I currently have code which dispatches a request using the Ask Pattern. The dispatched request will generate an Akka Actor which sends a HTTP request and then returns the response. I'm using Akka's circuit breaker API to manage issues with the upstream web services i call.
If the circuitbreaker is in an open state then all subsequent requests are failing fast which is the desired effect. However when the actor fails fast it just throws a CircuitBreakerOpenException, stops the actor however control does not return to the code which made the initial request until an AskTimeoutException is generated.
This is the code which dispatches the request
Timeout timeout = new Timeout(Duration.create(10, SECONDS));
Future<Object> future = Patterns.ask(myActor, argMessage, timeout);
Response res = (Response ) Await.result(future, timeout.duration());
This is the circuitbreaker
getSender().tell(breaker.callWithSyncCircuitBreaker(new Callable<Obj>()
{
@Override
public Obj call() throws Exception {
return fetch(message);
}
}), getSelf()
);
getContext().stop(getSelf());
When this block of code is executed and if the circuit is open it fails fast throwing an exception however i want to return control back to the code which handles the future without having to wait for a timeout.
Is this possible?
When an actor fails out and is restarted, if it was processing a message, no response will be automatically sent to that sender. If you want to send that sender a message on that particular failure then catch that exception explicitly and respond back to that sender with a failed result, making sure to capture the sender first before you go into any future callbacks to avoid closing over this mutable state. You could also try to do this in the preRestart, but that's not very safe as by that time the sender might have changed if you are using futures inside the actor.