Question

我有两种方法：

public void Stop(bool immediate)
{
    Logger.Log(LogLevel.Debug, "Shutdown detected. Immediate: " + immediate);
    Shutdown();
    Logger.Log(LogLevel.Debug, "Unregistering");
    HostingEnvironment.UnregisterObject(this);
}

public void Shutdown()
{
    Logger.Log(LogLevel.Debug, "Preparing to stop UploadQueue");
    IsProcessing = false;

     //Set tasks to cancel to prevent queued tasks from parsing
     _cancellationTokenSource.Cancel();

     Logger.Log(LogLevel.Debug, "Waiting for " + _workerTasks.Count + " tasks to finish or cancel.");
     //Wait for tasks to finish
     Task.WaitAll(_workerTasks.Values.ToArray());

     Logger.Log(LogLevel.Debug, "Stopped UploadQueue");
}

该类正在使用IRegisteredObject接口来接收关闭通知。在我的日志中，我得到了这个：

2014-07-18 15:30:55,913,DEBUG,Shutdown detected. Immediate: False
2014-07-18 15:30:55,913,DEBUG,Preparing to stop UploadQueue
2014-07-18 15:30:55,913,DEBUG,Waiting for 35 tasks to finish or cancel.
...
bunch of stuff
...
2014-07-18 15:31:28,471,DEBUG,Shutdown detected. Immediate: True
2014-07-18 15:31:28,471,DEBUG,Preparing to stop UploadQueue
2014-07-18 15:31:28,471,DEBUG,Waiting for 0 tasks to finish or cancel.
2014-07-18 15:31:28,471,DEBUG,Stopped UploadQueue
2014-07-18 15:31:28,471,DEBUG,Unregistering

为什么第一次没有进入Logger.Log(LogLevel.Debug, "Stopped UploadQueue");？它肯定似乎取消了任务并让正在运行的任务完成。（任务检查在运行之前是否取消了，否则就行了）。

Answer 1

来自Task.WaitAll：

<强> AggregationException：

至少有一个任务实例被取消 - 或者 - 在执行至少一个Task实例期间抛出了异常。如果任务被取消，则AggregateException在其InnerExceptions集合中包含OperationCanceledException。

您正在通过_cancellationTokenSource.Cancel();取消您的任务，我认为这导致其中至少有一人抛出异常。您可能会在更高级别的堆栈框架中捕获它并忽略它。在try-catch块中包装Task.WaitAll：

public void Shutdown()
{
    Logger.Log(LogLevel.Debug, "Preparing to stop UploadQueue");
    IsProcessing = false;

    //Set tasks to cancel to prevent queued tasks from parsing
    _cancellationTokenSource.Cancel();

    Logger.Log(LogLevel.Debug, "Waiting for " + _workerTasks.Count + " tasks to finish or cancel.");

     try
     {
         //Wait for tasks to finish
         Task.WaitAll(_workerTasks.Values.ToArray());

         Logger.Log(LogLevel.Debug, "Stopped UploadQueue");
     }
     catch (AggregationException e)
     {
         // Recover from the exception
     }
}

IIS 7.5应用程序池回收不让方法完成

1 个答案: