c# - 将HttpClient设置为太短的超时崩溃过程

我注意到，当我在短时间内使用System.Net.HttpClient时，即使将它包装在try-catch块中，有时也会使该过程崩溃。这是一个简短的程序来重现此内容。

public static void Main(string[] args)
{
    var tasks = new List<Task>();
    for (int i = 0; i < 1000; i++)
    {
        tasks.Add(MakeHttpClientRequest());
    }
    Task.WaitAll(tasks.ToArray());

}

private async static Task MakeHttpClientRequest()
{
    var httpClient = new HttpClient { Timeout = TimeSpan.FromMilliseconds(1) };
    var request = "whatever";
    try
    {
        HttpResponseMessage result =
            await httpClient.PostAsync("http://www.flickr.com/services/rest/?method=flickr.test.echo&format=json&api_key=766c0ac7802d55314fa980727f747710",
                                 new StringContent(request));
        await result.Content.ReadAsStringAsync();
    }
    catch (Exception x)
    {
        Console.WriteLine("Error occurred but it is swallowed: " + x);
    }
}

运行此命令将使进程崩溃，但以下异常除外:

Unhandled Exception: System.AggregateException: One or more errors occurred. ---> System.Net.WebException: The request was canceled
   at System.Net.ServicePointManager.FindServicePoint(Uri address, IWebProxy proxy, ProxyChain& chain, HttpAbortDelegate& abortDelegate, Int32& abortState)
   at System.Net.HttpWebRequest.FindServicePoint(Boolean forceFind)
   at System.Net.HttpWebRequest.get_ServicePoint()
   at System.Net.AuthenticationState.PrepareState(HttpWebRequest httpWebRequest)
   at System.Net.AuthenticationState.ClearSession(HttpWebRequest httpWebRequest)
   at System.Net.HttpWebRequest.ClearAuthenticatedConnectionResources()
   at System.Net.HttpWebRequest.Abort(Exception exception, Int32 abortState)
   at System.Net.HttpWebRequest.Abort()
   at System.Net.Http.HttpClientHandler.OnCancel(Object state)
   at System.Threading.CancellationCallbackInfo.ExecutionContextCallback(Object obj)
   at System.Threading.ExecutionContext.RunInternal(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean preserveSyncCtx)
   at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean preserveSyncCtx)
   at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state)
   at System.Threading.CancellationCallbackInfo.ExecuteCallback()
   at System.Threading.CancellationTokenSource.CancellationCallbackCoreWork(CancellationCallbackCoreWorkArguments args)
   at System.Threading.CancellationTokenSource.ExecuteCallbackHandlers(Boolean throwOnFirstException)
   --- End of inner exception stack trace ---
   at System.Threading.CancellationTokenSource.ExecuteCallbackHandlers(Boolean throwOnFirstException)
   at System.Threading.CancellationTokenSource.NotifyCancellation(Boolean throwOnFirstException)
   at System.Threading.CancellationTokenSource.TimerCallbackLogic(Object obj)
   at System.Threading.TimerQueueTimer.CallCallbackInContext(Object state)
   at System.Threading.ExecutionContext.RunInternal(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean preserveSyncCtx)
   at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean preserveSyncCtx)
   at System.Threading.TimerQueueTimer.CallCallback()
   at System.Threading.TimerQueueTimer.Fire()
   at System.Threading.TimerQueue.FireNextTimers()
   at System.Threading.TimerQueue.AppDomainTimerCallback()

仔细研究一下，似乎在创建相关HttpClient之前ServicePoint中止请求时，HttpWebRequest尝试通过ServicePoint创建ServicePointManager.FindServicePoint，这将引发RequestCanceled。由于在试图取消请求的线程中引发了此异常，因此未捕获该异常，并且进程终止。

我想念什么吗？你遇到这个问题了吗？

最佳答案

HttpWebRequest.Abort()在后台/计时器线程上引发异常。这与HttpClient的任务管理无关。
HttpWebRequest.Abort()中的异常应在.NET 4.5 GDR1中修复。
http://support.microsoft.com/kb/2750149
http://support.microsoft.com/kb/2750147

关于c# - 将HttpClient设置为太短的超时崩溃过程，我们在Stack Overflow上找到一个类似的问题：https://stackoverflow.com/questions/15363536/