TPL数据流管道完成未从等待中返回

Question

我有一个管道，即使所有数据都已处理并显示在控制台上，也无法注册为完整管道。我将其设置为等待完成，但是它永远不会完成，并且不允许方法返回。

    TransformBlock<string, CompanyInfo> GetCompanyInfo;
    TransformBlock<string, List<Dividend>> GetDividendReports;
    TransformBlock<string, KeyStats> GetKeyStatInfo;
    TransformBlock<string, List<Interval>> GetIntervalReports;
    TransformBlock<List<Interval>, List<decimal>> GetChangesOverInterval;
    BroadcastBlock<string> broadcastSymbol;
    TransformBlock<Tuple<List<decimal>, List<Dividend>, KeyStats>, string> GenerateXmlString;
    ActionBlock<string> GenerateCompleteReport;
    CancellationTokenSource cancellationTokenSource;


    public Task StartPipeline()
    {
        cancellationTokenSource = new CancellationTokenSource();

        ExecutionDataflowBlockOptions executionDataflowBlockOptions = new ExecutionDataflowBlockOptions
        {
            CancellationToken = cancellationTokenSource.Token,
            MaxDegreeOfParallelism = MAXPARA
        };

        broadcastSymbol = new BroadcastBlock<string>(symbol => symbol);
        var joinblock = new JoinBlock<List<decimal>, List<Dividend>, KeyStats>(new GroupingDataflowBlockOptions { Greedy = false });

        GetCompanyInfo = new TransformBlock<string, CompanyInfo>(symbol =>
        {
            return RetrieveCompanyInfo(symbol);
        }, executionDataflowBlockOptions);

        GetDividendReports = new TransformBlock<string, List<Dividend>>(symbol =>
        {
            return RetrieveDividendInfo(symbol);
        }, executionDataflowBlockOptions);

        GetKeyStatInfo = new TransformBlock<string, KeyStats>(symbol =>
        {
            return RetrieveKeyStats(symbol);
        }, executionDataflowBlockOptions);

        GetIntervalReports = new TransformBlock<string, List<Interval>>(symbol =>
        {
            return RetrieveIntervals(symbol, 30);
        }, executionDataflowBlockOptions);

        GetChangesOverInterval = new TransformBlock<List<Interval>, List<decimal>>(intervals =>
        {
            return ConstructIntervalReport(intervals);
        }, executionDataflowBlockOptions);

        GenerateXmlString = new TransformBlock<Tuple<List<decimal>, List<Dividend>, KeyStats>, string>(tup =>
        {
            var ReportObj = new Report
            {
                changeIntervals = tup.Item1,
                dividends = tup.Item2,
                keyStats = tup.Item3
            };

            XmlSerializer ser = new XmlSerializer(typeof(Report));
            var stringWriter = new StringWriter();
            ser.Serialize(stringWriter, ReportObj);
            return stringWriter.ToString();

        }, executionDataflowBlockOptions);

        GenerateCompleteReport = new ActionBlock<string>(xml =>
        {
            var str = Path.GetRandomFileName().Replace(".", "") + ".xml";
            File.WriteAllText(str, xml);
            Console.WriteLine("Finished File");
        }, executionDataflowBlockOptions);

        var options = new DataflowLinkOptions { PropagateCompletion = true };

        var buffer = new BufferBlock<string>();
        buffer.LinkTo(broadcastSymbol);

        //Broadcasts the symbol
        broadcastSymbol.LinkTo(GetIntervalReports, options);
        broadcastSymbol.LinkTo(GetDividendReports, options);
        broadcastSymbol.LinkTo(GetKeyStatInfo, options);
        //Second teir parallel 
        GetIntervalReports.LinkTo(GetChangesOverInterval, options);
        //Joins the parallel blocks back together
        GetDividendReports.LinkTo(joinblock.Target2, options);
        GetKeyStatInfo.LinkTo(joinblock.Target3, options);
        GetChangesOverInterval.LinkTo(joinblock.Target1, options);

        joinblock.LinkTo(GenerateXmlString, options);
        GenerateXmlString.LinkTo(GenerateCompleteReport, options);

        buffer.Post("F");
        buffer.Post("AGFS");
        buffer.Post("BAC");
        buffer.Post("FCF");

        buffer.Complete();

        GenerateCompleteReport.Completion.Wait(cancellationTokenSource.Token);

    }

我不确定为什么没有从管道返回异常或完成。程序运行时，它会显示所有正在创建和停止的文件，但是等待完成后没有代码执行。 PropagateCompletion是否不应该让这些块知道它们何时完成其动作或转换？

Answer 1

您没有将链接选项传递给BufferBlock，因此不会传播完成。另一方面，只有一个链接的块将从您的BroadcastBlock处接收完成。如果要等待所有三个链接的块，则必须自己显式处理。 See here for an example

另外，由于该方法已经返回了Task，而不必返回Task.CompletedTask，因此您可以简单地使用async/sawait而不用.Wait()进行阻塞。您希望await将此方法与null一起使用的调用方有什么用？

if (GenerateCompleteReport.Completion.IsCompletedSuccessfully) { return Task.CompletedTask;  }

        return null;

