This is an automatic reloading version of the rackup command that's shipped with Rack. It can be used as an alternative to the complex reloading logic provided by web frameworks or in environments that don't support application reloading.
The shotgun command starts one of Rack's supported servers (e.g., mongrel, thin, webrick) and listens for requests but does not load any part of the actual application. Each time a request is received, it forks, loads the application in the child process, processes the request, and exits the child process. The result is clean, application-wide reloading of all source files and templates on each request.
gem install shotgun
Starting a server with a rackup file:
Using Thin and starting on port 6000 instead of 9393 (default):
shotgun --server=thin --port=6000 config.ru
Running Sinatra apps:
See 'shotgun --help' for more advanced usage.
The reloading system in Ian Bicking's webware framework served as inspiration for the approach taken in Shotgun. Ian lays down the pros and cons of this approach in the following article: