From b0a16a97762c4cdcf36403d46968930099ddcd0f Mon Sep 17 00:00:00 2001
From: Aaron Patterson <aaron.patterson@gmail.com>
Date: Thu, 26 Jul 2018 12:03:31 -0700
Subject: Subscribe to event objects via `subscribe_event`

Fanout notifier can send event objects to subscribers now.  Also moved
`end` lower in the `finish!` method to guarantee that CPU time is
shorter than real time.
---
 .../lib/active_support/notifications/fanout.rb     | 38 ++++++++++++++++++++++
 .../active_support/notifications/instrumenter.rb   |  2 +-
 2 files changed, 39 insertions(+), 1 deletion(-)

(limited to 'activesupport/lib/active_support/notifications')

diff --git a/activesupport/lib/active_support/notifications/fanout.rb b/activesupport/lib/active_support/notifications/fanout.rb
index 25aab175b4..91d8491c7e 100644
--- a/activesupport/lib/active_support/notifications/fanout.rb
+++ b/activesupport/lib/active_support/notifications/fanout.rb
@@ -27,6 +27,15 @@ module ActiveSupport
         subscriber
       end
 
+      def subscribe_event(pattern = nil, &block)
+        subscriber = Subscribers.event_object_subscriber pattern, block
+        synchronize do
+          @subscribers << subscriber
+          @listeners_for.clear
+        end
+        subscriber
+      end
+
       def unsubscribe(subscriber_or_name)
         synchronize do
           case subscriber_or_name
@@ -76,6 +85,14 @@ module ActiveSupport
             subscriber = Timed.new pattern, listener
           end
 
+          wrap_all pattern, subscriber
+        end
+
+        def self.event_object_subscriber(pattern, block)
+          wrap_all pattern, EventObject.new(pattern, block)
+        end
+
+        def self.wrap_all(pattern, subscriber)
           unless pattern
             AllMessages.new(subscriber)
           else
@@ -130,6 +147,27 @@ module ActiveSupport
           end
         end
 
+        class EventObject < Evented
+          def start(name, id, payload)
+            stack = Thread.current[:_event_stack] ||= []
+            event = build_event name, id, payload
+            event.start!
+            stack.push event
+          end
+
+          def finish(name, id, payload)
+            stack = Thread.current[:_event_stack]
+            event = stack.pop
+            event.finish!
+            @delegate.call event
+          end
+
+          private
+            def build_event(name, id, payload)
+              ActiveSupport::Notifications::Event.new name, nil, nil, id, payload
+            end
+        end
+
         class AllMessages # :nodoc:
           def initialize(delegate)
             @delegate = delegate
diff --git a/activesupport/lib/active_support/notifications/instrumenter.rb b/activesupport/lib/active_support/notifications/instrumenter.rb
index 259cb4db98..72e5064679 100644
--- a/activesupport/lib/active_support/notifications/instrumenter.rb
+++ b/activesupport/lib/active_support/notifications/instrumenter.rb
@@ -76,8 +76,8 @@ module ActiveSupport
       end
 
       def finish!
-        @end = now
         @cpu_time_finish = now_cpu
+        @end = now
         @allocation_count_finish = now_allocations
       end
 
-- 
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