具有Akka类型角色和群集分片的优先级邮箱

Question

我有一个带有类型化参与者的集群分片应用程序。演员看起来像这样：

object TestActor {

  sealed trait Command
  final case class Inte(i: Int) extends Command
  final case class Stringaki(s: String) extends Command

  val TypeKey = EntityTypeKey[Command]("Test")

  def defaultThreadBehavior(id: String): Behavior[Command] = Behaviors.setup { ctx =>

    Behaviors.receiveMessage { cmd =>
      cmd match {
        case Inte(i) =>
          ctx.log.info(System.currentTimeMillis()/1000 + " Received int: " + i)
          Thread.sleep(1000)
        case Stringaki(s) =>
          ctx.log.info(System.currentTimeMillis()/1000 + " Received string: " + s)
          Thread.sleep(1000)
      }
      Behaviors.same
    }
  }

}

演员是通过分片信封创建的，如下所示：

val system_config = ConfigFactory.parseString(
      """
        |akka {
        |  actor {
        |    provider = "cluster"
        |    prio-dispatcher {
        |      type = "Dispatcher"
        |      mailbox-type = "PriorityMailbox"
        |    }
        |  }
        |  remote {
        |    netty.tcp {
        |      hostname = "127.0.0.1"
        |      port = 2551
        |    }
        |  }
        |  cluster {
        |    seed-nodes = [
        |      "akka.tcp://[email protected]:2551"
        |    ]
        |    sharding {
        |      number-of-shards = 10
        |      use-dispatcher = "akka.actor.prio-dispatcher"
        |    }
        |  }
        |}
        |""".stripMargin)

    val system = ActorSystem(Behaviors.empty[TestActor.Command], "TestApp",system_config)
    val sharding = ClusterSharding(system)

    val shardRegion = sharding.init(Entity(TestActor.TypeKey, ctx => defaultThreadBehavior(ctx.entityId)))

    (0 to 9).foreach{
      i =>
        shardRegion ! ShardingEnvelope(0.toString, Inte(i))
    }

    (0 to 9).foreach{
      i =>
        shardRegion ! ShardingEnvelope(0.toString, Stringaki(i.toString))
    }

两个for循环将消息发送到同一actor。第一个循环发送整数，第二个循环发送字符串。当参与者处理消息时，它会休眠以在队列中建立消息并测试优先级。优先级邮箱是在系统配置中配置的，UnboundedPriorityMailbox实现如下：

class PriorityMailbox (settings: Settings, cfg: Config) extends UnboundedPriorityMailbox(

  PriorityGenerator {
    case Stringaki => 0
    case _ => 1
  }

)

Actor为什么按消息到达的顺序打印消息，而不考虑优先级生成器？

Answer 1

为什么您看不到优先邮箱的简短答案是您的TestActor不是使用优先邮箱，而是默认邮箱。仅Akka群集分片系统正在使用优先级邮箱。 Cluster sharding reference.conf的akka.cluster.sharding.use-dispatcher描述：

# The id of the dispatcher to use for ClusterSharding actors.
# If specified you need to define the settings of the actual dispatcher.
# This dispatcher for the entity actors is defined by the user provided
# Props, i.e. this dispatcher is not used for the entity actors.

的确，您发送的每条消息都会通过优先级邮箱，但是由于群集分片内部的参与者没有处于休眠状态，因此没有积压的情况发生（尽管在某些情况下，尤其是内核较少的情况下，积压的优先级可能会发光）。

要使实体参与者在具有优先级邮箱的调度程序中运行，您将具有类似的内容

val entityDispatcherProps = DispatcherSelector.fromConfig("akka.actor.prio-dispatcher")
val baseEntity = Entity(TestActor.TypeKey)(ctx => defaultThreadBehavior(ctx.entityId))
val shardRegion = sharding.init(baseEntity.withEntityProps(entityDispatcherProps))