我正在寻找实现通用方法的好主意，以使单行（或匿名委托）代码在超时时执行。
TemperamentalClass tc = new TemperamentalClass();
tc.DoSomething(); // normally runs in 30 sec. Want to error at 1 min
我正在寻找一种可以在我的代码与气质代码交互的许多地方优雅地实现的解决方案（我无法更改）。
此外，如果可能的话，我希望停止执行有问题的“超时”代码。
chilltemp
问问题
73201 次
7 回答
95
这里真正棘手的部分是通过将执行程序线程从 Action 传递回可以中止的地方来终止长时间运行的任务。我通过使用一个包装的委托来实现这一点，该委托将要杀死的线程传递到创建 lambda 的方法中的一个局部变量中。
我提交这个例子，为了你的享受。您真正感兴趣的方法是 CallWithTimeout。 这将通过中止它并吞下 ThreadAbortException 来取消长时间运行的线程：
用法：
class Program
{
static void Main(string[] args)
{
//try the five second method with a 6 second timeout
CallWithTimeout(FiveSecondMethod, 6000);
//try the five second method with a 4 second timeout
//this will throw a timeout exception
CallWithTimeout(FiveSecondMethod, 4000);
}
static void FiveSecondMethod()
{
Thread.Sleep(5000);
}
做这项工作的静态方法：
static void CallWithTimeout(Action action, int timeoutMilliseconds)
{
Thread threadToKill = null;
Action wrappedAction = () =>
{
threadToKill = Thread.CurrentThread;
try
{
action();
}
catch(ThreadAbortException ex){
Thread.ResetAbort();// cancel hard aborting, lets to finish it nicely.
}
};
IAsyncResult result = wrappedAction.BeginInvoke(null, null);
if (result.AsyncWaitHandle.WaitOne(timeoutMilliseconds))
{
wrappedAction.EndInvoke(result);
}
else
{
threadToKill.Abort();
throw new TimeoutException();
}
}
}
于 2008-11-18T16:31:14.017 回答
73
我们在生产中大量使用这样的代码：
var result = WaitFor<Result>.Run(1.Minutes(), () => service.GetSomeFragileResult());
实施是开源的，即使在并行计算场景中也能高效工作，并且作为Lokad 共享库的一部分提供
/// <summary>
/// Helper class for invoking tasks with timeout. Overhead is 0,005 ms.
/// </summary>
/// <typeparam name="TResult">The type of the result.</typeparam>
[Immutable]
public sealed class WaitFor<TResult>
{
readonly TimeSpan _timeout;
/// <summary>
/// Initializes a new instance of the <see cref="WaitFor{T}"/> class,
/// using the specified timeout for all operations.
/// </summary>
/// <param name="timeout">The timeout.</param>
public WaitFor(TimeSpan timeout)
{
_timeout = timeout;
}
/// <summary>
/// Executes the spcified function within the current thread, aborting it
/// if it does not complete within the specified timeout interval.
/// </summary>
/// <param name="function">The function.</param>
/// <returns>result of the function</returns>
/// <remarks>
/// The performance trick is that we do not interrupt the current
/// running thread. Instead, we just create a watcher that will sleep
/// until the originating thread terminates or until the timeout is
/// elapsed.
/// </remarks>
/// <exception cref="ArgumentNullException">if function is null</exception>
/// <exception cref="TimeoutException">if the function does not finish in time </exception>
public TResult Run(Func<TResult> function)
{
if (function == null) throw new ArgumentNullException("function");
var sync = new object();
var isCompleted = false;
WaitCallback watcher = obj =>
{
var watchedThread = obj as Thread;
lock (sync)
{
if (!isCompleted)
{
Monitor.Wait(sync, _timeout);
}
}
// CAUTION: the call to Abort() can be blocking in rare situations
// http://msdn.microsoft.com/en-us/library/ty8d3wta.aspx
// Hence, it should not be called with the 'lock' as it could deadlock
// with the 'finally' block below.
if (!isCompleted)
{
watchedThread.Abort();
}
};
try
{
ThreadPool.QueueUserWorkItem(watcher, Thread.CurrentThread);
return function();
}
catch (ThreadAbortException)
{
// This is our own exception.
Thread.ResetAbort();
throw new TimeoutException(string.Format("The operation has timed out after {0}.", _timeout));
}
finally
{
lock (sync)
{
isCompleted = true;
Monitor.Pulse(sync);
}
}
}
/// <summary>
/// Executes the spcified function within the current thread, aborting it
/// if it does not complete within the specified timeout interval.
/// </summary>
/// <param name="timeout">The timeout.</param>
/// <param name="function">The function.</param>
/// <returns>result of the function</returns>
/// <remarks>
/// The performance trick is that we do not interrupt the current
/// running thread. Instead, we just create a watcher that will sleep
/// until the originating thread terminates or until the timeout is
/// elapsed.
