Merge pull request #15037 from roccoblues/fix_duplicate_activesupport_subscribers

Fixed duplicate subscribers in ActiveSupport::Subscriber

Conflicts:
	activesupport/CHANGELOG.md

1 files changed, 10 insertions, 1 deletions

diff --git a/activesupport/lib/active_support/subscriber.rb b/activesupport/lib/active_support/subscriber.rb
index 4b9b48539f..98be78b41b 100644
--- a/activesupport/lib/active_support/subscriber.rb
+++ b/activesupport/lib/active_support/subscriber.rb
@@ -64,12 +64,21 @@ module ActiveSupport
       def add_event_subscriber(event)
         return if %w{ start finish }.include?(event.to_s)
 
-        notifier.subscribe("#{event}.#{namespace}", subscriber)
+        pattern = "#{event}.#{namespace}"
+
+        # don't add multiple subscribers (eg. if methods are redefined)
+        return if subscriber.patterns.include?(pattern)
+
+        subscriber.patterns << pattern
+        notifier.subscribe(pattern, subscriber)
       end
     end
 
+    attr_reader :patterns # :nodoc:
+
     def initialize
       @queue_key = [self.class.name, object_id].join "-"
+      @patterns  = []
       super
     end