@Override
  public synchronized RequestStatusResponse updateStacks() throws AmbariException {

    try {
      ambariMetaInfo.init();
    } catch (AmbariException e) {
      throw e;
    } catch (Exception e) {
      throw new AmbariException(
          "Ambari Meta Information can't be read from the stack root directory");
    }

    return null;
  }
Chooses a healthy host from the list of candidate hosts randomly. If there
are no healthy hosts, then this method will return {@code null}.
<p/>
The host's {@link HostState} is used to determine if a host is healthy.

@return a random healthy host, or {@code null}.
@throws AmbariException
@see {@link HostState#HEALTHY}
ambari-server/src/main/java/org/apache/ambari/server/controller/AmbariManagementControllerImpl.java