@Override
  public List<T> requestAll() throws SQLException {
    List<T> results = new ArrayList<>(getEndpoints().size());
    Exception[] exceptions = new Exception[getEndpoints().size()];
    for (int i = 0; i < getEndpoints().size(); i++) {
      try {
        results.add(getRequests().get(i).call());
      } catch (Exception e) {
        exceptions[i] = e;
      }
    }
    handleExceptions(exceptions);
    return results;
  }
ParallelRequestDelegate will handle requests in serial. It's more efficient when the requests are
just local computation.
integration-test/src/main/java/org/apache/iotdb/itbase/runtime/SerialRequestDelegate.java