Notifications: extract central Notifier, cordon off the internal Fanout implementation, and segregate instrumentation concerns

3 files changed, 147 insertions, 132 deletions

diff --git a/activesupport/lib/active_support/notifications.rb b/activesupport/lib/active_support/notifications.rb
index 316d80e064..d9bfcbfcab 100644
--- a/activesupport/lib/active_support/notifications.rb
+++ b/activesupport/lib/active_support/notifications.rb
@@ -1,7 +1,4 @@
-require 'thread'
 require 'active_support/core_ext/module/delegation'
-require 'active_support/core_ext/module/attribute_accessors'
-require 'active_support/secure_random'
 
 module ActiveSupport
   # Notifications provides an instrumentation API for Ruby. To instrument an
@@ -41,155 +38,42 @@ module ActiveSupport
   # to subscribers in a thread. You can use any queue implementation you want.
   #
   module Notifications
-    mattr_accessor :queue
+    autoload :Instrumenter, 'active_support/notifications/instrumenter'
+    autoload :Event, 'active_support/notifications/instrumenter'
+    autoload :Fanout, 'active_support/notifications/fanout'
 
     class << self
-      delegate :instrument, :transaction_id, :transaction, :to => :instrumenter
+      attr_writer :notifier
+      delegate :publish, :subscribe, :instrument, :to => :notifier
 
-      def instrumenter
-        Thread.current[:notifications_instrumeter] ||= Instrumenter.new(publisher)
-      end
-
-      def publisher
-        @publisher ||= Publisher.new(queue)
-      end
-
-      def subscribe(pattern=nil, &block)
-        Subscriber.new(queue).bind(pattern).subscribe(&block)
+      def notifier
+        @notifier ||= Notifier.new
       end
     end
 
-    class Instrumenter
-      def initialize(publisher)
-        @publisher = publisher
-        @id        = random_id
-      end
-
-      def transaction
-        @id, old_id = random_id, @id
-        yield
-      ensure
-        @id = old_id
-      end
-
-      def transaction_id
-        @id
-      end
-
-      def instrument(name, payload={})
-        time   = Time.now
-        result = yield if block_given?
-      ensure
-        @publisher.publish(name, time, Time.now, result, @id, payload)
-      end
-
-    private
-      def random_id
-        SecureRandom.hex(10)
-      end
-    end
-
-    class Publisher
-      def initialize(queue)
+    class Notifier
+      def initialize(queue = Fanout.new)
         @queue = queue
       end
 
       def publish(*args)
         @queue.publish(*args)
       end
-    end
-
-    class Subscriber
-      def initialize(queue)
-        @queue = queue
-      end
 
-      def bind(pattern)
-        @pattern = pattern
-        self
-      end
-
-      def subscribe
-        @queue.subscribe(@pattern) do |*args|
-          yield(*args)
-        end
-      end
-    end
-
-    class Event
-      attr_reader :name, :time, :end, :transaction_id, :result, :payload
-
-      def initialize(name, start, ending, result, transaction_id, payload)
-        @name           = name
-        @payload        = payload.dup
-        @time           = start
-        @transaction_id = transaction_id
-        @end            = ending
-        @result         = result
-      end
-
-      def duration
-        @duration ||= 1000.0 * (@end - @time)
-      end
-
-      def parent_of?(event)
-        start = (self.time - event.time) * 1000
-        start <= 0 && (start + duration >= event.duration)
-      end
-    end
-
-    # This is a default queue implementation that ships with Notifications. It
-    # consumes events in a thread and publish them to all registered subscribers.
-    #
-    class LittleFanout
-      def initialize
-        @listeners = []
-      end
-
-      def publish(*args)
-        @listeners.each { |l| l.publish(*args) }
-      end
-
-      def subscribe(pattern=nil, &block)
-        @listeners << Listener.new(pattern, &block)
+      def subscribe(pattern = nil, &block)
+        @queue.bind(pattern).subscribe(&block)
       end
 
       def wait
-        sleep 0.05 until drained?
+        @queue.wait
       end
 
-      private
-        def drained?
-          @listeners.all? &:drained?
-        end
-
-      # Used for internal implementation only.
-      class Listener #:nodoc:
-        def initialize(pattern, &block)
-          @pattern = pattern
-          @subscriber = block
-          @queue = Queue.new
-          Thread.new { consume }
-        end
-
-        def publish(name, *args)
-          if !@pattern || @pattern === name.to_s
-            @queue << args.unshift(name)
-          end
-        end
-
-        def consume
-          while args = @queue.shift
-            @subscriber.call(*args)
-          end
-        end
+      delegate :instrument, :to => :current_instrumenter
 
