synchronized List<Pair<ServerName, Long>> copyDeadServersSince(long ts) {
    List<Pair<ServerName, Long>> res = new ArrayList<>(size());

    for (Map.Entry<ServerName, Long> entry : deadServers.entrySet()) {
      if (entry.getValue() >= ts) {
        res.add(new Pair<>(entry.getKey(), entry.getValue()));
      }
    }

    Collections.sort(res, (o1, o2) -> o1.getSecond().compareTo(o2.getSecond()));
    return res;
  }
Extract all the servers dead since a given time, and sort them.
@param ts the time, 0 for all
@return a sorted array list, by death time, lowest values first.
hbase-server/src/main/java/org/apache/hadoop/hbase/master/DeadServer.java