TPL 数据流：为什么会出现以下阻塞？

Question

Why is as a call to Run() blocking and doesn't return?

It correclty prints the following output, which makes sense. As I have initialized the BatchBlock() with a size of 170 and create 200 volapoint objects. But why does it not return?

ConvertToVolaSurface 
ConvertToVolaSurface 
CalculateStrangles
CalculateStrangles

This is the code snippet i am working with

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

Your last block is a TransformBlock , transform blocks have an output buffer that must be empty for them to Complete . Change your last block to an ActionBlock and await it's completion to not block the calling thread.

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;
}

Now if CalculateStrangles(x) is returning something then you need to link that last transform block to something else otherwise you'll never complete.