Question

我正在玩Akka Streams并且一直在尝试对从MongoDB集合中调查的事件进行一些丰富和处理。但是，我对实现我的事件丰富程序的最佳方法有些怀疑，这可能需要连接到外部数据源。

mapFuture似乎很合适，但我遇到了一些问题：

class EventEnricherActor extends Actor with ActorLogging {

  // ...

  def receive = {
    case e: Event =>
      sender ! augmentEvent(e)
  }

}

我的应用：

val enricherActor = actorSystem.actorOf(Props[EventEnricherActor])

Flow(mongodbConsumer).
      mapFuture(msg => enricherActor ? msg).
      onComplete(materializer) { _ => actorSystem.shutdown()}

但是，我坚持这个错误：

java.lang.ClassCastException: messages.Event cannot be cast to scala.runtime.Nothing$

对mapFuture的调用。

我错过了什么？

处理这些丰富的任何更好的想法？

更新堆栈跟踪：

[ERROR] [08/12/2014 11:48:07.314] [actor-system-akka.actor.default-dispatcher-2] [akka://actor-system/user/flow-1-2-transform] failure during processing
java.lang.ClassCastException: messages.Event cannot be cast to scala.runtime.Nothing$
    at apps.Consume$$anonfun$1$$anonfun$apply$1.apply(Consume.scala:47)
    at akka.stream.impl.MapFutureProcessorImpl$$anonfun$1.apply$mcV$sp(MapFutureProcessorImpl.scala:125)
    at akka.stream.impl.Pump$$anonfun$pump$1.apply$mcV$sp(Transfer.scala:163)
    at akka.stream.impl.Pump$$anonfun$pump$1.apply(Transfer.scala:163)
    at akka.stream.impl.Pump$$anonfun$pump$1.apply(Transfer.scala:163)
    at akka.stream.impl.ActorBasedFlowMaterializer$.withCtx(ActorBasedFlowMaterializer.scala:133)
    at akka.stream.impl.Pump$class.pump(Transfer.scala:163)
    at akka.stream.impl.ActorProcessorImpl.pump(ActorProcessor.scala:238)
    at akka.stream.impl.BatchingInputBuffer.enqueueInputElement(ActorProcessor.scala:93)
    at akka.stream.impl.BatchingInputBuffer$$anonfun$upstreamRunning$1.applyOrElse(ActorProcessor.scala:140)
    at scala.runtime.AbstractPartialFunction$mcVL$sp.apply$mcVL$sp(AbstractPartialFunction.scala:33)
    at scala.runtime.AbstractPartialFunction$mcVL$sp.apply(AbstractPartialFunction.scala:33)
    at scala.runtime.AbstractPartialFunction$mcVL$sp.apply(AbstractPartialFunction.scala:25)
    at akka.stream.impl.SubReceive.apply(Transfer.scala:18)
    at akka.stream.impl.SubReceive.apply(Transfer.scala:14)
    at scala.PartialFunction$class.applyOrElse(PartialFunction.scala:118)
    at akka.stream.impl.SubReceive.applyOrElse(Transfer.scala:14)
    at scala.PartialFunction$OrElse.applyOrElse(PartialFunction.scala:165)
    at scala.PartialFunction$OrElse.applyOrElse(PartialFunction.scala:166)
    at akka.actor.Actor$class.aroundReceive(Actor.scala:465)
    at akka.stream.impl.ActorProcessorImpl.aroundReceive(ActorProcessor.scala:238)
    at akka.actor.ActorCell.receiveMessage(ActorCell.scala:516)
    at akka.actor.ActorCell.invoke(ActorCell.scala:487)
    at akka.dispatch.Mailbox.processMailbox(Mailbox.scala:238)
    at akka.dispatch.Mailbox.run(Mailbox.scala:220)
    at akka.dispatch.ForkJoinExecutorConfigurator$AkkaForkJoinTask.exec(AbstractDispatcher.scala:393)
    at scala.concurrent.forkjoin.ForkJoinTask.doExec(ForkJoinTask.java:260)
    at scala.concurrent.forkjoin.ForkJoinPool$WorkQueue.runTask(ForkJoinPool.java:1339)
    at scala.concurrent.forkjoin.ForkJoinPool.runWorker(ForkJoinPool.java:1979)
    at scala.concurrent.forkjoin.ForkJoinWorkerThread.run(ForkJoinWorkerThread.java:107)

由于

Answer 1

我的错误，mongodbConsumer（一个ActorProducer）是无类型的！

所以这个：

val mongodbConsumer = ActorProducer[Event](system.actorOf(MongodbConsumerActor.props(db)))

而不是：

val mongodbConsumer = ActorProducer(system.actorOf(MongodbConsumerActor.props(db)))

在akka流中使用mapFuture

1 个答案: