@Override
  public String getHostName(String clusterName, String componentName) throws SystemException {
    checkInit();
    return clusterHostComponentMap.get(clusterName).get(componentName);
  }
Get type of Metrics system installed.
@return @MetricsService, null if none found.
ambari-server/src/main/java/org/apache/ambari/server/controller/internal/AbstractProviderModule.java