Add #perform_disconnection to have a place for both callbacks and logging

And using an unlikely-to-clash name.

lib/action_cable/channel/base.rb

@@ -56,11 +56,9 @@ def run_subscribe_callbacks
           send(callback)
         end
       end
-
-      def run_unsubscribe_callbacks
-        self.class.on_unsubscribe_callbacks.each do |callback|
-          send(callback)
-        end
+      def perform_disconnection
+        run_unsubscribe_callbacks
+        logger.info "#{self.class.name} disconnected"
       end
 
       protected
@@ -89,6 +87,11 @@ def broadcast(data)
           end
         end
 
+      private
+        def run_unsubscribe_callbacks
+          self.class.on_unsubscribe_callbacks.each { |callback| send(callback) }
+        end
+
         def start_periodic_timers
           self.class.periodic_timers.each do |callback, options|
             @_active_periodic_timers << EventMachine::PeriodicTimer.new(options[:every]) do

lib/action_cable/connection/base.rb

@@ -81,7 +81,7 @@ def received_data(data)
 
       def cleanup_subscriptions
         @subscriptions.each do |id, channel|
-          channel.run_unsubscribe_callbacks
+          channel.perform_disconnection
         end
       end
 
@@ -161,7 +161,7 @@ def process_message(message)
 
         def unsubscribe_channel(data)
           logger.info "Unsubscribing from channel: #{data['identifier']}"
-          @subscriptions[data['identifier']].run_unsubscribe_callbacks
+          @subscriptions[data['identifier']].perform_disconnection
           @subscriptions.delete(data['identifier'])
         end