我注意到,当我使用 System.Net.HttpClient
时,超时时间很短,它有时可能会导致进程崩溃,即使它包含在 try-catch block 中也是如此。这是一个重现此内容的简短程序。
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,并出现以下异常:
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()
稍微深入一点,似乎当 HttpClient
在创建相关的 ServicePoint
之前中止请求时,HttpWebRequest
会尝试创建 ServicePoint
,通过 ServicePointManager.FindServicePoint
,抛出 RequestCanceled。由于这个异常是在试图取消请求的线程中抛出的,它没有被捕获,进程就死掉了。
我错过了什么吗?你遇到过这个问题吗?
最佳答案
HttpWebRequest.Abort()
在后台/计时器线程上抛出异常。与HttpClient的Task管理无关。
HttpWebRequest.Abort()
的异常应该在 .NET 4.5 GDR1 中修复。
http://support.microsoft.com/kb/2750149
http://support.microsoft.com/kb/2750147
关于c# - 将 HttpClient 设置为太短的超时会导致进程崩溃,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/15363536/