相反，您可以：

await enerateCompleteReport.Completion

Answer 2

问题最终没有将传播链接到缓冲区块，缓冲区块不允许任何块接收完成事件。另外，我需要让广播中的所有接收块都接收完整的状态，因为我不知道广播块仅向链接的块之一发送完整的事件。

添加这些更改后，管道将按我预期的那样工作。

    readonly string _baseUrl = "https://api.iextrading.com/1.0/";
    const int MAXPARA = 2;

    TransformBlock<string, CompanyInfo> GetCompanyInfo;
    TransformBlock<string, List<Dividend>> GetDividendReports;
    TransformBlock<string, KeyStats> GetKeyStatInfo;
    TransformBlock<string, List<Interval>> GetIntervalReports;
    TransformBlock<List<Interval>, List<decimal>> GetChangesOverInterval;
    BroadcastBlock<string> broadcastSymbol;
    TransformBlock<Tuple<List<decimal>, List<Dividend>, KeyStats>, string> GenerateXmlString;
    ActionBlock<string> GenerateCompleteReport;
    CancellationTokenSource cancellationTokenSource;

    public void StartPipeline()
    {

        //Add cancelation to the pipeline
        cancellationTokenSource = new CancellationTokenSource();

        ExecutionDataflowBlockOptions executionDataflowBlockOptions = new ExecutionDataflowBlockOptions
        {
            CancellationToken = cancellationTokenSource.Token,
            MaxDegreeOfParallelism = MAXPARA
        };

        broadcastSymbol = new BroadcastBlock<string>(symbol => symbol);
        var joinblock = new JoinBlock<List<decimal>, List<Dividend>, KeyStats>(new GroupingDataflowBlockOptions { Greedy = false });

        GetCompanyInfo = new TransformBlock<string, CompanyInfo>(symbol =>
        {
            return RetrieveCompanyInfo(symbol);
        }, executionDataflowBlockOptions);

        GetDividendReports = new TransformBlock<string, List<Dividend>>(symbol =>
        {
            return RetrieveDividendInfo(symbol);
        }, executionDataflowBlockOptions);

        GetKeyStatInfo = new TransformBlock<string, KeyStats>(symbol =>
        {
            return RetrieveKeyStats(symbol);
        }, executionDataflowBlockOptions);

        GetIntervalReports = new TransformBlock<string, List<Interval>>(symbol =>
        {
            return RetrieveIntervals(symbol, 30);
        }, executionDataflowBlockOptions);

        GetChangesOverInterval = new TransformBlock<List<Interval>, List<decimal>>(intervals =>
        {
            return ConstructIntervalReport(intervals);
        }, executionDataflowBlockOptions);

        GenerateXmlString = new TransformBlock<Tuple<List<decimal>, List<Dividend>, KeyStats>, string>(tup =>
        {
            var ReportObj = new Report
            {
                changeIntervals = tup.Item1,
                dividends = tup.Item2,
                keyStats = tup.Item3
            };

            XmlSerializer ser = new XmlSerializer(typeof(Report));
            var stringWriter = new StringWriter();
            ser.Serialize(stringWriter, ReportObj);
            return stringWriter.ToString();

        }, executionDataflowBlockOptions);

        GenerateCompleteReport = new ActionBlock<string>(xml =>
        {
            var str = Path.GetRandomFileName().Replace(".", "") + ".xml";
            File.WriteAllText(str, xml);
            Console.WriteLine("Finished File");
        }, executionDataflowBlockOptions);

        var options = new DataflowLinkOptions { PropagateCompletion = true };

        var buffer = new BufferBlock<string>();
        buffer.LinkTo(broadcastSymbol, options);

        //Need to make sure all data is recieved for each linked block
        //Broadcast block only sends completion notice to one of the linked blocks
        broadcastSymbol.Completion.ContinueWith(tsk =>
        {
            if(!tsk.IsFaulted)
            {
                GetIntervalReports.Complete();
                GetDividendReports.Complete();
                GetKeyStatInfo.Complete();
            }
            else
            {
                ((IDataflowBlock)GetIntervalReports).Fault(tsk.Exception);
                ((IDataflowBlock)GetDividendReports).Fault(tsk.Exception);
                ((IDataflowBlock)GetKeyStatInfo).Fault(tsk.Exception);
            }
        });


        //Broadcasts the symbol
        broadcastSymbol.LinkTo(GetIntervalReports, options);
        broadcastSymbol.LinkTo(GetDividendReports, options);
        broadcastSymbol.LinkTo(GetKeyStatInfo, options);
        //Second teir parallel 
        GetIntervalReports.LinkTo(GetChangesOverInterval, options);
        //Joins the parallel blocks back together
        GetDividendReports.LinkTo(joinblock.Target2, options);
        GetKeyStatInfo.LinkTo(joinblock.Target3, options);
        GetChangesOverInterval.LinkTo(joinblock.Target1, options);

        joinblock.LinkTo(GenerateXmlString, options);
        GenerateXmlString.LinkTo(GenerateCompleteReport, options);

        buffer.Post("F");
        buffer.Post("AGFS");
        buffer.Post("BAC");
        buffer.Post("FCF");


        buffer.Complete();

        GenerateCompleteReport.Completion.Wait(cancellationTokenSource.Token);

    }