akka-typed(6) - cluster:group router, cluster-load-balancing

雪川大蟲發表於2020-06-11

先談談akka-typed的router actor。route 分pool router, group router兩類。我們先看看pool-router的使用示範:

      val pool = Routers.pool(poolSize = 4)(
        // make sure the workers are restarted if they fail
        Behaviors.supervise(WorkerRoutee()).onFailure[Exception](SupervisorStrategy.restart))
      val router = ctx.spawn(pool, "worker-pool")

      (0 to 10).foreach { n =>
        router ! WorkerRoutee.DoLog(s"msg $n")
      }

上面例子裡的pool是個pool-router,意思是一個有4個routees的routee池。每個routee都是通過WorkerRoutee()構建的,意味著routee池中只有一個種類的actor。pool-router是通過工廠方法直接在本地(JVM)構建(spawn)所有的routee。也就是說所有routee都是router的子actor。

再看看group-router的使用例子:

val serviceKey = ServiceKey[Worker.Command]("log-worker")

      // this would likely happen elsewhere - if we create it locally we
      // can just as well use a pool
      val workerRoutee = ctx.spawn(WorkerRoutee(), "worker-route")
      ctx.system.receptionist ! Receptionist.Register(serviceKey, workerRoutee)

      val group = Routers.group(serviceKey)
      val router = ctx.spawn(group, "worker-group")

      // the group router will stash messages until it sees the first listing of registered
      // services from the receptionist, so it is safe to send messages right away
      (0 to 10).foreach { n =>
        router ! WorkerRoutee.DoLog(s"msg $n")
      }

group-router與pool-router有較多分別:

1、routee是在router之外構建的,router是用一個key通過Receptionist獲取同key的actor清單作為routee group的

2、Receptionist是叢集全域性的。任何節點上的actor都可以傳送註冊訊息在Receptionist上登記

3、沒有size限制,任何actor一旦在Receptionist上登記即變成routee,接受router管理

應該說如果想把運算任務分配在叢集裡的各節點上並行運算實現load-balance效果,group-router是最合適的選擇。不過對不同的運算任務需要多少routee則需要使用者自行決定,不像以前akka-classic裡通過cluster-metrics根據節點負載情況自動增減routee例項那麼方便。

Receptionist: 既然說到,那麼就再深入一點介紹Receptionist的應用:上面提到,Receptionist是叢集全域性的。就是說任何節點上的actor都可以在Receptonist上註冊形成一個生存在叢集中不同節點的actor清單。如果Receptionist把這個清單提供給一個使用者,那麼這個使用者就可以把運算任務配置到各節點上,實現某種意義上的分散式運算模式。Receptionist的使用方式是:通過向本節點的Receptionist傳送訊息去登記ActorRef,然後通過Receptionist釋出的登記變化訊息即可獲取最新的ActorRef清單:

  val WorkerServiceKey = ServiceKey[Worker.TransformText]("Worker")

  ctx.system.receptionist ! Receptionist.Register(WorkerServiceKey, ctx.self)

  ctx.system.receptionist ! Receptionist.Subscribe(Worker.WorkerServiceKey, subscriptionAdapter)

Receptionist的登記和清單獲取是以ServiceKey作為關聯的。那麼獲取的清單內應該全部是一種型別的actor,只不過它們的地址可能是跨節點的,但它們只能進行同一種運算。從另一個角度說,一項任務是分佈在不同節點的actor並行進行運算的。

在上篇討論裡提過:如果釋出-訂閱機制是在兩個actor之間進行的,那麼這兩個actor也需要在規定的資訊交流協議框架下作業:我們必須注意訊息型別,提供必要的訊息型別轉換機制。下面是一個Receptionist登記示範:

object Worker {

  val WorkerServiceKey = ServiceKey[Worker.TransformText]("Worker")

  sealed trait Command
  final case class TransformText(text: String, replyTo: ActorRef[TextTransformed]) extends Command with CborSerializable
  final case class TextTransformed(text: String) extends CborSerializable

  def apply(): Behavior[Command] =
    Behaviors.setup { ctx =>
      // each worker registers themselves with the receptionist
      ctx.log.info("Registering myself with receptionist")
      ctx.system.receptionist ! Receptionist.Register(WorkerServiceKey, ctx.self)

