@Override
  public List<ServiceComponentHost> getServiceComponentHosts() {
    List<ServiceComponentHost> serviceComponentHosts = new ArrayList<>();
    if (!serviceComponentHostsByHost.isEmpty()) {
      for (List<ServiceComponentHost> schList : serviceComponentHostsByHost.values()) {
        serviceComponentHosts.addAll(schList);
      }
    }
    return Collections.unmodifiableList(serviceComponentHosts);
  }
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