// all the tasks, then the thread will block waiting for all
            // those subtasks to finish.
            // This ensures the number of running workers is no more than
            // the defined parallism, while making sure the pool will not
            // be exhausted
            //
            return new ThreadPoolExecutor(
                    parallelism, Integer.MAX_VALUE, 0L, TimeUnit.MILLISECONDS, new LinkedBlockingQueue<>()) {