      Behaviors.receiveMessage {
        case TransformText(text, replyTo) =>
          replyTo ! TextTransformed(text.toUpperCase)
          Behaviors.same
      }
    }
}

Receptionist登記比較直接:登記者不需要Receptionist返回訊息,所以隨便用ctx.self作為訊息的sender。注意TransformText的replyTo: ActorRef[TextTransformed],代表sender是個可以處理TextTransformed訊息型別的actor。實際上,在sender方是通過ctx.ask提供了TextTransformed的型別轉換。

Receptionist.Subscribe需要Receptionist返回一個actor清單,所以是個request/response模式。那麼傳送給Receptionist訊息中的replyTo必須是傳送者能處理的型別,如下:

  def apply(): Behavior[Event] = Behaviors.setup { ctx =>
    Behaviors.withTimers { timers =>
      // subscribe to available workers
      val subscriptionAdapter = ctx.messageAdapter[Receptionist.Listing] {
        case Worker.WorkerServiceKey.Listing(workers) =>
          WorkersUpdated(workers)
      }
      ctx.system.receptionist ! Receptionist.Subscribe(Worker.WorkerServiceKey, subscriptionAdapter)

...
    }
  

ctx.messageAdapter進行了一個從Receptionist.Listing返回型別到WorkersUpdated型別的轉換機制登記:從Receptionist回覆的List型別會被轉換成WorkersUpdated型別,如下:

...
   Behaviors.receiveMessage {
      case WorkersUpdated(newWorkers) =>
        ctx.log.info("List of services registered with the receptionist changed: {}", newWorkers)

...

另外,上面提過的TextTransformed轉換如下:

          ctx.ask[Worker.TransformText,Worker.TextTransformed](selectedWorker, Worker.TransformText(text, _)) {
            case Success(transformedText) => TransformCompleted(transformedText.text, text)
            case Failure(ex) => JobFailed("Processing timed out", text)
          }

ctx.ask將TextTransformed轉換成TransformCompleted。完整的Behavior定義如下:

object Frontend {

  sealed trait Event
  private case object Tick extends Event
  private final case class WorkersUpdated(newWorkers: Set[ActorRef[Worker.TransformText]]) extends Event
  private final case class TransformCompleted(originalText: String, transformedText: String) extends Event
  private final case class JobFailed(why: String, text: String) extends Event


  def apply(): Behavior[Event] = Behaviors.setup { ctx =>
    Behaviors.withTimers { timers =>
      // subscribe to available workers
      val subscriptionAdapter = ctx.messageAdapter[Receptionist.Listing] {
        case Worker.WorkerServiceKey.Listing(workers) =>
          WorkersUpdated(workers)
      }
      ctx.system.receptionist ! Receptionist.Subscribe(Worker.WorkerServiceKey, subscriptionAdapter)

      timers.startTimerWithFixedDelay(Tick, Tick, 2.seconds)

      running(ctx, IndexedSeq.empty, jobCounter = 0)
    }
  }

  private def running(ctx: ActorContext[Event], workers: IndexedSeq[ActorRef[Worker.TransformText]], jobCounter: Int): Behavior[Event] =
    Behaviors.receiveMessage {
      case WorkersUpdated(newWorkers) =>
        ctx.log.info("List of services registered with the receptionist changed: {}", newWorkers)
        running(ctx, newWorkers.toIndexedSeq, jobCounter)
      case Tick =>
        if (workers.isEmpty) {
          ctx.log.warn("Got tick request but no workers available, not sending any work")
          Behaviors.same
        } else {
          // how much time can pass before we consider a request failed
          implicit val timeout: Timeout = 5.seconds
          val selectedWorker = workers(jobCounter % workers.size)
          ctx.log.info("Sending work for processing to {}", selectedWorker)
          val text = s"hello-$jobCounter"
          ctx.ask[Worker.TransformText,Worker.TextTransformed](selectedWorker, Worker.TransformText(text, _)) {
            case Success(transformedText) => TransformCompleted(transformedText.text, text)
            case Failure(ex) => JobFailed("Processing timed out", text)
          }
          running(ctx, workers, jobCounter + 1)
        }
      case TransformCompleted(originalText, transformedText) =>
        ctx.log.info("Got completed transform of {}: {}", originalText, transformedText)
        Behaviors.same

      case JobFailed(why, text) =>
        ctx.log.warn("Transformation of text {} failed. Because: {}", text, why)
        Behaviors.same

