TPL 数据流：为什么以下阻塞？

Question

为什么调用 Run() 会阻塞而 return 不会？

它正确地打印了以下输出，这是有道理的。因为我已经初始化大小为 170 的 BatchBlock() 并创建了 200 个 volapoint 对象。但为什么不 return?

ConvertToVolaSurface 
ConvertToVolaSurface 
CalculateStrangles
CalculateStrangles

这是我正在使用的代码片段

class Pipeline
{
    public void Run()
    {
        // Grouping block - Collect vola points until vola surface is full 
        var batchBlock1 = new BatchBlock<VolaPoint>(170);

        // Execution block - Convert vola points to surface
        var transformBlock0 = new TransformBlock<VolaPoint[], VolaSurface>(x => this.ConvertToVolaSurface(x));

        // Execution block - Calculate strangles 
        var transformBlock1 = new TransformBlock<VolaSurface, VolaSurface>(x => this.CalculateStrangles(x));

        var linkOptions = new DataflowLinkOptions()
        {
            PropagateCompletion = true
        };

        batchBlock1.LinkTo(transformBlock0, linkOptions);
        transformBlock0.LinkTo(transformBlock1, linkOptions);

        for (int i = 0; i <= 200; i++)
        {
            batchBlock1.Post(new VolaPoint());
        }

        batchBlock1.Complete();

        transformBlock1.Completion.Wait();
    }

    private VolaSurface ConvertToVolaSurface(VolaPoint[] volapoints)
    {
        Debug.WriteLine("ConvertToVolaSurface");

        return new VolaSurface();
    }

    private VolaSurface CalculateStrangles(VolaSurface volaSurface)
    {
        Debug.WriteLine("CalculateStrangles");

        return volaSurface;
    }
}

Answer 1

你的最后一个块是 TransformBlock，转换块有一个输出缓冲区，它必须是空的才能 Complete。将最后一个块更改为 ActionBlock 并且 await 它已完成，不会阻塞调用线程。

public async Task Run()
{
    // Grouping block - Collect vola points until vola surface is full 
    var batchBlock1 = new BatchBlock<VolaPoint>(170);

    // Execution block - Convert vola points to surface
    var transformBlock0 = new TransformBlock<VolaPoint[], VolaSurface>(x => this.ConvertToVolaSurface(x));

    // Execution block - Calculate strangles 
    var actionBlock1 = new ActionBlock<VolaSurface>(x => this.CalculateStrangles(x));

    var linkOptions = new DataflowLinkOptions()
    {
        PropagateCompletion = true
    };

    batchBlock1.LinkTo(transformBlock0, linkOptions);
    transformBlock0.LinkTo(actionBlock1, linkOptions);

    for (int i = 0; i <= 200; i++)
    {
        batchBlock1.Post(new VolaPoint());
    }

    batchBlock1.Complete();

    await actionBlock1.Completion;
}

现在，如果 CalculateStrangles(x) 正在返回某些内容，那么您需要 link 将最后一个转换块转换为其他内容，否则您将永远无法完成。

TPL 数据流：为什么以下阻塞？

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