在使用BlockingCollection作为队列的使用者中等待异步方法 [英] awaiting async method in consumer using BlockingCollection as queue

问题描述

我正在处理一个服务器端控制台应用程序，该应用程序从多个WCF服务接收数据，对其进行一些处理，然后使用SignalR通过单个连接将结果转发到IIS服务器.

I am working on a server side console application which receives data from multiple WCF services, does some work on it and then forwards the results to an IIS server over a single connection using SignalR.

我尝试使用生产者使用者模式来实现这一点，其中WCF服务是生产者，而使用SignalR发送数据的类是使用者.对于队列，我使用了 BlockingCollection .

I tried to implement this using the producer consumer pattern where the WCF services are the producers and the class sending the data using SignalR is the consumer. For the queue I used the BlockingCollection.

但是，当使用await/async在使用者的while循环中发送数据时，卡住了，直到所有其他线程都已将数据添加到队列中为止.

However, when using await/async to send the data in the consumer's while loop gets stuck until all other threads have finished adding data to the queue.

出于测试目的，我用Task.Delay(1000).Wait();或await Task.Delay(1000);替换了实际发送数据的代码，这两个代码也都卡住了. 一个简单的Thread.Sleep(1000);似乎可以正常工作，使我认为异步代码是问题所在.

For testing purposes I have replaced the code actually sending the data with a Task.Delay(1000).Wait(); or await Task.Delay(1000); which both get stuck as well. A simple Thread.Sleep(1000); seems to work just fine, leading me to think the asynchronous code is the problem.

所以我的问题是:是否有某些因素阻止在while循环中完成异步代码?我想念什么?

So my question is: Is there something preventing the asynchronous code being completed in the while loop? What am I missing?

我正在像这样启动使用者线程:

I'm starting the consumer thread like this:

new Thread(Worker).Start();

以及消费者代码:

private void Worker()
{
    while (!_queue.IsCompleted)
    {
        IMobileMessage msg = null;
        try
        {
            msg = _queue.Take();
        }
        catch (InvalidOperationException)
        {
        }

        if (msg != null)
        {
            try
            {
                Trace.TraceInformation("Sending: {0}", msg.Name);
                Thread.Sleep(1000); // <-- works
                //Task.Delay(1000).Wait(); // <-- doesn't work
                msg.SentTime = DateTime.UtcNow;
                Trace.TraceInformation("X sent at {1}: {0}", msg.Name, msg.SentTime);
            }
            catch (Exception e)
            {
                TraceException(e);
            }
        }
    }
}

推荐答案

正如支出者正确指出的那样，BlockingCollection(顾名思义)仅用于阻塞代码，不适用于异步代码

As spender correctly pointed out, BlockingCollection (as the name implies) is intended only for use with blocking code, and does not work so well with asynchronous code.

有异步兼容的生产者/消费者队列，例如BufferBlock<T>.在这种情况下，我认为ActionBlock<T>会更好:

There are async-compatible producer/consumer queues, such as BufferBlock<T>. In this case, I would think ActionBlock<T> would be even better:

private ActionBlock<IMobileMsg> _block = new ActionBlock<IMobileMsg>(async msg =>
{
  try
  {
    Trace.TraceInformation("Sending: {0}", msg.Name);
    await Task.Delay(1000);
    msg.SentTime = DateTime.UtcNow;
    Trace.TraceInformation("X sent at {1}: {0}", msg.Name, msg.SentTime);
  }
  catch (Exception e)
  {
    TraceException(e);
  }
});

这将替换整个消耗线程和主循环.

This replaces your entire consuming thread and main loop.

这篇关于在使用BlockingCollection作为队列的使用者中等待异步方法的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！