    }

現在我們可以示範用group-router來實現某種跨節點的分散式運算。因為group-router是通過Receptionist來實現對routees管理的,而Receptionist是叢集全域性的,意味著如果我們在各節點上構建routee,然後向Receptionist登記,就會形成一個跨節點的routee ActorRef清單。如果把任務分配到這個清單上的routee上去運算,應該能實現叢集節點負載均衡的效果。下面我們就示範這個loadbalancer。流程很簡單:在一個接入點 (serviceActor)中構建workersRouter,然後3個workerRoutee並向Receptionist登記,把接到的任務分解成子任務逐個傳送給workersRouter。每個workerRoutee完成任務後將結果傳送給一個聚合器Aggregator,Aggregator在核對完成接收所有workerRoutee返回的結果後再把彙總結果返回serverActor。先看看這個serverActor:

object Service {
  val routerServiceKey = ServiceKey[WorkerRoutee.Command]("workers-router")

  sealed trait Command extends CborSerializable

  case class ProcessText(text: String) extends Command {
    require(text.nonEmpty)
  }

  case class WrappedResult(res: Aggregator.Response) extends Command

  def serviceBehavior(workersRouter: ActorRef[WorkerRoutee.Command]): Behavior[Command] = Behaviors.setup[Command] { ctx =>
    val aggregator = ctx.spawn(Aggregator(), "aggregator")
    val aggregatorRef: ActorRef[Aggregator.Response] = ctx.messageAdapter(WrappedResult)
    Behaviors.receiveMessage {
      case ProcessText(text) =>
        ctx.log.info("******************** received ProcessText command: {} ****************",text)
        val words = text.split(' ').toIndexedSeq
        aggregator ! Aggregator.CountText(words.size, aggregatorRef)
        words.foreach { word =>
          workersRouter ! WorkerRoutee.Count(word, aggregator)
        }
        Behaviors.same
      case WrappedResult(msg) =>
        msg match {
          case Aggregator.Result(res) =>
            ctx.log.info("************** mean length of words = {} **********", res)
        }
        Behaviors.same
    }
  }

  def singletonService(ctx: ActorContext[Command], workersRouter: ActorRef[WorkerRoutee.Command]) = {
    val singletonSettings = ClusterSingletonSettings(ctx.system)
      .withRole("front")
    SingletonActor(
      Behaviors.supervise(
        serviceBehavior(workersRouter)
      ).onFailure(
        SupervisorStrategy
          .restartWithBackoff(minBackoff = 10.seconds, maxBackoff = 60.seconds, randomFactor = 0.1)
          .withMaxRestarts(3)
          .withResetBackoffAfter(10.seconds)
      )
      , "singletonActor"
    ).withSettings(singletonSettings)
  }

  def apply(): Behavior[Command] = Behaviors.setup[Command] { ctx =>
    val cluster = Cluster(ctx.system)
    val workersRouter = ctx.spawn(
      Routers.group(routerServiceKey)
        .withRoundRobinRouting(),
      "workersRouter"
    )
    (0 until 3).foreach { n =>
      val routee = ctx.spawn(WorkerRoutee(cluster.selfMember.address.toString), s"work-routee-$n")
      ctx.system.receptionist ! Receptionist.register(routerServiceKey, routee)
    }
    val singletonActor = ClusterSingleton(ctx.system).init(singletonService(ctx, workersRouter))
    Behaviors.receiveMessage {
      case job@ProcessText(text) =>
        singletonActor ! job
        Behaviors.same
    }
  }

