public Set<String> getServicesByAlertState(String alertState) {
      return m_servicesByState.get(alertState);
    }
Gets a list of services that have an alert being reporting for the given
state.

@param alertState
         the state to get the services for.
@return the services or {@code null} if none.
ambari-server/src/main/java/org/apache/ambari/server/state/services/AlertNoticeDispatchService.java