Remote actor timeout cancellation

[netclectic]

Is there any way for a remote actor, receiving a message with Ask, to know the timeout that was set?

For instance, if an actor is fetching data from a 3rd party api that accepts a cancellation token, is it possible for the actor to trigger the cancellation on timeout? It seems that only the calling actor knows about the timeout exception.

[Aaronontheweb]

@netclectic to do this, you would need to incorporate the request time into the content of the message itself.

In some of my applications and our client's applications I will often include a simple readonly struct Deadline that looks like this:

// Deadline struct in C# computed from the current time and the timeout
// value. The deadline is used to determine if a request has timed out.
public readonly struct Deadline
{
    public Deadline(TimeSpan timeout)
    {
        Timeout = timeout;
        DeadlineTime = DateTime.UtcNow + timeout;
    }

    public TimeSpan Timeout { get; }
    public DateTime DeadlineTime { get; }

    public bool IsOverdue => DeadlineTime < DateTime.UtcNow;
}

I include that in the properties of my message and then check to see if the message is overdue - if it is, I don't bother fully processing it. I have a sample that does this here: https://github.com/Aaronontheweb/AkkaStreams.Demo.HttpClient/blob/2c9dcb0394839cfe4c8541c60dc9ef8e3b66ca3a/StreamStages/RequestsWithDeadline.cs

Does that help @netclectic ?

[netclectic]

Yes, thanks.

I realised I can just pass the timeout in the message and create a new CancellationTokenSource at the remote side, passing the timeout into the constructor.