Unit](https://unit.nginx.org/)

* [Phusion Passenger](https://www.phusionpassenger.com/) (which is mod_rack for

  Apache and for nginx)

* [Pitchfork](https://github.com/Shopify/pitchfork)

* [Puma](https://puma.io/)

* [Thin](https://github.com/macournoyer/thin)

* [Unicorn](https://yhbt.net/unicorn/)

* [uWSGI](https://uwsgi-docs.readthedocs.io/en/latest/)

* [Lamby](https://lamby.custominktech.com) (for AWS Lambda)



You will need to consult the server documentation to find out what features and

limitations they may have. In general, any valid Rack app will run the same on

all these servers, without changing anything.



### Rackup



Rack provides a separate gem, [rackup](https://github.com/rack/rackup) which is

a generic interface for running a Rack application on supported servers, which

include `WEBRick`, `Puma`, `Falcon` and others.



## Supported web frameworks



These frameworks and many others support the [Rack Specification]:



* [Camping](https://github.com/camping/camping)

* [Hanami](https://hanamirb.org/)

* [Ramaze](https://github.com/ramaze/ramaze)

* [Padrino](https://padrinorb.com/)

* [Roda](https://github.com/jeremyevans/roda)

* [Ruby on Rails](https://rubyonrails.org/)

* [Rum](https://github.com/leahneukirchen/rum)

* [Sinatra](https://sinatrarb.com/)

* [Utopia](https://github.com/socketry/utopia)

* [WABuR](https://github.com/ohler55/wabur)



## Available middleware shipped with Rack



Between the server and the framework, Rack can be customized to your

applications needs using middleware. Rack itself ships with the following

middleware:



* `Rack::CommonLogger` for creating Apache-style logfiles.

* `Rack::ConditionalGet` for returning [Not

  Modified](https://developer.mozilla.org/en-US/docs/Web/HTTP/Status/304)

  responses when the response has not changed.

* `Rack::Config` for modifying the environment before processing the request.

* `Rack::ContentLength` for setting a `content-length` header based on body

  size.

* `Rack::ContentType` for setting a default `content-type` header for responses.

* `Rack::Deflater` for compressing responses with gzip.

* `Rack::ETag` for setting `etag` header on bodies that can be buffered.

* `Rack::Events` for providing easy hooks when a request is received and when

  the response is sent.

* `Rack::Files` for serving static files.

* `Rack::Head` for returning an empty body for HEAD requests.

* `Rack::Lint` for checking conformance to the [Rack Specification].

* `Rack::Lock` for serializing requests using a mutex.

* `Rack::MethodOverride` for modifying the request method based on a submitted

  parameter.

* `Rack::Recursive` for including data from other paths in the application, and

  for 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 process

  the request.

* `Rack::Sendfile` for working with web servers that can use optimized file

  serving for file system paths.

* `Rack::ShowException` for catching unhandled exceptions and presenting them in

  a nice and helpful way with clickable backtrace.

* `Rack::ShowStatus` for using nice error pages for empty client error

  responses.

* `Rack::Static` for more 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 the

[Rack Specification]. These optional components can be used in any way you wish.



### Convenience interfaces



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.

* `Rack::Cascade` for trying additional Rack applications if an application

  returns a not found or method not supported response.

* `Rack::Directory` for serving files under a given directory, with directory

  indexes.

* `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 temporary

  file buffer.

* `Rack::URLMap` to route to multiple applications inside the same process.



## Configuration



Rack exposes several configuration parameters to control various features of the

implementation.



### `param_depth_limit`



```ruby

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.



### `multipart_file_limit`



```ruby

Rack::Utils.multipart_file_limit = 128 # default

```



The maximum number of parts with a filename a request can contain. Accepting

too 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 128

files at once. Set to 0 for no limit.



Can also be set via the `RACK_MULTIPART_FILE_LIMIT` environment variable.



(This is also aliased as `multipart_part_limit` and `RACK_MULTIPART_PART_LIMIT` for compatibility)



### `multipart_total_part_limit`



The maximum total number of parts a request can contain of any type, including

both file and non-file form fields.



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

4096 parts.



Set to 0 for no limit.



Can also be set via the `RACK_MULTIPART_TOTAL_PART_LIMIT` environment variable.



## Changelog



See [CHANGELOG.md](CHANGELOG.md).



## Contributing



See [CONTRIBUTING.md](CONTRIBUTING.md) for specific details about how to make a

contribution to Rack.



Please post bugs, suggestions and patches to [GitHub

Issues](https://github.com/rack/rack/issues).



Please check our [Security Policy](https://github.com/rack/rack/security/policy)

for responsible disclosure and security bug reporting process. Due to wide usage

of the library, it is strongly preferred that we manage timing in order to

provide viable patches at the time of disclosure. Your assistance in this matter

is greatly appreciated.



## See Also



### `rackup`



A useful tool for running Rack applications from the command line, including

`Rackup::Server` (previously `Rack::Server`) for scripting servers.



* https://github.com/rack/rackup



### `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.



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



### `rack-session`



Provides convenient session management for Rack.



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



## Thanks



The Rack Core Team, consisting of



* Aaron Patterson [tenderlove](https://github.com/tenderlove)

* Samuel Williams [ioquatix](https://github.com/ioquatix)

* Jeremy Evans [jeremyevans](https://github.com/jeremyevans)

* Eileen Uchitelle [eileencodes](https://github.com/eileencodes)

* Matthew Draper [matthewd](https://github.com/matthewd)

* Rafael França [rafaelfranca](https://github.com/rafaelfranca)



and the Rack Alumni



* Ryan Tomayko [rtomayko](https://github.com/rtomayko)

* Scytrin dai Kinthra [scytrin](https://github.com/scytrin)

* Leah Neukirchen [leahneukirchen](https://github.com/leahneukirchen)

* James Tucker [raggi](https://github.com/raggi)

* Josh Peek [josh](https://github.com/josh)

* José Valim [josevalim](https://github.com/josevalim)

* Michael Fellinger [manveru](https://github.com/manveru)

* Santiago Pastorino [spastorino](https://github.com/spastorino)

* Konstantin Haase [rkh](https://github.com/rkh)



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.

* Alex Beregszaszi, Alexander Kahn, Anil Wadghule, Aredridel, Ben Alpert, Dan

  Kubb, Daniel Roethlisberger, Matt Todd, Tom Robinson, Phil Hagelberg, S. Brent

  Faulkner, Bosko Milekic, Daniel Rodríguez Troitiño, Genki Takiuchi, Geoffrey

  Grosenbach, Julien Sanchez, Kamal Fariz Mahyuddin, Masayoshi Takahashi,

  Patrick Aljordm, Mig, Kazuhiro Nishiyama, Jon Bardin, Konstantin Haase, Larry

  Siden, 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 API

  improvements.

* Yehuda Katz and Carl Lerche for refactoring rackup.

* 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 contributors not mentioned above.



## License



Rack is released under the [MIT License](MIT-LICENSE).



[Rack Specification]: SPEC.rdoc

[Security Policy]: SECURITY.md