Akka中的Actor询问超时-持久性

Question

我尝试了一个带有MongoDb支持的akka-persistence的“Hello-World”示例，使用这个开源https://github.com/scullxbones/akka-persistence-mongo/tree/master/rxmongo/src。下面是我的代码。但是，当我运行应用程序时，我得到了ask Timeout：

Akka.Pattern.AskTimeoutException：[Akka://Example/User/SampleActor#1876558089]]在[2000毫秒]之后询问超时。发件人[null]发送了类型为“actors.command”的消息。

import akka.actor.{ActorSystem, Props}
import akka.pattern.ask
import akka.persistence.{PersistentActor, RecoveryCompleted}
import akka.util.Timeout

import scala.concurrent.Await
import scala.concurrent.duration._
import scala.language.postfixOps

object Main extends App {
  implicit val timeout = Timeout(2 seconds)
  val system = ActorSystem("example")

  var actor = system.actorOf(SampleActor.props(), "sampleActor")
  Await.result(actor ? Command("first"), Duration.Inf)
  Await.result(actor ? Command("second"), Duration.Inf)

  system.stop(actor)
  system.terminate()
}

case class Command(value: String)

case class Event(value: String)

case class SampleState(counter: Int, lastValue: Option[String])

class SampleActor extends PersistentActor {
  override def persistenceId = "id-1"

  var state = SampleState(0, None)

  def updateState(event: Event): Unit = {
    state = state.copy(counter = state.counter + 1, lastValue = Some(event.value))
  }

  override val receiveCommand: Receive = {
    case Command(value) =>
      persist(Event(value))(updateState)
  }

  override def receiveRecover: Receive = {
    case event: Event =>
      updateState(event)
    case RecoveryCompleted =>
      println("Recovery completed")
  }
}

object SampleActor {
  def props(): Props = Props(new SampleActor())
}

下面是我的application.conf：

contrib {
    persistence {
      mongodb {
        mongo {
          mongouri = "mongodb://localhost:27017/akka-persistence"
          driver = "akka.contrib.persistence.mongodb.RxMongoPersistenceExtension"
        }
        rxmongo {
          failover {
            initialDelay = 750ms
            retries = 10
            growth = con
            factor = 1.5
          }
        }
      }
    }

  }

如果我使用tell（！）而不是ask（？），什么都没有发生，数据库没有创建，也没有命令持久化。

谢谢！

Answer 1

在application.conf中，您应该分配日志和快照插件：

akka.persistence.journal.plugin = "akka-contrib-mongodb-persistence-journal"
akka.persistence.snapshot-store.plugin = "akka-contrib-mongodb-persistence-snapshot"

并且您应该回复发件人,因此receive变为：

override val receiveCommand: Receive = {
   case Command(value) =>
     persist(Event(value)) { persistedEvent =>
        updateState(persistedEvent)
        sender ! SomeResponse
     }
}