5 files changed, 130 insertions, 0 deletions
diff --git a/actionpack/lib/action_controller.rb b/actionpack/lib/action_controller.rb
index 7c10fcbb8a..1d06c83338 100644
--- a/actionpack/lib/action_controller.rb
+++ b/actionpack/lib/action_controller.rb
@@ -1,5 +1,6 @@
 require 'abstract_controller'
 require 'action_dispatch'
+require 'action_controller/metal/live'
 
 module ActionController
   extend ActiveSupport::Autoload
diff --git a/actionpack/lib/action_controller/metal/live.rb b/actionpack/lib/action_controller/metal/live.rb
new file mode 100644
index 0000000000..aea00849d3
--- /dev/null
+++ b/actionpack/lib/action_controller/metal/live.rb
@@ -0,0 +1,42 @@
+require 'action_dispatch/http/response'
+
+module ActionController
+  module Live
+    class Response < ActionDispatch::Response
+      class Buffer < ActionDispatch::Response::Buffer # :nodoc:
+        def initialize(response)
+          @response = response
+          @buf      = Queue.new
+        end
+
+        def write(string)
+          unless @response.committed?
+            @response.headers["Cache-Control"] = "no-cache"
+            @response.headers.delete("Content-Length")
+          end
+
+          super
+        end
+
+        def each
+          while str = @buf.pop
+            yield str
+          end
+        end
+
+        def close
+          super
+          @buf.push nil
+        end
+      end
+
+      private
+
+      def build_buffer(response, body)
+        buf = Buffer.new response
+        body.each { |part| buf.write part }
+        buf
+      end
+    end
+  end
+end
diff --git a/actionpack/test/controller/live_stream_test.rb b/actionpack/test/controller/live_stream_test.rb
new file mode 100644
index 0000000000..6ee6444065
--- /dev/null
+++ b/actionpack/test/controller/live_stream_test.rb
@@ -0,0 +1,26 @@
+require 'abstract_unit'
+
+module ActionController
+  class StreamingResponseTest < ActionController::TestCase
+    class TestController < ActionController::Base
+      def self.controller_path
+        'test'
+      end
+
+      def basic_stream
+        %w{ hello world }.each do |word|
+          response.stream.write word
+          response.stream.write "\n"
+        end
+        response.stream.close
+      end
+    end
+
+    tests TestController
+
+    def test_write_to_stream
+      get :basic_stream
+      assert_equal "hello\nworld\n", @response.body
+    end
+  end
+end
diff --git a/actionpack/test/dispatch/live_response_test.rb b/actionpack/test/dispatch/live_response_test.rb
new file mode 100644
index 0000000000..0e8dcc6a16
--- /dev/null
+++ b/actionpack/test/dispatch/live_response_test.rb
@@ -0,0 +1,34 @@
+require 'abstract_unit'
+require 'active_support/concurrency/latch'
+
+module ActionController
+  module Live
+    class ResponseTest < ActiveSupport::TestCase
+      def setup
+        @response = Live::Response.new
+      end
+
+      def test_parallel
+        latch = ActiveSupport::Concurrency::Latch.new
+
+        t = Thread.new {
+          @response.stream.write 'foo'
+          latch.await
+          @response.stream.close
+        }
+
+        @response.each do |part|
+          assert_equal 'foo', part
+          latch.release
+        end
+        assert t.join
+      end
+
+      def test_setting_body_populates_buffer
+        @response.body = 'omg'
+        @response.close
+        assert_equal ['omg'], @response.body_parts
+      end
+    end
+  end
+end
diff --git a/activesupport/lib/active_support/concurrency/latch.rb b/activesupport/lib/active_support/concurrency/latch.rb
new file mode 100644
index 0000000000..1507de433e
--- /dev/null
+++ b/activesupport/lib/active_support/concurrency/latch.rb
@@ -0,0 +1,27 @@
+require 'thread'
+require 'monitor'
+
+module ActiveSupport
+  module Concurrency
+    class Latch
+      def initialize(count = 1)
+        @count = count
+        @lock = Monitor.new
+        @cv = @lock.new_cond
+      end
+
+      def release
+        @lock.synchronize do
+          @count -= 1 if @count > 0
+          @cv.broadcast if @count.zero?
+        end
+      end
+
+      def await
+        @lock.synchronize do
+          @cv.wait_while { @count > 0 }
+        end
+      end
+    end
+  end
+end