}

整體goup-router和routee的構建是在apply()裡,並把接到的任務轉發給singletonActor。singletonActor是以serviceBehavior為核心的一個actor。在servceBehavior裡把收到的任務分解並分別傳送給workersRouter。值得注意的是:serviceBehavior期望接收從Aggregator的回應,它們之間存在request/response模式資訊交流,所以需要Aggregator.Response到WrappedResult的型別轉換機制。還有:子任務是通過workersRoute傳送給個workerRoutee的,我們需要各workerRoutee把運算結果返給給Aggregator,所以傳送給workersRouter的訊息包含了Aggregator的ActorRef,如:workersRouter ! WorkerRoutee.Count(cnt,aggregatorRef)。

Aggregator是個persistentActor, 如下:

 

object Aggregator {
  sealed trait Command
  sealed trait Event extends  CborSerializable
  sealed trait Response

  case class CountText(cnt: Int, replyTo: ActorRef[Response]) extends Command
  case class MarkLength(word: String, len: Int) extends Command
  case class TextCounted(cnt: Int) extends Event
  case class LengthMarked(word: String, len: Int) extends Event
  case class Result(meanWordLength: Double) extends Response

  case class State(expectedNum: Int = 0, lens: List[Int] = Nil)

  var replyTo: ActorRef[Response] = _

  def commandHandler: (State,Command) => Effect[Event,State] = (st,cmd) => {
    cmd match {
      case CountText(cnt,ref) =>
        replyTo = ref
        Effect.persist(TextCounted(cnt))
      case MarkLength(word,len) =>
        Effect.persist(LengthMarked(word,len))
    }
  }
  def eventHandler: (State, Event) => State = (st,ev) => {
    ev match {
      case TextCounted(cnt) =>
        st.copy(expectedNum = cnt, lens = Nil)
      case LengthMarked(word,len) =>
        val state = st.copy(lens = len :: st.lens)
        if (state.lens.size >= state.expectedNum) {
          val meanWordLength = state.lens.sum.toDouble / state.lens.size
          replyTo ! Result(meanWordLength)
          State()
        } else state
    }
  }
  val takeSnapShot: (State,Event,Long) => Boolean = (st,ev,seq) => {
      if (st.lens.isEmpty) {
          if (ev.isInstanceOf[LengthMarked])
            true
          else
            false
      } else
         false
  }
  def apply(): Behavior[Command] = Behaviors.supervise(
    Behaviors.setup[Command] { ctx =>
      EventSourcedBehavior(
        persistenceId = PersistenceId("33","2333"),
        emptyState = State(),
        commandHandler = commandHandler,
        eventHandler = eventHandler
      ).onPersistFailure(
        SupervisorStrategy
          .restartWithBackoff(minBackoff = 10.seconds, maxBackoff = 60.seconds, randomFactor = 0.1)
          .withMaxRestarts(3)
          .withResetBackoffAfter(10.seconds)
      ).receiveSignal {
        case (state, RecoveryCompleted) =>
          ctx.log.info("**************Recovery Completed with state: {}***************",state)
        case (state, SnapshotCompleted(meta))  =>
          ctx.log.info("**************Snapshot Completed with state: {},id({},{})***************",state,meta.persistenceId, meta.sequenceNr)
        case (state,RecoveryFailed(err)) =>
          ctx.log.error("*************recovery failed with: {}***************",err.getMessage)
        case (state,SnapshotFailed(meta,err)) =>
          ctx.log.error("***************snapshoting failed with: {}*************",err.getMessage)
      }.snapshotWhen(takeSnapShot)
    }
  ).onFailure(
    SupervisorStrategy
      .restartWithBackoff(minBackoff = 10.seconds, maxBackoff = 60.seconds, randomFactor = 0.1)
      .withMaxRestarts(3)
      .withResetBackoffAfter(10.seconds)
  )
}

注意這個takeSnapShot函式:這個函式是在EventSourcedBehavior.snapshotWhen(takeSnapShot)呼叫的。傳入引數是(State,Event,seqenceNr),我們需要對State,Event的當前值進行分析後返回true代表做一次snapshot。

