@Experimental(feature = ExperimentalFeature.PATCH_UPGRADES,
      comment = "can only take the first stack we find until we can support multiple with Kerberos")
  private StackId getStackId(Cluster cluster) throws AmbariException {
    return cluster.getServices().values().iterator().next().getDesiredStackId();
  }
@param serviceName
@param widgetMap
@param sectionLayoutMap
@throws AmbariException
ambari-server/src/main/java/org/apache/ambari/server/upgrade/AbstractUpgradeCatalog.java