TPL 數據流 C# 等待所有鏈接塊完成

Question

我正在使用 TPL Dataflow 來構建管道。 此管道應在邏輯上執行以下操作：

1. 從處理多個數據項開始——假設它是pollingBlock 。
2. 如果滿足某些條件，則將其中一項（已滿足條件）傳遞給某個塊以進行進一步監控，假設它是monitoringBlock 。 每個monitoringBlock只能容納 1 個 item，但有多個monitoringBlocks 。
3. pollingBlock應該繼續處理所有項目，包括以一段while (true)方式發布的項目。
4. 被占用的monitoringBlocks塊不應該接受任何其他消息，並且這些消息應該被刪除而無需進一步處理。
5. 在monitoringBlock中進行一些處理后，消息應該被標記為完成或者轉移到下一個塊進行處理，這個下一個塊是processingBlock

一個簡短的示例：

public Task ExecutePipeline()
{
    var block = CreatePollingPipeline();
    block.Post((_serviceOne, _serviceTwo));

    block.Complete();
    return block.Completion;
}

public ActionBlock<(IServiceOne serviceOne, IServiceTwo serviceTwo)> CreatePollingPipeline()
{
    var pollingAlertHolder = new BufferBlock<(string input1, string input2)>();

    var pollingBlock = new ActionBlock<(IServiceOne serviceOne, IServiceTwo serviceTwo)>(services =>
    {
        while (true)
        {
            Console.WriteLine("Posting to alert block");
            pollingAlertHolder.Post(("INP1", "INPVAL"));
            Thread.Sleep(2000);

            Console.WriteLine("Posting to alert block");
            pollingAlertHolder.Post(("INP1", "INPVAL"));
            Thread.Sleep(2000);

            Console.WriteLine("Posting to alert block");
            pollingAlertHolder.Post(("INP2", "INPVAL2"));
            Thread.Sleep(2000);

            Console.WriteLine("Posting to alert block");
            pollingAlertHolder.Post(("INP1", "INPVAL"));
            Thread.Sleep(2000);

            Console.WriteLine("Posting to alert block");
            pollingAlertHolder.Post(("INP1", "INPVAL"));
            Thread.Sleep(2000);

            Console.WriteLine("Posting to alert block");
            pollingAlertHolder.Post(("INP2", "INPVAL2"));
            Thread.Sleep(2000);
        }
    });

    var monitoringBlock = new TransformBlock<(string input1, string input2), (string input1, string input2)>(inputs =>
        {
            Console.WriteLine("monitoringBlock started");
            Thread.Sleep(5000);
            Console.WriteLine("monitoringBlock completed");

            return (inputs.input1, inputs.input2);
        },
        new ExecutionDataflowBlockOptions { MaxDegreeOfParallelism = 1, BoundedCapacity = 1 });

    pollingAlertHolder.LinkTo(monitoringBlock, new DataflowLinkOptions() { PropagateCompletion = true },
        inputs => inputs.input1 == "INP1" && inputs.input2 == "INPVAL");
    pollingAlertHolder.LinkTo(DataflowBlock.NullTarget<(string input1, string input2)>());

    var processingBlock = new ActionBlock<(string input1, string input2)>(i =>
    {
        Console.WriteLine("processingBlock started");
        Thread.Sleep(2000);
        Console.WriteLine("processingBlock completed");
    }, new ExecutionDataflowBlockOptions { MaxDegreeOfParallelism = 1, BoundedCapacity = 1 });
    monitoringBlock.LinkTo(processingBlock, new DataflowLinkOptions { PropagateCompletion = true });


    return pollingBlock;
}

我的問題是如何在鏈接的processingBlock完成其工作之前保持monitoringBlock被占用？ 在消息完成完整處理周期之前，我不希望將任何項目發布到monitoringBlock 。

Answer 1

正如評論中已經提到的，您可以簡單地將monitoringBlock和processingBlock的邏輯封裝在一個塊中，例如，您可以通過預定義的Datablock.Encapsulate方法來實現。

但是，如果您不想這樣做，您可以使用AutoResetEvent或類似的抽象，您的代碼可能是這樣的：

AutoResetEvent dataflowEvent = new AutoResetEvent(true);
var bufferBlock = new ActionBLock<(string input1, string input2)>(i =>
{
    dataflowEvent.WaitOne();
    monitoringBlock.Post(i);
});
var monitoringBlock = new TransformBlock<(string input1, string input2), (string input1, string input2)>(inputs =>
    {
        Console.WriteLine("monitoringBlock started");
        Thread.Sleep(5000);
        Console.WriteLine("monitoringBlock completed");

        dataflowEvent.Set();
        return (inputs.input1, inputs.input2);
    },
    new ExecutionDataflowBlockOptions { MaxDegreeOfParallelism = 1, BoundedCapacity = 1 });