IIS 7.5 应用程序池回收不让方法完成

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

为什么不是第一次到达Logger.Log(LogLevel.Debug, "Stopped UploadQueue");？它似乎确实取消了任务并让正在运行的任务完成。 （任务在运行前检查它是否被取消，否则就是这样）。

Answer 1

来自Task.WaitAll：

聚合异常：

至少有一个 Task 实例被取消 - 或 - 在至少一个 Task 实例的执行过程中引发了异常。如果任务被取消，则 AggregateException 在其 InnerExceptions 集合中包含一个 OperationCanceledException。

您正在通过_cancellationTokenSource.Cancel(); 取消您的任务，我认为这至少会导致其中一个引发异常。您可能会在更高级别的堆栈帧中捕获它并忽略它。将 Task.WaitAll 包裹在 try-catch 块中：

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
     }
}