@Override
  public List<ServiceComponentHost> getServiceComponentHosts(String serviceName, String componentName) {
    ArrayList<ServiceComponentHost> foundItems = new ArrayList<>();

    ConcurrentMap<String, ConcurrentMap<String, ServiceComponentHost>> foundByService = serviceComponentHosts.get(
        serviceName);
    if (foundByService != null) {
      if (componentName == null) {
        for (Map<String, ServiceComponentHost> foundByComponent : foundByService.values()) {
          foundItems.addAll(foundByComponent.values());
        }
      } else if (foundByService.containsKey(componentName)) {
        foundItems.addAll(foundByService.get(componentName).values());
      }
    }

    return foundItems;
  }
Make sure we load all the service host components.
We need this for live status checks.
ambari-server/src/main/java/org/apache/ambari/server/state/cluster/ClusterImpl.java