在一定时间后取消 Task.WhenAll

Posted 2023-03-31

【中文标题】在一定时间后取消 Task.WhenAll

【英文标题】：Cancelling Task.WhenAll after a certain amount of time

【发布时间】：2021-08-05 07:06:42

【问题描述】：

我有一个异步操作，它将航空公司列表作为参数并返回一些数据，并且我有一个航空公司列表，我想为其获取数据。

但是，如果在预定义的时间后我无法获得所有这些航空公司的数据，我想停止等待并将其他内容返回给用户。

public async Task Run()

    var watch = System.Diagnostics.Stopwatch.StartNew();
    await RunAirline();
    watch.Stop();
    Console.WriteLine($"Total Execution Time: watch.ElapsedMilliseconds + Environment.NewLine");
    //return $"Total Execution Time: watch.ElapsedMilliseconds + Environment.NewLine";
    //Console.ReadLine();


private static async Task RunAirline()

    try
    
        List<string> AirlineList = GetAirLineCodes();
        List<Task<WebsiteDataModel.WebsiteDataModel>> taskList = new List<Task<WebsiteDataModel.WebsiteDataModel>>();
        foreach (string AirlineCode in AirlineList)
        
            taskList.Add(Task.Run(() => CallindividualAirline(AirlineCode)));

        
        var result = await Task.WhenAll(taskList);
        foreach (WebsiteDataModel.WebsiteDataModel model in result)
        
            Display(model);
        
    
    catch (Exception Ex)
    
        Console.WriteLine(Ex.Message.ToString());
    


private static List<string> GetAirLineCodes()

    return new List<string>() 
    
        "A",
        "B",
        "C"
    ;


private static void Display(WebsiteDataModel.WebsiteDataModel result)

    Console.WriteLine($"Website Content as result.DataContent , Website Name as :  result.WebsiteName Status as : result.Status , Content length as : result.WebsiteData.Length ----- Error as  : result.error.FaultException.ToString()." + Environment.NewLine);


private static WebsiteDataModel.WebsiteDataModel CallindividualAirline(string AirlineCode)

    WebsiteDataModel.WebsiteDataModel LobjWebsiteDataModel = new WebsiteDataModel.WebsiteDataModel();
    WebsiteDataModel.ErrorData LobjErrorData = new WebsiteDataModel.ErrorData();
    try
    
        switch (AirlineCode)
        
            // calling Airline API...........
            case "A":
                ClsAirOne LobjAirOne = new ClsAirOne();
                LobjWebsiteDataModel = LobjAirOne.GetAirDataData("https://book.xxxxx.com");
                return LobjWebsiteDataModel;
            case "B":
                ClsAirTwo LobjAirTwo = new ClsAirTwo();
                LobjWebsiteDataModel = LobjAirTwo.GetAirData("https://book.xxxxx.in");
                return LobjWebsiteDataModel;
            case "C":
                ClsAirThree LobjAirThree = new ClsAirThree();
                LobjWebsiteDataModel = LobjAirThree.GetAirData("https://xxxxx.in/");
                return LobjWebsiteDataModel;

            default:
                return LobjWebsiteDataModel;
        


    
    catch (Exception Ex)
    

        LobjWebsiteDataModel.Status = "0";
        LobjWebsiteDataModel.WebsiteData = "";
        LobjErrorData.FaultException = "ERR-01" + Ex.Message.ToString();
        LobjWebsiteDataModel.error = LobjErrorData;
        return LobjWebsiteDataModel;
    

【问题讨论】：

有帮助吗？ ***.com/questions/9846615/…

CancellationTokenSource

@feihoa..........这两个 sn-ps 的组合实现了我的输出........await 任务。 WhenAny(Task.WhenAll(tasks), Task.Delay(timeout));var completedResults = tasks .Where(t => t.Status == TaskStatus.RanToCompletion) .Select(t => t.Result) .ToList() ;

var 结果 = await Task.WhenAny(Task.WhenAll(taskList), Task.Delay(TimeSpan.FromSeconds(Convert.ToDouble(ConfigurationManager.AppSettings["TimeOutInSeconds"]))));这个sn-p是否取消所有在特定时间内没有完成的任务

【参考方案1】：

执行此操作的最佳方法是取消传递给Task.WhenAll 的每个操作。您可以创建一个带有超时的取消令牌源，然后将其 CancellationToken 传递给实际执行 I/O 的方法。

例如：

public async Task Run()

  ...
  using var cts = new CancellationTokenSource(TimeSpan.FromSeconds(10));
  await RunAirline(cts.Token);
  ...


private static async Task RunAirline(CancellationToken cancellationToken)

  ...
  foreach (string AirlineCode in AirlineList)
    taskList.Add(Task.Run(() => CallindividualAirline(AirlineCode, cancellationToken)));
  ...


private static WebsiteDataModel.WebsiteDataModel CallindividualAirline(string AirlineCode, CancellationToken cancellationToken)

  ...
  ClsAirOne LobjAirOne = new ClsAirOne();
  LobjWebsiteDataModel = LobjAirOne.GetAirDataData("https://book.xxxxx.com", cancellationToken);
  ...
  ClsAirTwo LobjAirTwo = new ClsAirTwo();
  LobjWebsiteDataModel = LobjAirTwo.GetAirData("https://book.xxxxx.in", cancellationToken);
  ...

【讨论】：

嗨斯蒂芬，我做了同样的事情。但它不会在 10 秒后停止。

@VIGNESHWARAN：您需要将 CancellationToken 一直传递给调用 API 的任何对象。