Akka演员：需要一个例子来了解一些基础知识 [英] Akka Actors: Need an example to understand some basics

问题描述

我正在修补Akka，并需要一些建议如何实现我想到的具体。我想有一个演员，我可以发送 DownloadFile（URI，文件）消息，并下载它。由于这可以并行，我不想下载文件后文件，但有并发下载的限制。

I'm tinkering with Akka and need some advice how to implement something specific i have in mind. I want to have an actor which i can send a DownloadFile(URI, File) message and downloads it. Since this can be paralleled, I don't want to download file after file but have a limit of concurrent downloads.

使用Akka建模的方法是什么？其他的事情，想到的是：如果一个工人的演员因某种原因死亡会发生什么？如何重试下载？等等。

Whats the intended way to model something like this with Akka? Other things that come to mind are: What happens if one of the "worker" actor dies for some reason? How to retry the download? Etc. etc.

我知道这是一个非常巨大的问题，但我希望有人花时间回答它！谢谢！

I know this is a very huge question but i hope someone takes the time to answer it! Thank you!

推荐答案

它会创建三个 - 但你可以配置它来创建尽可能多的你喜欢 - 下载器，以便三个下载请求可以并发处理。

Give this a shot; it creates three - but you could configure it to create as many as you like - downloaders, so that three download requests could be processed concurrenty.

sealed trait DownloaderMessage
case class DownloadFile(uri: URI, file: File) extends DownloaderMessage

object Downloader {
  val dispatcher = Dispatchers.newExecutorBasedEventDrivenWorkStealingDispatcher("pool").build
}

class Downloader extends Actor {
  self.lifeCycle = Permanent
  self.dispatcher = Downloader.dispatcher
  def receive = {
    case DownloadFile(uri, file) =>
      // do the download
  }
}

trait CyclicLoadBalancing extends LoadBalancer { this: Actor =>
  val downloaders: List[ActorRef]
  val seq = new CyclicIterator[ActorRef](downloaders)
}

trait DownloadManager extends Actor {
  self.lifeCycle = Permanent
  self.faultHandler = OneForOneStrategy(List(classOf[Exception]), 5, 5000)
  val downloaders: List[ActorRef]
  override def preStart = downloaders foreach { self.startLink(_) }
  override def postStop = self.shutdownLinkedActors()
}

class DownloadService extends DownloadManager with CyclicLoadBalancing {
  val downloaders = List.fill(3)(Actor.actorOf[Downloader])
}

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