对.net中的服务使用Task.WaitAll()的问题

本文关键字：WaitAll 问题 Task net 服务 | 更新日期: 2023-09-27 18:19:16

我有一个OnStart()方法的服务:

protected override void OnStart(string[] args)
{
  this.manager.StartManager();
  this.log.LogEvent(this.id.ToString(), string.Format(CultureInfo.InvariantCulture, "System"), string.Format(CultureInfo.InvariantCulture, "Service started"));
}

和OnStop()方法:

protected override void OnStop()
{      
  this.manager.CancellationTokenSource.Cancel();      
  this.log.LogEvent(this.id.ToString(), string.Format(CultureInfo.InvariantCulture, "System"), string.Format(CultureInfo.InvariantCulture, "Service stopped"));
}

StartManager()方法实现如下:

public void StartManager()
{
    foreach (var reportGeneratorThread in this.ReportGenerators)
    {                
        reportGeneratorThread.Start();
        Thread.Sleep(1000);
    }
    try
    { 
        Task.WaitAll(this.Tasks.ToArray());
    }
    catch (AggregateException e)
    {
        foreach (var v in e.InnerExceptions)
            {
                var taskException = v as TaskCanceledException;
                if (v != taskException)
                {
                    foreach (var reportGenerator in this.ReportGenerators)
                    {
                        if (reportGenerator.Task.IsFaulted)
                        {
                            this.logger.LogEvent(this.Id.ToString(), string.Format(CultureInfo.InvariantCulture, "System"), string.Format(CultureInfo.InvariantCulture, "Unhandled exception from Task " + reportGenerator.Task.Id));                             
                            ReportGeneratorThread faultedReportGeneratorThread = this.GetThreadById(reportGenerator.Task.Id);
                            var index = this.ReportGenerators.FindIndex(t => t.Equals(faultedReportGeneratorThread));
                            this.DisposeFaultedThread(faultedReportGeneratorThread, index);                           
                            this.ReportGenerators[index].Start();    
                            this.logger.LogDebug(string.Format(CultureInfo.InvariantCulture, "Faulted Task, and instance of ReportGeneratorThread is recreated and corresponding task is started"));
                            break;
                        }
                    }
                }
                else if (taskException != null)
                {
                    this.logger.LogEvent(this.Id.ToString(), string.Format(CultureInfo.InvariantCulture, "System"), string.Format(CultureInfo.InvariantCulture, "Task " + taskException.Task.Id + " has thrown a Task Canceled Exception"));
                }
            }
    }
}

问题发生在我的StartManager()方法中，因为reportGeneratorThread.Start()方法正在启动一个任务，该任务在while循环中不断生成报告，该任务只能在抛出取消令牌时中止，并且我将其抛出在我的服务OnStop()方法中。因此，当我测试我的服务时，程序无法到达Task.WaitAll()以外的地方，这阻止了我完成OnStart()方法，并且我收到以下错误:

 Error 1053: the service did not respond to the start or control request in a timely fashion

我仍然需要管理我的任务，所以我实际上需要task . waitall()方法，但我也需要修复这个问题。在这种情况下，我如何完成OnStart()方法?不改变代码结构的最佳方法是什么?

添加更多代码:

这是我的任务调用的方法:

 private void DoWork()
    {
        while (this.Running)
        {
            this.GenerateReport();
            Thread.Sleep(Settings.Default.DefaultSleepDelay);
        }
        this.log.LogDebug(string.Format(CultureInfo.InvariantCulture, "Worker thread stopping."));
    }

和GenerateReport()方法:如果服务请求取消，则调用Stop()方法。这个方法抛出TaskCancelledException异常。

 public void GenerateReport()
    {
        if (this.cancellationToken.IsCancellationRequested)
        {
            this.Stop();
        }
        var didwork = false;
        try
        {
            didwork = this.reportGenerator.GenerateReport(this.getPermission, this.TaskId);
        }
        catch (Exception e)
        {
            this.log.LogError(ReportGenerator.CorrelationIdForPickingReport, string.Format(CultureInfo.InvariantCulture, "System"), string.Format(CultureInfo.InvariantCulture, "Error during report generation."), 0, e);
        }
        finally
        {
            if (!didwork)
            {
               Thread.Sleep(Settings.Default.ReportGenerationInterval);
            }
        }
    }

对.net中的服务使用Task.WaitAll()的问题

如果没有一个好的，最小的， 完整的代码示例来清楚地说明你的问题，很难确切地理解代码在做什么。至少有一些我一眼就能看到的奇怪的东西:

    你的方法旨在重新启动一个报告生成器线程。但据我所知，它只能重新启动一个。如果你以后有更多的错误，没有代码等待检测和处理它。
  1. 使用WaitAll()将阻止代码检测到甚至一个故障，直到所有任务完成。因此，它们要么都需要在重启之前出现故障，要么直到你真正停止服务并取消任务时才会检测到故障。
  2. 只有当taskException为null时，v != taskException才为真。所以在我看来，稍后检查它是非空的是毫无意义的。
  3. 我不明白在开始每个任务之间睡1秒有什么意义。

