当我使用 await Console.Out.WriteLineAsync 时，程序永远不会完成

Question

我在 .NET 4.7.1 中使用 DataFlow 库由于某种原因，当我await Console.Out.WriteLineAsync(DateTime.Now.TimeOfDay.ToString());在构造函数的asynclambda 中时，我的程序永远不会终止。ActionBlock它只会输出行的流DateTime.Now.TimeOfDay.ToString()并随机停止，永远不会到达Console.WriteLine("Time elapsed:" + watch.Elapsed);，尽管在某些情况下我观察到控制台输出"Finished Reading the file"。

 class Program

    {

        public static async Task Main(string[] args)

        {

            int numberOfLines = 0;

            Console.WriteLine("Number of cores used:" + Convert.ToInt32(Math.Ceiling((Environment.ProcessorCount * 0.75) * 2.0)));

            BufferBlock<string> queBuffer = new BufferBlock<string>(new DataflowBlockOptions { BoundedCapacity = 100000 });

            var processingBlock = new ActionBlock<string>(async inputline =>

            {

                Interlocked.Increment(ref numberOfLines);

                //Line that causes issue

                //await Console.Out.WriteLineAsync(DateTime.Now.TimeOfDay.ToString());

            }

            , new ExecutionDataflowBlockOptions()

            {

                MaxDegreeOfParallelism = 48,

                SingleProducerConstrained = true,

                BoundedCapacity = 500

            });

            queBuffer.LinkTo(processingBlock);

            //Start

            var watch = System.Diagnostics.Stopwatch.StartNew();

            Console.WriteLine("Processing started at:" + DateTime.Now);

            if (File.Exists(args[0]))

            {

                using (StreamReader sr = new StreamReader(args[0]))

                {

        }

    }

但是，如果我取出导致问题的行，它会工作并从文本文件中读取所有行。 W:\test>.\CompressAMS.exe token2-small.txt

Number of cores used:24

Processing started at:12/17/2018 6:32:50 PM

Finished Reading the file

Time elapsed:00:00:00.3569824

Number of lines read:100000

Answer 1

当你完成时，你所拥有的是一个竞争条件。您正在调用Complete()两个块，强制处理块停止接收消息，此时缓冲区可能仍有数据要传递。然后，当您等待两个块完成时，如果缓冲区尚未发送所有消息，它将永远不会完成并且执行将挂起Finished Reading File。您可以安全地等待两个块，但只调用Complete()缓冲区并允许 TDF 将完成传播到下游处理块：queBuffer.LinkTo(processingBlock, new DataflowLinkOptions() { PropagateCompletion = true });/******/queBuffer.Complete();await Task.WhenAll(queBuffer.Completion, processingBlock.Completion);