Rails Metal applications are minimal Rack applications specially designed for integrating with a typical Rails application. As Rails Metal Applications skip all of the Action Controller stack, serving a request has no overhead from the Rails framework itself. This is especially useful for infrequent cases where the performance of the full stack Rails framework is an issue.
+Ryan Bates' railscast on the "Rails Metal":http://railscasts.com/episodes/150-rails-metal provides a nice walkthrough generating and using Rails Metal.
h4. Generating a Metal Application
Rails provides a generator called +metal+ for creating a new Metal application:
@@ -286,6 +288,19 @@ Each string in the array should be the name of your metal class. If you do this
WARNING: Metal applications cannot return the HTTP Status +404+ to a client, as it is used for continuing the Metal chain execution. Please use normal Rails controllers or a custom middleware if returning +404+ is a requirement.