@Subscribe
  @AllowConcurrentEvents
  public void onAmbariEvent(ClusterEvent event) {
    LOG.debug("Received event {}", event);

    if( event.getType() != AmbariEventType.CLUSTER_RENAME ) {
      return;
    }


    AlertDefinitionHash hash = m_alertDefinitionHash.get();
    hash.invalidateAll();

    long clusterId = event.getClusterId();
    hash.enqueueAgentCommands(clusterId);
  }
Handles {@link ClusterEvent} by performing the following tasks:
<ul>
<li>Invalidates all alerts across all hosts. This is because agents use the
cluster name as an identifier and if the cluster is renamed, then they need
to be rescheduled.</li>
</ul>

@param event
         the event being handled.
ambari-server/src/main/java/org/apache/ambari/server/events/listeners/alerts/AlertHashInvalidationListener.java