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

2 files changed, 131 insertions, 0 deletions

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