instrumenter should be accessible from ActiveSupport::Notifications.

activesupport/lib/active_support/notifications.rb

@@ -44,11 +44,16 @@ module Notifications
 
     class << self
       attr_writer :notifier
-      delegate :publish, :subscribe, :instrument, :to => :notifier
+      delegate :publish, :subscribe, :to => :notifier
+      delegate :instrument, :to => :instrumenter
 
       def notifier
         @notifier ||= Notifier.new
       end
+
+      def instrumenter
+        Thread.current[:"instrumentation_#{notifier.object_id}"] ||= Instrumenter.new(notifier)
+      end
     end
 
     class Notifier
@@ -67,13 +72,6 @@ def subscribe(pattern = nil, &block)
       def wait
         @queue.wait
       end
-
-      delegate :instrument, :to => :current_instrumenter
-
-      private
-        def current_instrumenter
-          Thread.current[:"instrumentation_#{object_id}"] ||= Notifications::Instrumenter.new(self)
-        end
     end
   end
 end

activesupport/test/notifications_test.rb

@@ -5,7 +5,8 @@ class TestCase < ActiveSupport::TestCase
     def setup
       Thread.abort_on_exception = true
 
-      @notifier = ActiveSupport::Notifications::Notifier.new
+      ActiveSupport::Notifications.notifier = nil
+      @notifier = ActiveSupport::Notifications.notifier
       @events = []
       @notifier.subscribe { |*args| @events << event(*args) }
     end
@@ -82,17 +83,19 @@ def setup
   end
 
   class InstrumentationTest < TestCase
+    delegate :instrument, :to => ActiveSupport::Notifications
+
     def test_instrument_returns_block_result
-      assert_equal 2, @notifier.instrument(:awesome) { 1 + 1 }
+      assert_equal 2, instrument(:awesome) { 1 + 1 }
     end
 
     def test_instrumenter_exposes_its_id
-      assert_equal 20, ActiveSupport::Notifications::Instrumenter.new(@notifier).id.size
+      assert_equal 20, ActiveSupport::Notifications.instrumenter.id.size
     end
 
     def test_nested_events_can_be_instrumented
-      @notifier.instrument(:awesome, :payload => "notifications") do
-        @notifier.instrument(:wot, :payload => "child") do
+      instrument(:awesome, :payload => "notifications") do
+        instrument(:wot, :payload => "child") do
           1 + 1
         end
 
@@ -112,7 +115,7 @@ def test_nested_events_can_be_instrumented
 
     def test_instrument_publishes_when_exception_is_raised
       begin
-        @notifier.instrument(:awesome, :payload => "notifications") do
+        instrument(:awesome, :payload => "notifications") do
           raise "OMG"
         end
         flunk
@@ -127,7 +130,7 @@ def test_instrument_publishes_when_exception_is_raised
     end
 
     def test_event_is_pushed_even_without_block
-      @notifier.instrument(:awesome, :payload => "notifications")
+      instrument(:awesome, :payload => "notifications")
       drain
 
       assert_equal 1, @events.size