private Collection<String> getTopologyRequiredHostGroups() {
    try {
      return configRequest.getRequiredHostGroups();
    } catch (RuntimeException e) {
      // just log error and allow config topology update
      LOG.error("Could not determine required host groups", e);
      return Collections.emptyList();
    }
  }
Return the set of host group names which are required for configuration topology resolution.
ambari-server/src/main/java/org/apache/ambari/server/topology/tasks/ConfigureClusterTask.java