Programmatically obtain ephemeral port with Akka

Question

If I configure an ActorSystem in Akka to use an emphemeral tcp port (more specifically, I configure the http port to 0), is there a way to programmatically obtain this port once the ActorSystem is started?

Any attempts to create an actor using actorOf, and then printing out the actor path shows a locally-referenced actor. Additionally, I tried registering a RemoteLifeCycleEvent listener on the event stream, but this can only be done after the server has been started, and hence misses RemoteServerStarted event.

score 3 · Accepted Answer · answered Feb 21 '13 at 18:37

Here you go:

class MyExtensionImpl(system: ExtendedActorSystem) extends Extension {
  def address = system.provider match {
    case rarp: RemoteActorRefProvider => rarp.transport.address
    case _ => system.provider.rootPath.address
  }
}

object MyExtension extends ExtensionKey[MyExtensionImpl]

val address = MyExtension(system).address
val port = address.port.getOrElse(sys.error("not a remote actor system"))

(note this code works with Akka 2.0.x. In 2.1.x you can avoid going through RemoteActorRefProvider by using system.provider.getDefaultAddress)

Programmatically obtain ephemeral port with Akka

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