c# - HttpListener 的多线程应答

Question

我有一个执行了很长时间的单线程进程。我需要多个用户有权执行此过程，我选择 http 协议(protocol)来管理调用。

自然地，当一个进程在工作时，其他人应该等到它完成。如果进程可用，它就会执行。如果不是，则发送 BUSY 应答。

这里是实现:

using System;
using System.Net;
using System.Reflection;
using System.Runtime.InteropServices;
using System.Threading;
using System.Threading.Tasks;

namespace simplehttp
{
    class Program
    {
        private static System.AsyncCallback task;
        private static System.Threading.ManualResetEvent mre = new System.Threading.ManualResetEvent(false);// Notifies one or more waiting threads that an event has occurred. 
        private static HttpListenerContext workingContext = null;

        public static bool isBackgroundWorking()
        {
            return mre.WaitOne(0);
        }
        static void Main(string[] args)
        {
            new Thread(() =>
            {
                Thread.CurrentThread.IsBackground = true;
                while (true)
                {
                    Console.WriteLine("    waitOne " + isBackgroundWorking());
                    mre.WaitOne(); // Blocks the current thread until the current WaitHandle receives a signal.
                    Console.WriteLine("    do job" + " [" + Thread.CurrentThread.Name + ":" + Thread.CurrentThread.ManagedThreadId + " ]\n");
                    HttpListenerRequest request = workingContext.Request;
                    HttpListenerResponse response = workingContext.Response;
                    string responseString = "WORK " + DateTime.Now ;
                    byte[] buffer = System.Text.Encoding.UTF8.GetBytes(responseString);
                    response.ContentLength64 = buffer.Length;
                    System.IO.Stream output = response.OutputStream;
                    Thread.Sleep(10000);
                    output.Write(buffer, 0, buffer.Length);
                    output.Close();
                    Console.WriteLine("    " + responseString + "\t" + DateTime.Now);
                    workingContext = null;
                    mre.Reset(); // Sets the state of the event to nonsignaled, causing threads to block.
                }
            }).Start();

            // Create a listener.
            HttpListener listener = new HttpListener();

            listener.Prefixes.Add("http://localhost:6789/index/");
            listener.Start();
            Console.WriteLine("Listening..." + " [" + Thread.CurrentThread.Name + ":" + Thread.CurrentThread.ManagedThreadId + " ]\n");

            task = new AsyncCallback(ListenerCallback);

            IAsyncResult resultM = listener.BeginGetContext(task,listener);
            Console.WriteLine("Waiting for request to be processed asyncronously.");

            Console.ReadKey();
            Console.WriteLine("Request processed asyncronously.");
            listener.Close();
        }

        private static void ListenerCallback(IAsyncResult result)
        {
            HttpListener listener = (HttpListener) result.AsyncState;

            //If not listening return immediately as this method is called one last time after Close()
            if (!listener.IsListening)
                return;

            HttpListenerContext context = listener.EndGetContext(result);
            listener.BeginGetContext(task, listener);

            if (workingContext == null && !isBackgroundWorking())
            {
                // Background work
                workingContext = context;
                mre.Set(); //Sets the state of the event to signaled, allowing one or more waiting threads to proceed.
            }
            else
            {
            HttpListenerRequest request = context.Request;
            HttpListenerResponse response = context.Response;
            string responseString = "BUSY "+ DateTime.Now + " [" + Thread.CurrentThread.Name + ":" + Thread.CurrentThread.ManagedThreadId;
            byte[] buffer = System.Text.Encoding.UTF8.GetBytes(responseString);
            response.ContentLength64 = buffer.Length;
            System.IO.Stream output = response.OutputStream;
            output.Write(buffer, 0, buffer.Length);
            output.Close();
            Console.WriteLine(responseString + "\t" + DateTime.Now);
            }
        }
    }
}

为了测试，我进行了 2 个 http 调用。我希望有 2 个不同的答案 WORK 和 BUSY。但是我看到第二个请求先等待完成然后执行。

      waitOne False
Listening... [:10 ]

Waiting for request to be processed asyncronously.
      do job [:11 ]

      WORK 1/24/2016 10:34:01 AM  1/24/2016 10:34:11 AM
      waitOne False
      do job [:11 ]

      WORK 1/24/2016 10:34:11 AM  1/24/2016 10:34:21 AM
      waitOne False

我对它应该如何工作的理解有什么问题？

更新(SO 不鼓励太多评论):我的代码看起来很尴尬，因为它是真实过程的复制。在“我的”应用程序中，工作进程是主进程，它在某些特定时刻“有礼貌”地运行嵌入式 C# 代码。因此，我无法运行新任务来处理请求，而且它必须是异步的，因为工作进程会完成自己的工作，并且仅在数据可用时调用从属代码段来通知客户端。它是异步的，因为代码被调用并且应该尽快完成，否则它将阻塞主应用程序。我将尝试通过同步调用添加额外的线程，看看它是否会影响情况。

此示例中未使用调试器，以免干扰打印到控制台的实时进程和时间戳。调试非常好，也是必要的，但在这种情况下，我尝试用输出代替，以避免在同步/等待场景中出现额外的参与者。

应用程序本身并不是繁重的对话。 1-3个客户很少向主应用询问答案。 http协议(protocol)用于方便而不是用于繁重或经常的对话。似乎某些浏览器(如 IE)运行良好(Windows 到 Windows 对话？)，而某些浏览器(如 Chrome)(更多系统不可知论者)复制了我的应用程序行为。查看时间戳，Chrome、IE、IE、Chrome 和最后一个 Chrome 仍然进入 WORK 进程。顺便说一句，每个对话建议都会更改代码，现在在检索到上一个请求后会立即发出新请求。

    HttpListenerContext context = listener.EndGetContext(result);
    listener.BeginGetContext(task, listener); 

此外，根据建议，我更改了对 syncroniuos 的异步调用，结果仍然相同

private static void ListenerCallback(IAsyncResult result)
{
    HttpListener listener = (HttpListener) result.AsyncState;

    //If not listening return immediately as this method is called one last time after Close()
    if (!listener.IsListening)
        return;

    HttpListenerContext context = listener.EndGetContext(result);

    while (true)
    {
        if (workingContext == null && !isBackgroundWorking())
        {
            // Background work
            workingContext = context;
            mre.Set(); //Sets the state of the event to signaled, allowing one or more waiting threads to proceed.
        }
        else
        {
            HttpListenerRequest request = context.Request;
            HttpListenerResponse response = context.Response;
            string responseString = "BUSY " + DateTime.Now + " [" + Thread.CurrentThread.Name + ":" +
                                    Thread.CurrentThread.ManagedThreadId;
            byte[] buffer = System.Text.Encoding.UTF8.GetBytes(responseString);
            response.ContentLength64 = buffer.Length;
            System.IO.Stream output = response.OutputStream;
            output.Write(buffer, 0, buffer.Length);
            output.Close();
            Console.WriteLine(responseString + "\t" + DateTime.Now);
        }
        context=listener.GetContext();
    }
}

Answer 1

发布的代码完全可以正常工作:

无法重现。我想这可以回答问题，因为显然您错误地驱动了测试工作负载。我通过反复单击 Fiddler composer 发送按钮来驱动它。

不过，感谢您发布可执行代码。我应该早点尝试!