Code for 2.2 spotlight: Cluster Member Age

MemberAge.scala

  // sort by age, oldest first
  val ageOrdering = Ordering.fromLessThan[Member] { (a, b) => 
    a.isOlderThan(b) 
  }
  var membersByAge: SortedSet[Member] = SortedSet.empty(ageOrdering)

  def receive = {
    case state: CurrentClusterState =>
      membersByAge = SortedSet.empty(ageOrdering) ++ state.members
    }
    case MemberUp(m)         ⇒ membersByAge += m
    case MemberRemoved(m, _) ⇒ membersByAge -= m
    case msg =>
      membersByAge.take(3).foreach { m ⇒
        val service = context.actorSelection(
          RootActorPath(m.address) / "user" / "service")
        service ! msg
      }
  }