Instrument cache store events only if required.

actionpack/test/controller/caching_test.rb

@@ -628,7 +628,7 @@ class FragmentCachingTest < ActionController::TestCase
 
   def test_fragment_for_logging
     fragment_computed = false
-    ActiveSupport::Orchestra.queue.expects(:publish).times(4)
+    ActiveSupport::Orchestra.queue.expects(:publish).times(2)
 
     buffer = 'generated till now -> '
     @controller.fragment_for(buffer, 'expensive') { fragment_computed = true }

activesupport/lib/active_support/cache.rb

@@ -105,7 +105,7 @@ module ActiveSupport
     #   cache.write("city", "Duckburgh")
     #   cache.read("city")   # => "Duckburgh"
     class Store
-      cattr_accessor :logger
+      cattr_accessor :logger, :instance_writter => false
 
       attr_reader :silence
       alias :silence? :silence
@@ -122,6 +122,15 @@ module ActiveSupport
         @silence = previous_silence
       end
 
+      # Set to true if cache stores should be instrumented. By default is false.
+      def self.instrument=(boolean)
+        Thread.current[:instrument_cache_store] = boolean
+      end
+
+      def self.instrument
+        Thread.current[:instrument_cache_store] || false
+      end
+
       # Fetches data from the cache, using the given key. If there is data in
       # the cache with the given key, then that data is returned.
       #
@@ -242,12 +251,15 @@ module ActiveSupport
         end
 
         def instrument(operation, key, options, &block)
+          log(operation, key, options)
+
+          if self.class.instrument
             payload = { :key => key }
             payload.merge!(options) if options.is_a?(Hash)
-
-          # Cache events should be logged or not?
-          # log(operation, key, options)
             ActiveSupport::Orchestra.instrument(:"cache_#{operation}", payload, &block)
+          else
+            yield
+          end
         end
 
         def log(operation, key, options)