/// </remarks>
/// <exception cref="ArgumentNullException">if function is null</exception>
/// <exception cref="TimeoutException">if the function does not finish in time </exception>
public static TResult Run(TimeSpan timeout, Func<TResult> function)
{
return new WaitFor<TResult>(timeout).Run(function);
}
}
这段代码还是有问题的，你可以试试这个小测试程序：
static void Main(string[] args) {
// Use a sb instead of Console.WriteLine() that is modifying how synchronous object are working
var sb = new StringBuilder();
for (var j = 1; j < 10; j++) // do the experiment 10 times to have chances to see the ThreadAbortException
for (var ii = 8; ii < 15; ii++) {
int i = ii;
try {
Debug.WriteLine(i);
try {
WaitFor<int>.Run(TimeSpan.FromMilliseconds(10), () => {
Thread.Sleep(i);
sb.Append("Processed " + i + "\r\n");
return i;
});
}
catch (TimeoutException) {
sb.Append("Time out for " + i + "\r\n");
}
Thread.Sleep(10); // Here to wait until we get the abort procedure
}
catch (ThreadAbortException) {
Thread.ResetAbort();
sb.Append(" *** ThreadAbortException on " + i + " *** \r\n");
}
}
Console.WriteLine(sb.ToString());
}
}
有一个竞争条件。很明显，在调用该方法后会引发 ThreadAbortException WaitFor<int>.Run()。我没有找到解决此问题的可靠方法，但是通过相同的测试，我无法重现TheSoftwareJedi接受的答案的任何问题。
于 2009-06-13T11:54:11.350 回答
15
好吧，你可以用委托做事（BeginInvoke，用回调设置一个标志——原始代码等待那个标志或超时）——但问题是很难关闭正在运行的代码。例如，杀死（或暂停）一个线程是危险的......所以我认为没有一种简单的方法可以稳健地做到这一点。
我会发布这个，但请注意它并不理想 - 它不会停止长时间运行的任务，并且在失败时不会正确清理。
static void Main()
{
DoWork(OK, 5000);
DoWork(Nasty, 5000);
}
static void OK()
{
Thread.Sleep(1000);
}
static void Nasty()
{
Thread.Sleep(10000);
}
static void DoWork(Action action, int timeout)
{
ManualResetEvent evt = new ManualResetEvent(false);
AsyncCallback cb = delegate {evt.Set();};
IAsyncResult result = action.BeginInvoke(cb, null);
if (evt.WaitOne(timeout))
{
action.EndInvoke(result);
}
else
{
throw new TimeoutException();
}
}
static T DoWork<T>(Func<T> func, int timeout)
{
ManualResetEvent evt = new ManualResetEvent(false);
AsyncCallback cb = delegate { evt.Set(); };
IAsyncResult result = func.BeginInvoke(cb, null);
if (evt.WaitOne(timeout))
{
return func.EndInvoke(result);
}
else
{
throw new TimeoutException();
}
}
于 2008-11-18T16:06:17.530 回答
13
对 Pop Catalin 的最佳答案的一些小改动：
- 函数而不是动作
- 超时值错误引发异常
- 在超时的情况下调用 EndInvoke
添加了重载以支持信号工作者取消执行：
public static T Invoke<T> (Func<CancelEventArgs, T> function, TimeSpan timeout) {
if (timeout.TotalMilliseconds <= 0)
throw new ArgumentOutOfRangeException ("timeout");
CancelEventArgs args = new CancelEventArgs (false);
IAsyncResult functionResult = function.BeginInvoke (args, null, null);
WaitHandle waitHandle = functionResult.AsyncWaitHandle;
if (!waitHandle.WaitOne (timeout)) {
args.Cancel = true; // flag to worker that it should cancel!
/* •————————————————————————————————————————————————————————————————————————•
| IMPORTANT: Always call EndInvoke to complete your asynchronous call. |
| http://msdn.microsoft.com/en-us/library/2e08f6yc(VS.80).aspx |
| (even though we arn't interested in the result) |
•————————————————————————————————————————————————————————————————————————• */
ThreadPool.UnsafeRegisterWaitForSingleObject (waitHandle,
(state, timedOut) => function.EndInvoke (functionResult),
null, -1, true);
throw new TimeoutException ();
}
else
return function.EndInvoke (functionResult);
}
public static T Invoke<T> (Func<T> function, TimeSpan timeout) {
return Invoke (args => function (), timeout); // ignore CancelEventArgs
}
public static void Invoke (Action<CancelEventArgs> action, TimeSpan timeout) {
Invoke<int> (args => { // pass a function that returns 0 & ignore result
action (args);
return 0;
}, timeout);
}
public static void TryInvoke (Action action, TimeSpan timeout) {
Invoke (args => action (), timeout); // ignore CancelEventArgs
}
于 2009-05-15T15:11:33.990 回答
10
这就是我的做法：
public static class Runner
{
public static void Run(Action action, TimeSpan timeout)
{
IAsyncResult ar = action.BeginInvoke(null, null);
if (ar.AsyncWaitHandle.WaitOne(timeout))
action.EndInvoke(ar); // This is necesary so that any exceptions thrown by action delegate is rethrown on completion
else
throw new TimeoutException("Action failed to complete using the given timeout!");
}
}
于 2008-11-18T17:04:24.480 回答
7
我现在刚刚把它淘汰了，所以它可能需要一些改进，但会做你想做的。这是一个简单的控制台应用程序，但演示了所需的原则。
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading;
namespace TemporalThingy
{
class Program
{
static void Main(string[] args)
{
Action action = () => Thread.Sleep(10000);
DoSomething(action, 5000);
Console.ReadKey();
}
static void DoSomething(Action action, int timeout)
{
EventWaitHandle waitHandle = new EventWaitHandle(false, EventResetMode.ManualReset);
AsyncCallback callback = ar => waitHandle.Set();
action.BeginInvoke(callback, null);
if (!waitHandle.WaitOne(timeout))
throw new Exception("Failed to complete in the timeout specified.");
}
}
}
于 2008-11-18T16:13:54.893 回答
2
使用 Thread.Join(int timeout) 怎么样？
public static void CallWithTimeout(Action act, int millisecondsTimeout)
{
var thread = new Thread(new ThreadStart(act));
thread.Start();
if (!thread.Join(millisecondsTimeout))
throw new Exception("Timed out");
}
于 2009-08-12T20:00:40.017 回答