Task fromAsync timeout

本文关键字：timeout fromAsync Task | 更新日期: 2023-09-27 18:08:03

我有这段代码来发出异步HTTP请求:

    public static void MakeRequest(Uri uri, Action<RequestCallbackState> responseCallback)
    {
        WebRequest request = WebRequest.Create(uri);
        request.Proxy = null;
        Task.Factory.FromAsync<WebResponse>(request.BeginGetResponse, request.EndGetResponse, null).ContinueWith(task =>
            {
                WebResponse response = task.Result;
                Stream responseStream = response.GetResponseStream();
                responseCallback(new RequestCallbackState(response.GetResponseStream()));
                responseStream.Close();
                response.Close();
            });
    }

它工作，但我需要设置一个请求超时。我试着用请求。暂停，但似乎没有做任何事情。在此代码中是否有方法设置任务超时?

编辑添加一个新的超时回调。新代码:

    public static void MakeRequest(Uri uri, Action<RequestCallbackState> responseCallback)
    {
        WebRequest request = WebRequest.Create(uri);
        request.Proxy = null;
        IAsyncResult t = Task.Factory.FromAsync<WebResponse>(request.BeginGetResponse, request.EndGetResponse, null).ContinueWith(task =>
            {
                WebResponse response = task.Result;
                Stream responseStream = response.GetResponseStream();
                responseCallback(new RequestCallbackState(response.GetResponseStream()));
                responseStream.Close();
                response.Close();
            });
        ThreadPool.RegisterWaitForSingleObject(t.AsyncWaitHandle, new WaitOrTimerCallback(TimeoutCallback), request, 1000, true);
    }
    private static void TimeoutCallback(object state, bool timedOut)
    {
        if (timedOut)
        {
            Console.WriteLine("Timeout");
            WebRequest request = (WebRequest)state;
            if (state != null)
            {
                request.Abort();
            }
        }
    }
测试:

HttpSocket.MakeRequest(new Uri("http://www.google.comhklhlñ"), callbackState =>
    {
        if (callbackState.Exception != null)
            throw callbackState.Exception;
        Console.WriteLine(GetResponseText(callbackState.ResponseStream));
    });
Thread.Sleep(10000);

Task fromAsync timeout

来自Timeout文档:

Timeout属性对使用BeginGetResponse或BeginGetRequestStream方法发出的异步请求没有影响。

这是因为框架强制您自己处理超时。除了将FromAsync调用返回的Task传递给ThreadPool.RegisterWaitForSingleObject方法之外，您应该能够使用这里的示例代码。

编辑:

您需要将注册放在原始任务上，而不是延续上:

public static void MakeRequest(Uri uri, Action<Stream> responseCallback)
{
    WebRequest request = WebRequest.Create(uri);
    request.Proxy = null;
    const int TimeoutPeriod = 1000;
    Task<WebResponse> t = Task.Factory.FromAsync<WebResponse>(request.BeginGetResponse, request.EndGetResponse, null);
    ThreadPool.RegisterWaitForSingleObject((t as IAsyncResult).AsyncWaitHandle, TimeoutCallback, request, TimeoutPeriod, true);
    t.ContinueWith(task =>
    {
        WebResponse response = task.Result;
        Stream responseStream = response.GetResponseStream();
        responseCallback(response.GetResponseStream());
        responseStream.Close();
        response.Close();
    });
}

这对我来说很有效(如果我把超时时间设置得很短，然后点击这个，我总是会适当地超时)。

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