What is the point of AsyncTimeout action filter?

Question

Trying to decrease the timeout of a given operation of my controller (let's say it's Index) I annotated it with AsyncTimeout(5000).
Inside that method, the first line is await Task.Delay(10000).
I published that code to azure, guaranteeing that there's no debug="true" but even so, the request runs for 11-13 sec... so, in my opinion that is not how it's supposed to be used...

So, where should i use this attribute?

Details:
Using .net 4.7 (compilation and runtime) and latests asp.net mvc (5.2.3)

Answer 1

You should look to use the overload of Task.Delay that accepts the CancellationToken. The AsyncTimeout will trigger the cancellation in that case. Your code posted is not using a CancellationToken so I wouldn't expect anything different to happen without it.

UPDATE- Quick demo building on your question. This should throw a TaskCanceledException in about 5 seconds instead of waiting for the Task.Delay call of 15 seconds.

[AsyncTimeout(5000)]
public async Task<ActionResult> Index(CancellationToken cancellationToken)
{
    Stopwatch cancellationTimer = Stopwatch.StartNew();
    try
    {                
        await Task.Delay(15000, cancellationToken);
        cancellationTimer.Stop();
        return View();
    }
    catch (Exception e)
    {
         cancellationTimer.Stop();
         Debug.WriteLine($"Elapsed Time {cancellationTimer.ElapsedMilliseconds}");
         throw (e);
    }            
}