看看一部分顯示就知道任務已經分配到幾個節點上的routee:

20:06:59.072 [ClusterSystem-akka.actor.default-dispatcher-15] INFO com.learn.akka.WorkerRoutee$ - ************** processing [this] on akka://ClusterSystem@127.0.0.1:51182 ***********
20:06:59.072 [ClusterSystem-akka.actor.default-dispatcher-3] INFO com.learn.akka.WorkerRoutee$ - ************** processing [text] on akka://ClusterSystem@127.0.0.1:51182 ***********
20:06:59.072 [ClusterSystem-akka.actor.default-dispatcher-36] INFO com.learn.akka.WorkerRoutee$ - ************** processing [be] on akka://ClusterSystem@127.0.0.1:51182 ***********
20:06:59.236 [ClusterSystem-akka.actor.default-dispatcher-16] INFO com.learn.akka.WorkerRoutee$ - ************** processing [will] on akka://ClusterSystem@127.0.0.1:51173 ***********
20:06:59.236 [ClusterSystem-akka.actor.default-dispatcher-26] INFO com.learn.akka.WorkerRoutee$ - ************** processing [is] on akka://ClusterSystem@127.0.0.1:25251 ***********
20:06:59.236 [ClusterSystem-akka.actor.default-dispatcher-13] INFO com.learn.akka.WorkerRoutee$ - ************** processing [the] on akka://ClusterSystem@127.0.0.1:51173 ***********
20:06:59.236 [ClusterSystem-akka.actor.default-dispatcher-3] INFO com.learn.akka.WorkerRoutee$ - ************** processing [that] on akka://ClusterSystem@127.0.0.1:25251 ***********
20:06:59.236 [ClusterSystem-akka.actor.default-dispatcher-3] INFO com.learn.akka.WorkerRoutee$ - ************** processing [analyzed] on akka://ClusterSystem@127.0.0.1:25251 ***********

這個例子的原始碼如下:

package com.learn.akka

import akka.actor.typed._
import akka.persistence.typed._
import akka.persistence.typed.scaladsl._
import scala.concurrent.duration._
import akka.actor.typed.receptionist._
import akka.actor.typed.scaladsl.Behaviors
import akka.actor.typed.scaladsl._
import akka.cluster.typed.Cluster
import akka.cluster.typed.ClusterSingleton
import akka.cluster.typed.ClusterSingletonSettings
import akka.cluster.typed.SingletonActor
import com.typesafe.config.ConfigFactory

object WorkerRoutee {
  sealed trait Command extends CborSerializable
  case class Count(word: String, replyTo: ActorRef[Aggregator.Command]) extends Command

  def apply(nodeAddress: String): Behavior[Command] = Behaviors.setup {ctx =>
    Behaviors.receiveMessage[Command] {
      case Count(word,replyTo) =>
        ctx.log.info("************** processing [{}] on {} ***********",word,nodeAddress)
        replyTo ! Aggregator.MarkLength(word,word.length)
        Behaviors.same
    }
  }
}
object Aggregator {
  sealed trait Command
  sealed trait Event extends  CborSerializable
  sealed trait Response

  case class CountText(cnt: Int, replyTo: ActorRef[Response]) extends Command
  case class MarkLength(word: String, len: Int) extends Command
  case class TextCounted(cnt: Int) extends Event
  case class LengthMarked(word: String, len: Int) extends Event
  case class Result(meanWordLength: Double) extends Response

  case class State(expectedNum: Int = 0, lens: List[Int] = Nil)

