Understanding tuning akka dispatchers (by Jami allan)

[AL]

Reading tuning akka dispatchers article by Jami allan. he writes:

If you suspect you will need to use a Router somewhere, Akka Team Lead Roland Kuhn recommends that you pass around actor references from supervisors to compute-intensive children so that the ‘context.parent’ of their children are free to become a router later on with minimal impact. But do not create Routers before you have proven at runtime under load that you absolutely need to.

can anyone elaborate on that with a simple example ? 

Thanks in advance

[Rob Crawford]

With the Java API, something like this:

public class ComputeIntensiveChild extends AbstactActor {

private final ActorRef realParent;

public static Props create(ActorRef realParent) {

    return Props.create(ComputeIntensiveChild.class, realParent);

}

public ComputeIntensiveChild(ActorRef realParent) {

    this.realParent = realParent;

}

public Receive createReceive() {

...

}

}

This way you send the answer to realParent instead of getContext().getParent(). Even if there's a router between the child and realParent, the intended recipient gets the message.

BUT I'm not sure this isn't a premature optimization. Since there's a possibility of a router in the mix, that means the child is sending a response to a message it received. In that case, just 

send the response to the sender -- routers always forward messages, preserving the original sender. 

[AL]

Thanks,
The scala API is different. but I am not sure that this is what he meant

[Rob Crawford]

What do you believe he meant?

[AL]

don't know really. I take my words back :)  what you wrote makes perfect sense. thanks

[Roland Kuhn]

Sorry for the long delay. Jamie’s advice combines two concerns, one has been explained by Rob, the other is that routers have historically been severely overused—they serve a very specific need that does not arise frequently.

Regards, Roland 

Sent from my iPhone

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