shotgun man page

shotgun — reloading rack development server


shotgun [options] [rackup-file]


Shotgun is a simple process-per-request Rack server designed for use in development environments. Each time a request is received, shotgun forks, loads the rackup-file, processes a single request and exits. The result is application-wide reloading of all configuration, source files, and templates without the need for complex application-level reloading logic.

When no rackup-file is given, shotgun uses the file in the current working directory.


Shotgun runs at by default. The following options control server behavior:

-E, --env=environment

Sets the RACK_ENV environment variable to environment and selects the default set of utility middleware. When environment is ´development´, shotgun inserts the Rack::Lint and Rack::CommonLogger middleware components; when environment is ´production´ or ´deployed´, Rack::CommonLogger is inserted; otherwise, no utility middleware are inserted.

-P, --public=path

Serve requests for static files that exist under path from the shotgun master process without forking a worker process. This option is automatically enabled when a ./public directory is detected, but can be configured explicitly for non-conventional static file directory locations.

Setting this option appropriately can severely improve overall page load times for applications with many static assets.

-s, --server=mongrel|webrick|thin|other

The Rack server handler implementation used to serve requests. Supported values include: mongrel, webrick, and thin. By default, shotgun first tries to use mongrel and falls back to webrick if mongrel is not available.

-o, --host=addr

The hostname or address of the interface the HTTP server should bind to. Default:

-p, --port=port

The port the HTTP server should bind to. Default: 9393.

-O, --browse

Open browser at http://host:port/ immediately after the server is started.

Ruby environment related options:

-r, --require library

Require library before loading the application and starting the server. This can be used to load a portion of the application code in the master process so it doesn´t need to be loaded in the child. See Preloading][] for more information on this approach.

-e, --eval command

Evaluate arbitrary command within the shotgun master Ruby interpreter. command is evaluated as program arguments are parsed. Multiple -e arguments are allowed.

-d, --debug

Turns on debug mode. $DEBUG will be set true.

-w, --warn

Enable verbose mode without printing version message at the beginning. It sets the $VERBOSE variable to true.

-I, --include path

Add path to the Ruby load path ($LOAD_PATH). May be used more than once.


-h, --help

Show usage message and exit.


Show the Rack version and exit.


It´s possible to load support libraries and portions of the application in the shotgun master process to reduce the amount of work that needs to be done for each request in worker processes. There´s two ways of accomplishing this: either by specifying one or more --require (-r) arguments or through the use of a shotgun.rb file.

During start up, shotgun looks for a shotgun.rb or config/shotgun.rb file. If either file is found, it´s loaded into the shotgun master process. Code at the top-level of the shotgun.rb is run once on startup, so just require whatever you want to preload. It´s also possible to register callbacks to run before each request in either the master or child worker process:

after_fork { stuff }

Run stuff in the shotgun child worker process immediately after forking. Any files or socket connections opened in the master process should be closed / re-established by an after_fork block.

before_fork { stuff }

Run stuff in the shotgun master process on each request before forking the child worker process. This is typically less useful than after_fork, but provided for completeness.

Example config/shotgun.rb file from the main rails project:

# make sure the load path includes RAILS_ROOT
ENV[´RAILS_ROOT´] ||= File.expand_path(´../..´, __FILE__)
$:.unshift ENV[´RAILS_ROOT´]

# bring in the base rails environment and some libraries
require ´config/environment´
require ´google-charts´
require ´aws-s3´

# disable Rails´s built in class reloading
Rails.configuration.cache_classes = true

# reset database and redis connections in workers
after_fork do
  CHIMNEY.client = $redis


Shotgun is distributed as a gem package at
gem install shotgun

The rack package is required. The mongrel package is recommended.


Fork and report issues at
git clone git://

Version History

Version 0.9 (2011 February 24)

Version 0.8 (2010 June 24)

  • Preloading support. The shotgun.rb or config/shotgun.rb file is loaded at startup and may require libraries and register callbacks for fork events. See the section on Preloading.
  • Fix starting with the Thin handler (shotgun -s thin)
  • Actually include the shotgun(1) roff manual.

Version 0.7 (2010 June 22)

  • Static files now served from the shotgun master process, making shotgun tolerable for apps with many/unbundled static assets.
  • Added --public (-P) for specifying a non-standard root / public directory.
  • Response bodies are now streamed over the master < worker pipe instead of being marshalled. Improves performance with large response bodies, and reduces shotgun master process RES usage.
  • GET /favicon.ico requests are served an empty response by the shotgun master process. Prevents the need to fork a worker process.
  • INT, TERM, QUIT now properly trigger server shutdown. The second INT, TERM, QUIT causes the master process to exit hard.
  • Non .ru config files (e.g., sinatra app files) may now define command line options in the same way as .ru files: by including a #\ -p 5555 ... line.

Versions < 0.7 (2009-2010)

See Also



February 2011 Shotgun 0.9