  var replyTo: ActorRef[Response] = _

  def commandHandler: (State,Command) => Effect[Event,State] = (st,cmd) => {
    cmd match {
      case CountText(cnt,ref) =>
        replyTo = ref
        Effect.persist(TextCounted(cnt))
      case MarkLength(word,len) =>
        Effect.persist(LengthMarked(word,len))
    }
  }
  def eventHandler: (State, Event) => State = (st,ev) => {
    ev match {
      case TextCounted(cnt) =>
        st.copy(expectedNum = cnt, lens = Nil)
      case LengthMarked(word,len) =>
        val state = st.copy(lens = len :: st.lens)
        if (state.lens.size >= state.expectedNum) {
          val meanWordLength = state.lens.sum.toDouble / state.lens.size
          replyTo ! Result(meanWordLength)
          State()
        } else state
    }
  }
  val takeSnapShot: (State,Event,Long) => Boolean = (st,ev,seq) => {
      if (st.lens.isEmpty) {
          if (ev.isInstanceOf[LengthMarked])
            true
          else
            false
      } else
         false
  }
  def apply(): Behavior[Command] = Behaviors.supervise(
    Behaviors.setup[Command] { ctx =>
      EventSourcedBehavior(
        persistenceId = PersistenceId("33","2333"),
        emptyState = State(),
        commandHandler = commandHandler,
        eventHandler = eventHandler
      ).onPersistFailure(
        SupervisorStrategy
          .restartWithBackoff(minBackoff = 10.seconds, maxBackoff = 60.seconds, randomFactor = 0.1)
          .withMaxRestarts(3)
          .withResetBackoffAfter(10.seconds)
      ).receiveSignal {
        case (state, RecoveryCompleted) =>
          ctx.log.info("**************Recovery Completed with state: {}***************",state)
        case (state, SnapshotCompleted(meta))  =>
          ctx.log.info("**************Snapshot Completed with state: {},id({},{})***************",state,meta.persistenceId, meta.sequenceNr)
        case (state,RecoveryFailed(err)) =>
          ctx.log.error("*************recovery failed with: {}***************",err.getMessage)
        case (state,SnapshotFailed(meta,err)) =>
          ctx.log.error("***************snapshoting failed with: {}*************",err.getMessage)
      }.snapshotWhen(takeSnapShot)
    }
  ).onFailure(
    SupervisorStrategy
      .restartWithBackoff(minBackoff = 10.seconds, maxBackoff = 60.seconds, randomFactor = 0.1)
      .withMaxRestarts(3)
      .withResetBackoffAfter(10.seconds)
  )
}
object Service {
  val routerServiceKey = ServiceKey[WorkerRoutee.Command]("workers-router")

  sealed trait Command extends CborSerializable

  case class ProcessText(text: String) extends Command {
    require(text.nonEmpty)
  }

  case class WrappedResult(res: Aggregator.Response) extends Command

  def serviceBehavior(workersRouter: ActorRef[WorkerRoutee.Command]): Behavior[Command] = Behaviors.setup[Command] { ctx =>
    val aggregator = ctx.spawn(Aggregator(), "aggregator")
    val aggregatorRef: ActorRef[Aggregator.Response] = ctx.messageAdapter(WrappedResult)
    Behaviors.receiveMessage {
      case ProcessText(text) =>
        ctx.log.info("******************** received ProcessText command: {} ****************",text)
        val words = text.split(' ').toIndexedSeq
        aggregator ! Aggregator.CountText(words.size, aggregatorRef)
        words.foreach { word =>
          workersRouter ! WorkerRoutee.Count(word, aggregator)
        }
        Behaviors.same
      case WrappedResult(msg) =>
        msg match {
          case Aggregator.Result(res) =>
            ctx.log.info("************** mean length of words = {} **********", res)
        }
        Behaviors.same
    }
  }

  def singletonService(ctx: ActorContext[Command], workersRouter: ActorRef[WorkerRoutee.Command]) = {
    val singletonSettings = ClusterSingletonSettings(ctx.system)
      .withRole("front")
    SingletonActor(
      Behaviors.supervise(
        serviceBehavior(workersRouter)
      ).onFailure(
        SupervisorStrategy
          .restartWithBackoff(minBackoff = 10.seconds, maxBackoff = 60.seconds, randomFactor = 0.1)
          .withMaxRestarts(3)
          .withResetBackoffAfter(10.seconds)
      )
      , "singletonActor"
    ).withSettings(singletonSettings)
  }

