update loaded middlewares and use of Rack::Server instead of Rack::Bu…

…ilder

guides/source/rails_on_rack.textile

@@ -27,25 +27,45 @@ h4. Rails Application's Rack Object
 
 h4. +rails server+
 
-<tt>rails server</tt> does the basic job of creating a +Rack::Builder+ object and starting the webserver. This is Rails' equivalent of Rack's +rackup+ script.
+<tt>rails server</tt> does the basic job of creating a +Rack::Server+ object and starting the webserver.
 
-Here's how +rails server+ creates an instance of +Rack::Builder+
+Here's how +rails server+ creates an instance of +Rack::Server+
 
 <ruby>
-app = Rack::Builder.new {
-  use Rails::Rack::LogTailer unless options[:detach]
-  use Rails::Rack::Debugger if options[:debugger]
-  use ActionDispatch::Static
-  run ApplicationName::Application
-}.to_app
+Rails::Server.new.tap { |server|
+  require APP_PATH
+  Dir.chdir(Rails.application.root)
+  server.start
+}
 </ruby>
 
-Middlewares used in the code above are primarily useful only in the development environment. The following table explains their usage:
+The +Rails::Server+ inherits from +Rack::Server+ and calls the +Rack::Server#start+ method this way:
+
+<ruby>
+class Server < ::Rack::Server
+  def start
+    ...
+    super
+  end
+end
+</ruby>
+
+Here's how it loads the middlewares:
+
+<ruby>
+def middleware
+  middlewares = []
+  middlewares << [Rails::Rack::Debugger]  if options[:debugger]
+  middlewares << [::Rack::ContentLength]
+  Hash.new(middlewares)
+end
+</ruby>
+
++Rails::Rack::Debugger+ is primarily useful only in the development environment. The following table explains the usage of the loaded middlewares:
 
 |_.Middleware|_.Purpose|
-|+Rails::Rack::LogTailer+|Appends log file output to console|
-|+ActionDispatch::Static+|Serves static files inside +Rails.root/public+ directory|
 |+Rails::Rack::Debugger+|Starts Debugger|
+|+Rack::ContentLength+|Counts the number of bytes in the response and set the HTTP Content-Length header|
 
 h4. +rackup+
 
@@ -55,8 +75,8 @@ To use +rackup+ instead of Rails' +rails server+, you can put the following insi
 # Rails.root/config.ru
 require "config/environment"
 
-use Rails::Rack::LogTailer
-use ActionDispatch::Static
+use Rack::Debugger
+use Rack::ContentLength
 run ApplicationName::Application
 </ruby>