等待任务.当所有(任务)异常处理时,记录任务中的所有异常
本文关键字:任务 记录 异常 等待 异常处理 | 更新日期: 2024-09-23 19:53:36
我正试图从下面的代码中找出如何报告任务列表引发的所有异常。
这个代码片段的基本思想是:用户向处理程序发送一个请求,处理程序创建消息tasks
并将它们发送到一个类,该类将它们发送给外部系统。我包括了以下涉及的方法。
我必须关闭一些东西,因为我正在调试异常处理程序,而任务exception总是为null,因为除非我在断点中停留足够长的时间,否则它们的状态似乎是Waiting for Activiation
。
// Handle the user request
public async void Handle(WriteScanToSys settings)
{
_successfulScanIds = new List<int>();
// create the messages as tasks
var tasks = _factory.CreateMessage(settings).Select(msg => SendScans(msg));
try
{
// wait for all of them to complete
await Task.WhenAll(tasks); // I had ConfigureAwait(false) here, but took it off
}
catch (Exception)
{
foreach (var task in tasks.Where(t => t.Exception != null))
{
// ELMAH
var errorLog = ErrorLog.GetDefault(null);
errorLog.Log(new Error(task.Exception));
}
}
// save to repository
}
// the task to perform
private async Task<IDictionary<string, object>> SendScans(IDictionary<string, object> data)
{
object sysMsg = null;
var response = await _msgCenter.SendMessage(data);
response.TryGetValue("SystemMessage", out sysMsg);
_successfulScanIds.Add(Convert.ToInt32(data["Id"]));
return response;
}
// the communication with the external system (The message center class)
private async Task<IDictionary<string, object>> SendMessage(IDictionary<string, object> msg)
{
var response = new Dictionary<string, object>();
var response = await _client.sendAsync(
new BodyOfRequest(
// Compose Object
));
if (response.ScreenMessage != "SUCCESSFUL")
throw new CustomException("The transaction for job " + job + " failed with msg: " + body.ScreenMessage);
response.Add("SystemMessage", body.ScreenMessage);
return response;
}
您违反了懒惰评估-每次迭代Select
的结果都会创建一组新的任务。只需调用ToList()
:即可解决此问题
var tasks = _factory.CreateMessage(settings)
.Select(msg => SendScans(msg))
.ToList();
这样,您正在等待的任务集将与foreach
循环检查的任务集相同。
您可以从Task.WhenAll
-Task:中获得异常(如果有的话),而不是迭代所有任务
var taskResult = Task.WhenAll(tasks);
try
{
await taskResult;
}
catch (Exception e)
{
if (taskResult.IsCanceled)
{
// Cancellation is most likely due to a shared cancellation token. Handle as needed, possibly check if ((TaskCanceledException)e).CancellationToken == token etc.
}
else if (taskResult.IsFaulted)
{
// use taskResult.Exception which is an AggregateException - which you can iterate over (it's a tree! .Flatten() might help)
// caught exception is only the first observed exception
}
else
{
// Well, this should not really happen because it would mean: Exception thrown, not faulted nor cancelled but completed
}
}