所以我不确定有可能知道修复所有这些代码的最佳方法是什么。也就是说，当前的问题似乎很清楚:您的OnStart()方法在设计上需要及时返回，但您当前的实现无法做到这一点。这个基本问题似乎是可以解决的，通过使StartManager()方法成为async方法，并使用await将控制权返回给调用者，直到发生一些有趣的事情。它可能看起来像这样:

public async Task StartManager()
{
    foreach (var reportGeneratorThread in this.ReportGenerators)
    {                
        reportGeneratorThread.Start();
        Thread.Sleep(1000);
    }
    try
    { 
        await Task.WhenAll(this.Tasks.ToArray());
    }
    catch (AggregateException e)
    {
        foreach (var v in e.InnerExceptions)
            {
                var taskException = v as TaskCanceledException;
                if (v != taskException)
                {
                    foreach (var reportGenerator in this.ReportGenerators)
                    {
                        if (reportGenerator.Task.IsFaulted)
                        {
                            this.logger.LogEvent(this.Id.ToString(), string.Format(CultureInfo.InvariantCulture, "System"), string.Format(CultureInfo.InvariantCulture, "Unhandled exception from Task " + reportGenerator.Task.Id));                             
                            ReportGeneratorThread faultedReportGeneratorThread = this.GetThreadById(reportGenerator.Task.Id);
                            var index = this.ReportGenerators.FindIndex(t => t.Equals(faultedReportGeneratorThread));
                            this.DisposeFaultedThread(faultedReportGeneratorThread, index);                           
                            this.ReportGenerators[index].Start();    
                            this.logger.LogDebug(string.Format(CultureInfo.InvariantCulture, "Faulted Task, and instance of ReportGeneratorThread is recreated and corresponding task is started"));
                            break;
                        }
                    }
                }
                else if (taskException != null)
                {
                    this.logger.LogEvent(this.Id.ToString(), string.Format(CultureInfo.InvariantCulture, "System"), string.Format(CultureInfo.InvariantCulture, "Task " + taskException.Task.Id + " has thrown a Task Canceled Exception"));
                }
            }
    }
}
然后你可以像这样从OnStart()调用它: 
protected override void OnStart(string[] args)
{
  // Save the returned Task in a local, just as a hack
  // to suppress the compiler warning about not awaiting the call.
  // Alternatively, store the Task object somewhere and actually
  // do something useful with it.
  var _ = this.manager.StartManager();
  this.log.LogEvent(this.id.ToString(), string.Format(CultureInfo.InvariantCulture, "System"), string.Format(CultureInfo.InvariantCulture, "Service started"));
}

请注意，上面建议的更改没有解决我提到的任何奇怪之处。在我看来，该方法的更有用的实现可能看起来像这样:

public async Task StartManager()
{
    foreach (var reportGeneratorThread in this.ReportGenerators)
    {                
        reportGeneratorThread.Start();
    }
    while (true)
    {
        try
        { 
            Task task = await Task.WhenAny(this.Tasks.ToArray());
            if (task.IsFaulted)
            {
                // Unpack the exception. Alternatively, you could just retrieve the
                // AggregateException directly from task.Exception and process it
                // exactly as in the original code (i.e. enumerate the
                // AggregateException.InnerExceptions collection). Note that in
                // that case, you will see only a single exception in the
                // InnerExceptions collection. To detect exceptions in additional
                // tasks, you would need to await them as well. Fortunately,
                // this will happen each time you loop back and call Task.WhenAny()
                // again, since all the tasks are in the Tasks collection being
                // passed to WhenAny().
                await task;
            }
        }
        catch (Exception v)
        {
            var taskException = v as TaskCanceledException;
            if (v != taskException)
            {
                foreach (var reportGenerator in this.ReportGenerators)
                {
                    if (reportGenerator.Task.IsFaulted)
                    {
                        this.logger.LogEvent(this.Id.ToString(), string.Format(CultureInfo.InvariantCulture, "System"), string.Format(CultureInfo.InvariantCulture, "Unhandled exception from Task " + reportGenerator.Task.Id));                             
                        ReportGeneratorThread faultedReportGeneratorThread = this.GetThreadById(reportGenerator.Task.Id);
                        var index = this.ReportGenerators.FindIndex(t => t.Equals(faultedReportGeneratorThread));
                        this.DisposeFaultedThread(faultedReportGeneratorThread, index);                           
                        this.ReportGenerators[index].Start();    
                        this.logger.LogDebug(string.Format(CultureInfo.InvariantCulture, "Faulted Task, and instance of ReportGeneratorThread is recreated and corresponding task is started"));
                        break;
                    }
                }
            }
            else
            {
                this.logger.LogEvent(this.Id.ToString(), string.Format(CultureInfo.InvariantCulture, "System"), string.Format(CultureInfo.InvariantCulture, "Task " + taskException.Task.Id + " has thrown a Task Canceled Exception"));
                // Cancelling tasks...time to exit
                return;
            }
        }
    }    
}

以上将循环，在出现错误的任务时立即重新启动，但如果其中一个被取消，则完全退出。

注意:缺少一个好的代码示例来开始，上面是浏览器代码:完全未编译，未测试。我想不起WhenAll()和WhenAny()如何传播异常的具体细节;我想我的例子是正确的，但是完全有可能您需要调整细节以使其工作。

相关文章：