Exception handling Async.Catch对OperationCanceledException不起作用
我使用Async.Catch处理异步工作流引发的异常:Exception handling Async.Catch对OperationCanceledException不起作用,exception-handling,f#,async-workflow,Exception Handling,F#,Async Workflow,我使用Async.Catch处理异步工作流引发的异常: work |> Async.Catch |> Async.RunSynchronously |> fun x -> match x with | Choice1Of2 _ -> () // success | Choice2Of2 ex -> // failure, handle exception 今天我注意到OperationCanceledExcep
work
|> Async.Catch
|> Async.RunSynchronously
|> fun x -> match x with
| Choice1Of2 _ -> () // success
| Choice2Of2 ex -> // failure, handle exception
今天我注意到OperationCanceledException不是由Async.Catch处理的。而不是从Async.Catch获得选择,异常会不断冒泡,直到它击中我。我希望下面的测试是红色的,但它是绿色的:
[<Test>]
let ``Async.Catch doesnt work on OperationCancelledExceptions``() =
use cancellationTokenSource = new System.Threading.CancellationTokenSource(1000)
let work = async {
while true do
do! Async.Sleep 100
}
(fun () -> work
|> Async.Catch
|> fun x -> Async.RunSynchronously (x, cancellationToken=cancellationTokenSource.Token)
|> ignore)
|> should throw typeof<System.OperationCanceledException>
[]
让“`Async.Catch在OperationCancelledExceptions”上不起作用()=
使用cancellationTokenSource=new System.Threading.cancellationTokenSource(1000)
让工作=异步{
尽管如此
做!异步。睡眠100
}
(乐趣()->工作
|>异步捕获
|>fun x->Async.RunSynchronously(x,cancellationToken=cancellationTokenSource.Token)
|>忽略)
|>应该抛出类型
使用Async.Catch+Choices+matching评估某些异常,使用try/Catch块评估其他异常似乎不正确。。。它看起来像下面这样,太复杂了。除此之外,我想知道Async.Catch有什么用途,因为我必须使用try/Catch块…:
[<Test>]
let ``evaluating exceptions of async workflows``() =
use cancellationTokenSource = new System.Threading.CancellationTokenSource(1000)
let work = async {
while true do
do! Async.Sleep 100
}
try
work
|> Async.Catch
|> fun x -> Async.RunSynchronously (x, cancellationToken=cancellationTokenSource.Token)
|> fun x -> match x with
| Choice1Of2 result -> () // success, process result
| Choice2Of2 ex -> () // failure, handle exception
with ex -> () // another failure, handle exception here too
[]
让“`评估异步工作流的异常”`()=
使用cancellationTokenSource=new System.Threading.cancellationTokenSource(1000)
让工作=异步{
尽管如此
做!异步。睡眠100
}
尝试
工作
|>异步捕获
|>fun x->Async.RunSynchronously(x,cancellationToken=cancellationTokenSource.Token)
|>乐趣x->将x与
|Choice1Of2结果->()//成功,处理结果
|Choice2Of2 ex->()//失败,处理异常
使用ex->()//另一个失败,在这里也处理异常
处理异步工作流异常的最佳方法是什么?我应该转储Async.Catch并在任何地方使用try/Catch块吗?取消是异步计算中的一种特殊异常。取消工作流时,也会取消所有子计算(共享取消令牌)。所以,如果你可以把取消作为一个普通的异常处理,它仍然可以取消你计算的其他部分(这将很难解释到底发生了什么) 但是,您可以编写一个原语来启动工作流(并将其与父工作流分离),然后在此子工作流中处理取消
type Async =
static member StartCatchCancellation(work, ?cancellationToken) =
Async.FromContinuations(fun (cont, econt, _) ->
// When the child is cancelled, report OperationCancelled
// as an ordinary exception to "error continuation" rather
// than using "cancellation continuation"
let ccont e = econt e
// Start the workflow using a provided cancellation token
Async.StartWithContinuations( work, cont, econt, ccont,
?cancellationToken=cancellationToken) )
用法类似于Async.Catch
,但您必须将取消令牌传递给startcachcancellation
,而不是将其传递给同步运行的主(因为工作流是单独启动的):
谢谢你的解释,有道理。您还回答了我的另一个问题:“当工作流被取消时,这也会取消所有子计算”。我想问这个问题,因为MSDN文档没有告诉当其父计算被取消时,子计算会发生什么。
let work =
async { while true do
do! Async.Sleep 100 }
let ct = new System.Threading.CancellationTokenSource(10000)
Async.StartCatchCancellation(work, ct.Token)
|> Async.Catch
|> Async.RunSynchronously
|> printfn "%A"