@Override
    public void handleNotification(Notification notification, Object handback) {
      NotificationKey key = new NotificationKey(name);
      notification.setUserData(memberSource);
      repo.putEntryInLocalNotificationRegion(key, notification);
    }
Counter to indicate how many listener are attached to this MBean
geode-core/src/main/java/org/apache/geode/management/internal/NotificationHub.java