private <T> RequestDelegate<T> createRequestDelegate() {
    return new ParallelRequestDelegate<>(endpoints, queryTimeoutSeconds);
  }
As each query operation in one ResultSet may send another RPCs to server, the request should be
executed in parallel in order to accelerate the test.
integration-test/src/main/java/org/apache/iotdb/itbase/runtime/ClusterTestResultSet.java