-        def drained?
-          @queue.size.zero?
+      private
+        def current_instrumenter
+          Thread.current[:"instrumentation_#{object_id}"] ||= Notifications::Instrumenter.new(self)
         end
-      end
     end
   end
-
-  Notifications.queue = Notifications::LittleFanout.new
 end
diff --git a/activesupport/lib/active_support/notifications/fanout.rb b/activesupport/lib/active_support/notifications/fanout.rb
new file mode 100644
index 0000000000..412d977b25
--- /dev/null
+++ b/activesupport/lib/active_support/notifications/fanout.rb
@@ -0,0 +1,84 @@
+require 'thread'
+
+module ActiveSupport
+  module Notifications
+    # This is a default queue implementation that ships with Notifications. It
+    # consumes events in a thread and publish them to all registered subscribers.
+    #
+    class Fanout
+      def initialize
+        @subscribers = []
+      end
+
+      def bind(pattern)
+        Binding.new(self, pattern)
+      end
+
+      def subscribe(pattern = nil, &block)
+        @subscribers << Subscriber.new(pattern, &block)
+      end
+
+      def publish(*args)
+        @subscribers.each { |s| s.publish(*args) }
+      end
+
+      def wait
+        sleep(0.05) until @subscribers.all?(&:drained?)
+      end
+
+      # Used for internal implementation only.
+      class Binding #:nodoc:
+        def initialize(queue, pattern)
+          @queue, @pattern = queue, pattern
+        end
+
+        def subscribe(&block)
+          @queue.subscribe(@pattern, &block)
+        end
+      end
+
+      # Used for internal implementation only.
+      class Subscriber #:nodoc:
+        def initialize(pattern, &block)
+          @pattern =
+            case pattern
+            when Regexp, NilClass
+              pattern
+            else
+              /^#{Regexp.escape(pattern.to_s)}/
+            end
+          @block = block
+          @events = Queue.new
+          start_consumer
+        end
+
+        def publish(name, *args)
+          push(name, args) if matches?(name)
+        end
+
+        def consume
+          while args = @events.shift
+            @block.call(*args)
+          end
+        end
+
+        def drained?
+          @events.size.zero?
+        end
+
+        private
+          def start_consumer
+            Thread.new { consume }
+          end
+
+          def matches?(name)
+            !@pattern || @pattern =~ name.to_s
+          end
+
+          def push(name, args)
+            @events << args.unshift(name)
+          end
+      end
+    end
+  end
+end
diff --git a/activesupport/lib/active_support/notifications/instrumenter.rb b/activesupport/lib/active_support/notifications/instrumenter.rb
new file mode 100644
index 0000000000..fb95422af2
--- /dev/null
+++ b/activesupport/lib/active_support/notifications/instrumenter.rb
@@ -0,0 +1,47 @@
+require 'active_support/secure_random'
+require 'active_support/core_ext/module/delegation'
+
+module ActiveSupport
+  module Notifications
+    class Instrumenter
+      def initialize(notifier)
+        @id = unique_id
+        @notifier = notifier
+      end
+
+      def instrument(name, payload={})
+        time   = Time.now
+        result = yield if block_given?
+      ensure
+        @notifier.publish(name, time, Time.now, result, @id, payload)
+      end
+
+      private
+        def unique_id
+          SecureRandom.hex(10)
+        end
+    end
+
+    class Event
+      attr_reader :name, :time, :end, :transaction_id, :result, :payload
+
+      def initialize(name, start, ending, result, transaction_id, payload)
+        @name           = name
+        @payload        = payload.dup
+        @time           = start
+        @transaction_id = transaction_id
+        @end            = ending
+        @result         = result
+      end
+
+      def duration
+        @duration ||= 1000.0 * (@end - @time)
+      end
+
+      def parent_of?(event)
+        start = (self.time - event.time) * 1000
+        start <= 0 && (start + duration >= event.duration)
+      end
+    end
+  end
+end