@Subscribe
  public void handleClusterEnvConfigChangedEvent(ClusterConfigChangedEvent event) {
    if (!StringUtils.equals(event.getConfigType(), ConfigHelper.CLUSTER_ENV)) {
      return;
    }

    m_clusterPropertyCache.clear();
  }
Handles {@link ClusterConfigChangedEvent} which means that the
{{cluster-env}} may have changed.

@param event
         the change event.
ambari-server/src/main/java/org/apache/ambari/server/state/cluster/ClusterImpl.java