scala - Akka Actor : Remote actor exception "Futures timed out after"

Question

我是 Akka 新手，我使用 Akka 2.3.3 版本来创建 actor。我将创建远程参与者并尝试使用客户端进行访问。每当我要运行测试用例时，都会抛出以下异常:

[INFO] [04/27/2016 07:51:23.727] [Localsystem-akka.actor.default-dispatcher-3] [akka://Localsystem/deadLetters] Message [com.harmeetsingh13.chapter2.messages.SetRequest] from Actor[akka://Localsystem/temp/$a] to Actor[akka://Localsystem/deadLetters] was not delivered. [1] dead letters encountered. This logging can be turned off or adjusted with configuration settings 'akka.log-dead-letters' and 'akka.log-dead-letters-during-shutdown'.
[INFO] [04/27/2016 07:51:23.745] [Localsystem-akka.actor.default-dispatcher-3] [akka://Localsystem/deadLetters] Message [com.harmeetsingh13.chapter2.messages.GetRequest] from Actor[akka://Localsystem/temp/$b] to Actor[akka://Localsystem/deadLetters] was not delivered. [2] dead letters encountered. This logging can be turned off or adjusted with configuration settings 'akka.log-dead-letters' and 'akka.log-dead-letters-during-shutdown'.

Futures timed out after [10 seconds]
java.util.concurrent.TimeoutException: Futures timed out after [10 seconds]
at scala.concurrent.impl.Promise$DefaultPromise.ready(Promise.scala:219)
at scala.concurrent.impl.Promise$DefaultPromise.result(Promise.scala:223)
at scala.concurrent.Await$$anonfun$result$1.apply(package.scala:190)
at scala.concurrent.BlockContext$DefaultBlockContext$.blockOn(BlockContext.scala:53)
at scala.concurrent.Await$.result(package.scala:190)
at com.harmeetsingh13.chapter2.SClientIntegrationSpec$$anonfun$1$$anonfun$apply$mcV$sp$1.apply$mcV$sp(SClientIntegrationSpec.scala:18)
at com.harmeetsingh13.chapter2.SClientIntegrationSpec$$anonfun$1$$anonfun$apply$mcV$sp$1.apply(SClientIntegrationSpec.scala:15)
at com.harmeetsingh13.chapter2.SClientIntegrationSpec$$anonfun$1$$anonfun$apply$mcV$sp$1.apply(SClientIntegrationSpec.scala:15)
at org.scalatest.Transformer$$anonfun$apply$1.apply$mcV$sp(Transformer.scala:22)
at org.scalatest.OutcomeOf$class.outcomeOf(OutcomeOf.scala:85)
at org.scalatest.OutcomeOf$.outcomeOf(OutcomeOf.scala:104)
at org.scalatest.Transformer.apply(Transformer.scala:22)
at org.scalatest.Transformer.apply(Transformer.scala:20)
at org.scalatest.FunSpecLike$$anon$1.apply(FunSpecLike.scala:422)
at org.scalatest.Suite$class.withFixture(Suite.scala:1122)
at com.harmeetsingh13.chapter2.SClientIntegrationSpec.withFixture(SClientIntegrationSpec.scala:11)
at org.scalatest.FunSpecLike$class.invokeWithFixture$1(FunSpecLike.scala:419)
at org.scalatest.FunSpecLike$$anonfun$runTest$1.apply(FunSpecLike.scala:431)
at org.scalatest.FunSpecLike$$anonfun$runTest$1.apply(FunSpecLike.scala:431)
at org.scalatest.SuperEngine.runTestImpl(Engine.scala:306)
at org.scalatest.FunSpecLike$class.runTest(FunSpecLike.scala:431)
at com.harmeetsingh13.chapter2.SClientIntegrationSpec.runTest(SClientIntegrationSpec.scala:11)
at org.scalatest.FunSpecLike$$anonfun$runTests$1.apply(FunSpecLike.scala:464)
at org.scalatest.FunSpecLike$$anonfun$runTests$1.apply(FunSpecLike.scala:464)
at org.scalatest.SuperEngine$$anonfun$traverseSubNodes$1$1.apply(Engine.scala:413)
at org.scalatest.SuperEngine$$anonfun$traverseSubNodes$1$1.apply(Engine.scala:401)
............

