Make generated Metal bits a pure rack endpoint application (not middleware)

Instead of calling super to pass the request on, return a 404.
The modified app looks like this:

  # app/metal/poller.rb
  class Poller
    def self.call(env)
      if env["PATH_INFO"] =~ /^\/poller/
        [200, {"Content-Type" => "text/html"}, "Hello, World!"]
      else
        [404, {"Content-Type" => "text/html"}, "Not Found"]
      end
    end
  end

But you aren't locked in to just Rails:

  # app/metal/api.rb
  require 'sinatra'
  Sinatra::Application.default_options.merge!(:run => false, :env => :production)
  Api = Sinatra.application unless defined? Api

  get '/interesting/new/ideas' do
    'Hello Sinatra!'
  end

1 files changed, 8 insertions, 12 deletions

diff --git a/railties/lib/rails/rack/metal.rb b/railties/lib/rails/rack/metal.rb
index 8dfbedad90..77d00ab091 100644
--- a/railties/lib/rails/rack/metal.rb
+++ b/railties/lib/rails/rack/metal.rb
@@ -1,21 +1,17 @@
 module Rails
   module Rack
     class Metal
+      def self.new(app)
+        apps = Dir["#{Rails.root}/app/metal/*.rb"].map do |file|
+          File.basename(file, '.rb').camelize.constantize
+        end
+        apps << app
+        ::Rack::Cascade.new(apps)
+      end
+
       NotFound = lambda { |env|
         [404, {"Content-Type" => "text/html"}, "Not Found"]
       }
-
-      def self.call(env)
-        new(NotFound).call(env)
-      end
-
-      def initialize(app)
-        @app = app
-      end
-
-      def call(env)
-        @app.call(env)
-      end
     end
   end
 end