  def apply(): Behavior[Command] = Behaviors.setup[Command] { ctx =>
    val cluster = Cluster(ctx.system)
    val workersRouter = ctx.spawn(
      Routers.group(routerServiceKey)
        .withRoundRobinRouting(),
      "workersRouter"
    )
    (0 until 3).foreach { n =>
      val routee = ctx.spawn(WorkerRoutee(cluster.selfMember.address.toString), s"work-routee-$n")
      ctx.system.receptionist ! Receptionist.register(routerServiceKey, routee)
    }
    val singletonActor = ClusterSingleton(ctx.system).init(singletonService(ctx, workersRouter))
    Behaviors.receiveMessage {
      case job@ProcessText(text) =>
        singletonActor ! job
        Behaviors.same
    }
  }

}

object LoadBalance {
  def main(args: Array[String]): Unit = {
    if (args.isEmpty) {
      startup("compute", 25251)
      startup("compute", 25252)
      startup("compute", 25253)
      startup("front", 25254)
    } else {
      require(args.size == 2, "Usage: role port")
      startup(args(0), args(1).toInt)
    }
  }

  def startup(role: String, port: Int): Unit = {
    // Override the configuration of the port when specified as program argument
    val config = ConfigFactory
      .parseString(s"""
      akka.remote.artery.canonical.port=$port
      akka.cluster.roles = [$role]
      """)
      .withFallback(ConfigFactory.load("cluster-persistence"))

    val frontEnd = ActorSystem[Service.Command](Service(), "ClusterSystem", config)
    if (role == "front") {
      println("*************** sending ProcessText command  ************")
      frontEnd ! Service.ProcessText("this is the text that will be analyzed")
    }

  }

}

cluster-persistence.conf

akka.actor.allow-java-serialization = on
akka {
  loglevel = INFO
  actor {
    provider = cluster
    serialization-bindings {
      "com.learn.akka.CborSerializable" = jackson-cbor
    }
  }
 remote {
    artery {
      canonical.hostname = "127.0.0.1"
      canonical.port = 0
    }
  }
  cluster {
    seed-nodes = [
      "akka://ClusterSystem@127.0.0.1:25251",
      "akka://ClusterSystem@127.0.0.1:25252"]
  }
  # use Cassandra to store both snapshots and the events of the persistent actors
  persistence {
    journal.plugin = "akka.persistence.cassandra.journal"
    snapshot-store.plugin = "akka.persistence.cassandra.snapshot"
  }
}
akka.persistence.cassandra {
  # don't use autocreate in production
  journal.keyspace = "poc"
  journal.keyspace-autocreate = on
  journal.tables-autocreate = on
  snapshot.keyspace = "poc_snapshot"
  snapshot.keyspace-autocreate = on
  snapshot.tables-autocreate = on
}

datastax-java-driver {
  basic.contact-points = ["192.168.11.189:9042"]
  basic.load-balancing-policy.local-datacenter = "datacenter1"
}

build.sbt

name := "learn-akka-typed"

version := "0.1"

scalaVersion := "2.13.1"
scalacOptions in Compile ++= Seq("-deprecation", "-feature", "-unchecked", "-Xlog-reflective-calls", "-Xlint")
javacOptions in Compile ++= Seq("-Xlint:unchecked", "-Xlint:deprecation")

val AkkaVersion = "2.6.5"
val AkkaPersistenceCassandraVersion = "1.0.0"


libraryDependencies ++= Seq(
  "com.typesafe.akka" %% "akka-cluster-sharding-typed" % AkkaVersion,
  "com.typesafe.akka" %% "akka-persistence-typed" % AkkaVersion,
  "com.typesafe.akka" %% "akka-persistence-query" % AkkaVersion,
  "com.typesafe.akka" %% "akka-serialization-jackson" % AkkaVersion,
  "com.typesafe.akka" %% "akka-persistence-cassandra" % AkkaPersistenceCassandraVersion,
  "com.typesafe.akka" %% "akka-slf4j" % AkkaVersion,
  "ch.qos.logback"     % "logback-classic"             % "1.2.3"
)

 

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