Move gaint lock into middleware

actionpack/lib/action_controller.rb

@@ -56,6 +56,7 @@ module ActionController
   autoload :Integration, 'action_controller/integration'
   autoload :IntegrationTest, 'action_controller/integration'
   autoload :Layout, 'action_controller/layout'
+  autoload :Lock, 'action_controller/lock'
   autoload :MiddlewareStack, 'action_controller/middleware_stack'
   autoload :MimeResponds, 'action_controller/mime_responds'
   autoload :PolymorphicRoutes, 'action_controller/polymorphic_routes'

actionpack/lib/action_controller/dispatcher.rb

@@ -2,8 +2,6 @@ module ActionController
   # Dispatches requests to the appropriate controller and takes care of
   # reloading the app after each request when Dependencies.load? is true.
   class Dispatcher
-    @@guard = Mutex.new
-
     class << self
       def define_dispatcher_callbacks(cache_classes)
         unless cache_classes
@@ -46,6 +44,7 @@ module ActionController
 
     cattr_accessor :middleware
     self.middleware = MiddlewareStack.new do |middleware|
+      middleware.use "ActionController::Lock", :if => lambda { !ActionController::Base.allow_concurrency }
       middleware.use "ActionController::Failsafe"
       middleware.use "ActionController::SessionManagement::Middleware"
     end
@@ -59,7 +58,7 @@ module ActionController
       @app = @@middleware.build(lambda { |env| self.dup._call(env) })
     end
 
-    def dispatch_unlocked
+    def dispatch
       begin
         run_callbacks :before_dispatch
         handle_request
@@ -70,16 +69,6 @@ module ActionController
       end
     end
 
-    def dispatch
-      if ActionController::Base.allow_concurrency
-        dispatch_unlocked
-      else
-        @@guard.synchronize do
-          dispatch_unlocked
-        end
-      end
-    end
-
     # DEPRECATE: Remove CGI support
     def dispatch_cgi(cgi, session_options)
       CGIHandler.dispatch_cgi(self, cgi, @output)

actionpack/lib/action_controller/lock.rb

@@ -0,0 +1,18 @@
+module ActionController
+  class Lock
+    def initialize(app)
+      @app = app
+      @lock = Mutex.new
+    end
+
+    def call(env)
+      old_multithread = env["rack.multithread"]
+      env["rack.multithread"] = false
+      response = @lock.synchronize do
+        @app.call(env)
+      end
+      env["rack.multithread"] = old_multithread
+      response
+    end
+  end
+end

actionpack/lib/action_controller/middleware_stack.rb

@@ -10,10 +10,26 @@ module ActionController
           @klass = klass.to_s.constantize
         end
 
+        options = args.extract_options!
+        if options.has_key?(:if)
+          @conditional = options.delete(:if)
+        else
+          @conditional = true
+        end
+        args << options unless options.empty?
+
         @args = args
         @block = block
       end
 
+      def active?
+        if @conditional.respond_to?(:call)
+          @conditional.call
+        else
+          @conditional
+        end
+      end
+
       def ==(middleware)
         case middleware
         when Middleware
@@ -50,8 +66,12 @@ module ActionController
       push(middleware)
     end
 
+    def active
+      find_all { |middleware| middleware.active? }
+    end
+
     def build(app)
-      reverse.inject(app) { |a, e| e.build(a) }
+      active.reverse.inject(app) { |a, e| e.build(a) }
     end
   end
 end

actionpack/test/controller/dispatcher_test.rb

@@ -50,7 +50,7 @@ class DispatcherTest < Test::Unit::TestCase
   end
 
   def test_failsafe_response
-    Dispatcher.any_instance.expects(:dispatch_unlocked).raises('b00m')
+    Dispatcher.any_instance.expects(:dispatch).raises('b00m')
     ActionController::Failsafe.any_instance.expects(:log_failsafe_exception)
 
     assert_nothing_raised do

railties/lib/tasks/middleware.rake

@@ -1,6 +1,6 @@
 desc 'Prints out your Rack middleware stack'
 task :middleware => :environment do
-  ActionController::Dispatcher.middleware.each do |middleware|
+  ActionController::Dispatcher.middleware.active.each do |middleware|
     puts "use #{middleware.inspect}"
   end
   puts "run ActionController::Dispatcher.new"