我的服务器代码如下:Main.scala

object Main extends App{


 private val configFile = getClass.getClassLoader.getResource("application.conf").getFile;
 private val config = ConfigFactory.parseFile(new File(configFile ))

 val system = ActorSystem("SimpleClientServer", config)
 system.actorOf(Props[AkkadmeyDB], name = "akkademy-db")
}

应用程序.conf:

akka{
 actor{
  provider = "akka.remote.RemoteActorRefProvider"
 }
remote{
 enabled-transports = ["akka.remote.netty.tcp"]
  netty.tcp {
   hostname = "127.0.0.1"
   port = 2552
  }
  log-sent-messages = on
  log-received-messages = on
 }
}

AkkadmeyDB.scala Actor 类:

class AkkadmeyDB extends Actor{

 val map = new HashMap[String, Object]
 val log = Logging(context.system, this)

 override def receive: Receive = {
  case SetRequest(key, value) =>
   log.info("received SetRequest - key: {} value: {}", key, value)
   map.put(key, value)
   sender() ! Status.Success
  case GetRequest(key) =>
   log.info("received GetRequest - key: {}", key)
   val response = map.get(key)
   response match{
     case Some(x) => sender() ! x
     case None => Status.Failure(new KeyNotFoundException(key))
   }
   case o => Status.Failure(new ClassNotFoundException())
  }
 }

客户端代码如下:SClient.scala

class SClient(remoteIp: String) {

  private implicit val timeout = Timeout(10 seconds)
  private implicit val system = ActorSystem("Localsystem")
  private val remoteAddress = s"akka.tcp://SimpleClientServer@$remoteIp/user/akkademy-db";
  private val remoteDb = system.actorSelection(remoteAddress)

  def set(key: String, value: Object) = {
   remoteDb ? SetRequest(key, value)
  }

  def get(key: String) = {
    remoteDb ? GetRequest(key)
  }
}

SClientIntegrationSpec.scala 测试用例:

class SClientIntegrationSpec extends FunSpecLike with Matchers {

  val client = new SClient("127.0.0.1:2552")
  describe("akkadment-db-client"){
    it("should set a value"){
      client.set("jame", new Integer(1313))
      val futureResult = client.get("james")
      val result = Await.result(futureResult, 10 seconds)
      result should equal (1313)
    }
  }
}

当我看到远程应用程序的日志时，似乎请求命中没有发送到服务器。我的示例代码运行有什么问题？

Answer 1

为了解决上述问题，我们需要遵循以下两个步骤:

1. 当我创建服务器代码时，我从服务器应用程序中排除 application.conf，这就是客户端应用程序无法与服务器连接的原因。 built.sbt中使用的代码如下:

   mappings in (Compile, packageBin) ~= { _.filterNot { case (_, name) =>
    Seq("application.conf").contains(name)
   }}
   

注释掉上面的代码后，客户端成功看到服务端。

在学习Scala 第2章 jasongoodwin中解释了客户端和服务器Actor系统的代码。但书中有一些勘误表，并且缺少客户端的 application.conf 配置。因为当我们在同一台 PC 上运行这两个代码时，我们已经面临端口绑定(bind)异常，因为默认情况下参与者使用 2552 端口进行访问，并且我们已经为我们的服务器应用程序定义了该端口。因此，application.conf 还需要客户端，如下所示:

akka {
  actor {
    provider = "akka.remote.RemoteActorRefProvider"
  }
  remote {
    enabled-transports = ["akka.remote.netty.tcp"]
    netty.tcp {
      hostname = "127.0.0.1"
      port = 0
    }
    log-sent-messages = on
    log-received-messages = on
  }
}

这里端口0表示任何空闲端口。

之后，上面的代码就成功运行了。