question: private boolean sendEventToListeners ( ClusterEvent event ) { boolean success = true ; for ( String listenerId : Collections . unmodifiableSet ( listeners . keySet ( ) ) ) { logger . debug ( "Notifying listener {} of event {} for instance {}" , listenerId , event . getType ( ) , instanceId ) ; ClusterEventListener listener = listeners . get ( listenerId ) ; if ( listener != null && ! listener . handleEvent ( event ) ) { success = false ; } } return success ; }
target:  Sends a ClusterEvent to all registered listeners