private RetriesExhaustedWithDetailsException makeError() {
    List<Row> rows = new ArrayList<>();
    List<Throwable> throwables = new ArrayList<>();
    List<String> hostnameAndPorts = new ArrayList<>();
    for (;;) {
      Pair<Mutation, Throwable> pair = errors.poll();
      if (pair == null) {
        break;
      }
      rows.add(pair.getFirst());
      throwables.add(pair.getSecond());
      hostnameAndPorts.add(getHostnameAndPort(pair.getSecond()));
    }
    return new RetriesExhaustedWithDetailsException(throwables, rows, hostnameAndPorts);
  }
{@link BufferedMutator} implementation based on {@link AsyncBufferedMutator}.
hbase-client/src/main/java/org/apache/hadoop/hbase/client/BufferedMutatorOverAsyncBufferedMutator.java