Using Futures

futures.scala

// This is not a particularly impressive example of using futures.
def getMetrics: List[EgraphsMetric[Int]] = {

  import akka.pattern.{ ask, pipe }

  val futureMetrics: List[Future[EgraphsMetric[Int]]] = for (actor <- actors: List[ActorRef]) yield {
    implicit val timeout = Timeout(5 seconds)

    for {
      metric <- ask(actor, GetMetric).mapTo[EgraphsMetric[Int]]
    } yield metric    
  }

  for (futureMetric <- futureMetrics) yield Await.result(futureMetric, 10.seconds)
}

List[Future[EgraphsMetric[Int]]]

val futureMetrics: Future[List[EgraphsMetric[Int]]]

val futureValues: Future[List[JsValue]] = for (
  metrics:List[EgraphMetric] <- futureMetrics;
  metric:EgraphMetric[Int] <- metrics
) yield {
  metric.toJson
}

val futureJsArray: Future[Json] = for(jsValuesList <- futureValues) yield Json.toJson(jsValuesList.toSeq)
val jsArray:JsArray = Await.result(futureJsArray, 5.seconds)

Ok(jsArray)