Question

我正在研究Akka EventBus以检查它是否可以解决我的一个设计问题而且我仍然不知道。问题如下。

简化，我有：

case class Request(requesterId: String, operation: String, header:  RequestHeader)
case class Response(requesterId: String, operation: String, header: ResponseHeader)

我有几个具有不同功能的演员，我希望某个演员根据Response订阅requesterId，其他一些则取决于operation。有没有办法通过EventBus和分类器轻松实现这一目标？

谢谢，乔尔

Answer 1

当然，它被称为LookupEventBus。您可以通过扩展它来实现自己的总线，并在requesterId方法中提取classify，如下所示：

class LookupBusImpl extends EventBus with LookupClassification {
  type Event = HasRequesterId // I made up a super type for you here
  type Classifier = String
  type Subscriber = ActorRef

  override def classify(event: HasRequesterId): String = event.requesterId

然后您订阅了给定的requesterId，如下所示：

  lookupBus.subscribe(actorRef, "requester-100")

然后，此Actor将只收到已被归类为requester-100的消息。

Answer 2

我同意Konrad的意见，您应该实施新的LookupClassification公交车来解决您的问题。我认为最简单的是有两个单独的这些总线实例，一个按requestterId分类，另一个按操作分类。这种方法的一些基本设置工作是：

//Singleton to hold the instances of each stream type
object ResponseEventStream{
  val RequestorIdStream = new RequestorIdResponseEventStream
  val OperationStream = new OperationResponseEventStream
}

//Common functionality for the two different types of streams
trait ResponseEventStream extends ActorEventBus with LookupClassification{
  import ResponseEventStream._
  type Event = Response
  type Classifier = String  
  protected def mapSize = 128
  protected def publish(resp:Response, subscriber: ActorRef) = {
    if (subscriber.isTerminated) unsubscribe(subscriber)
    else subscriber ! resp
  }  
}

//Concrete impl that uses requesterId to classify
class RequestorIdResponseEventStream extends ResponseEventStream{
  protected def classify(resp:Response) = resp.requesterId 
}

//Concrete impl that uses operation to classify
class OperationResponseEventStream extends ResponseEventStream{
  protected def classify(resp:Response) = resp.operation 
}

//Trait to mix into classes that need to publish or subscribe to response events
//Has helper methods to simplify interaction with the two distinct streams
trait ResponseEventing{
  import ResponseEventStream._

  def publishResponse(resp:Response){
    RequestorIdStream.publish(resp)
    OperationStream.publish(resp)
  }

  def subscribeByRequestId(requestId:String, ref:ActorRef){
    RequestorIdStream.subscribe(ref, requestId)
  }

  def subscribeByOperartion(op:String, ref:ActorRef){
    OperationStream.subscribe(ref, op)
  }  
}

然后你只需要将ResponseEventing特征混合到需要发布Response事件或需要订阅它们的actor的actor中。正在发布的演员将调用publishResponse，需要订阅的演员将调用subscribeXXX，具体取决于他们感兴趣的分类（requesterId或操作）。

Akka scala事件总线具有不同的分类器，具体取决于订户

2 个答案: