【发布时间】：2014-01-10 03:06:59
【问题描述】：
我希望执行一系列任务，每个任务都有自己的超时时间。
我从这里借用了创建超时任务的扩展方法 http://blogs.msdn.com/b/pfxteam/archive/2011/11/10/10235834.aspx
所以代码在下面
public static Task TimeoutAfter(this Task task, int millisecondsTimeout)
{
// Short-circuit #1: infinite timeout or task already completed
if (task.IsCompleted || (millisecondsTimeout == Timeout.Infinite))
{
// Either the task has already completed or timeout will never occur.
// No proxy necessary.
return task;
}
// tcs.Task will be returned as a proxy to the caller
TaskCompletionSource<VoidTypeStruct> tcs = new TaskCompletionSource<VoidTypeStruct>();
// Short-circuit #2: zero timeout
if (millisecondsTimeout == 0)
{
// We've already timed out.
tcs.SetException(new TimeoutException());
return tcs.Task;
}
// Set up a timer to complete after the specified timeout period
Timer timer = new Timer(state =>
{
// Recover your state information
var myTcs = (TaskCompletionSource<VoidTypeStruct>)state;
// Fault our proxy with a TimeoutException
myTcs.TrySetException(new TimeoutException());
}, tcs, millisecondsTimeout, Timeout.Infinite);
// Wire up the logic for what happens when source task completes
task.ContinueWith(antecedent =>
{
timer.Dispose(); // Cancel the timer
MarshalTaskResults(antecedent, tcs); // Marshal results to proxy
},
CancellationToken.None, TaskContinuationOptions.ExecuteSynchronously, TaskScheduler.Default);
return tcs.Task;
}
public class Program
{
private static List<int> Output = new List<int>();
private static Random _random = new Random();
public static void LongRunningTask(string message)
{
Console.WriteLine(message);
Console.WriteLine("Managed thread Id " + Thread.CurrentThread.ManagedThreadId);
//Simulate a long running task
Thread.Sleep(TimeSpan.FromSeconds(3));
var number = _random.Next();
Console.WriteLine("Adding " + number);
Output.Add(number);
}
public static void Main(string[] args)
{
var tasks = new List<Task>();
var t1 = Task.Factory.StartNew(_ => LongRunningTask("Entering task1"),TaskCreationOptions.AttachedToParent).TimeoutAfter(10);
var t2 = Task.Factory.StartNew(_ => LongRunningTask("Entering task2"),TaskCreationOptions.AttachedToParent);
var t3 = Task.Factory.StartNew(_ => LongRunningTask("Entering task3"),TaskCreationOptions.AttachedToParent);
tasks.Add(t1);
tasks.Add(t2);
tasks.Add(t3);
try
{
Task.WaitAll(tasks.ToArray());
}
catch (Exception ex)
{
Console.WriteLine("There was an exception");
Console.WriteLine(ex.InnerException.Message);
}
Console.WriteLine("Output :");
Output.ForEach(_ => Console.WriteLine(_));
Console.ReadLine();
}
}
the output
Entering task1
Managed thread Id 10
Entering task2
Managed thread Id 11
Entering task3
Managed thread Id 14
Adding 453738994
Adding 156432981
Adding 1340619865
There was an exception
The operation has timed out.
Output :
453738994
156432981
1340619865
现在，我无法理解的是为什么即使我指定了超时并且发生了超时异常，t1 仍然完成。
我正在使用 .net 4。
编辑：
确保超时任务在超时期限后不做任何事情，即完全取消任务。
public class Program
{
private static List<int> Output = new List<int>();
private static Random _random = new Random();
public static int LongRunningTask(string message)
{
Console.WriteLine(message);
Console.WriteLine("Managed thread Id " + Thread.CurrentThread.ManagedThreadId);
//Simulate a long running task
Thread.Sleep(TimeSpan.FromSeconds(2));
var number = _random.Next();
Console.WriteLine("Adding " + number + " From thread - " + Thread.CurrentThread.ManagedThreadId);
return number;
}
public static void Main(string[] args)
{
Console.WriteLine("In Main");
Console.WriteLine("Managed thread Id " + Thread.CurrentThread.ManagedThreadId);
var cts = new CancellationTokenSource();
var tasks = new List<Task>();
var t1 = Task.Factory.StartNew(_ => LongRunningTask("Entering task1"), TaskCreationOptions.AttachedToParent)
.ContinueWith(_ => Output.Add(_.Result),cts.Token)
.TimeoutAfter(1000);
var t2 = Task.Factory.StartNew(_ => LongRunningTask("Entering task2"), TaskCreationOptions.AttachedToParent)
.ContinueWith(_ => Output.Add(_.Result));
var t3 = Task.Factory.StartNew(_ => LongRunningTask("Entering task3"), TaskCreationOptions.AttachedToParent)
.ContinueWith(_ => Output.Add(_.Result));
tasks.Add(t1);
tasks.Add(t2);
tasks.Add(t3);
try
{
Task.WaitAll(tasks.ToArray());
}
catch (Exception ex)
{
Console.WriteLine("There was an exception");
Console.WriteLine(ex.InnerException.Message);
cts.Cancel();
}
Console.WriteLine("Output :");
Output.ForEach(_ => Console.WriteLine(_));
Console.ReadLine();
}
}
输出：
In Main
Managed thread Id 9
Entering task1
Managed thread Id 10
Entering task2
Managed thread Id 11
Entering task3
Managed thread Id 13
Adding 1141027730 From thread - 10
Adding 1856518562 From thread - 13
Adding 1856518562 From thread - 11
There was an exception
The operation has timed out.
Output :
1141027730
1856518562
1856518562
【问题讨论】：
标签： .net c#-4.0 asynchronous timeout task-parallel-library