Shutting down Akka actor if AskTimeout reached

Short answer is no, you cannot do it.

Long answer is it depends.

You could move actor's work to another execution context via a Future for example. This will allow your actor react on other messages but that Future that actor has started cannot be cancelled if it was picked up by an execution context and not hanging in the queue of the execution context.

You could write some smart Future wrapper that would check if future was cancelled before starting the work. But if processing has started, the only thing you can do is calling interrupt on the thread executing the future (meaning that you need to capture this thread somehow) and hopping that the work will hit Object.wait or Thread.sleep methods, ie the only places when the interrupt exception can be received. But there is no guarantee of this ever happening.

No you can't. The only thing you can do to an actor is send a message to it. You can't 'get' the actor in any kind of other kind of way to interrupt it. And since, under normal circumstances, messages are processed in order any subsequent "stop processing" message will only be processed after the first message was already completed.

I think the solution to your problem will depend a bit on why you suspect the actor may "time out" in responding.

For example, where you might expect the Actor may sometimes have a backlog of messages, I think the best solution may be to include the timeout as part of the message. In your receiveMessage handler you can check this "request expiry" time before doing actual work, and if the timeout has already passed, just discard the message.