public Map<Long, Long> getStaleAlerts(Long hostId) {
    return staleAlerts.containsKey(hostId) ? new HashMap<>(staleAlerts.get(hostId)) : Collections.emptyMap();
  }
Retrieves stale alerts for specified host.
@param hostId host id
@return
ambari-server/src/main/java/org/apache/ambari/server/state/alert/AlertHelper.java