【scala系列】14、Akka并发变成和分布式应用程序开发

1.介绍

AKKA是java虚拟机jvm平台上构建高并发、分布式和容错应用的工具包和运行时. akka用scala语言编写，同时提供了scala和java接口

• 官网：https://akka.io/
• ActorSystem：创建并监听actor
• Actor：执行任务的角色，如果任务执行不过来可以创建下一级actor，执行具体的任务

基于akka分布式技术开发分布式应用程序，分为两种角色：master、worker

1.1 master

• 接收worker的注册，并将worker注册信息保存
• 感知worker的上下线
• 接收worker的会报心跳，更新worker的相关信息
• 定时检测超时的worker，并将超时的worker从集群中移除

1.2 worker

• 向master进行注册，加入到集群中去
• 定时向master汇报心跳

1.3 示意图

2.代码示例

2.1 导包

<!-- https://mvnrepository.com/artifact/com.typesafe.akka/akka-actor -->
 
<dependency>
 
    <groupId>com.typesafe.akka</groupId>
 
    <artifactId>akka-actor_2.11</artifactId>
 
    <version>2.3.16</version>
 
</dependency>
 
<!-- https://mvnrepository.com/artifact/com.typesafe.akka/akka-remote -->
 
<dependency>
 
    <groupId>com.typesafe.akka</groupId>
 
    <artifactId>akka-remote_2.11</artifactId>
 
    <version>2.3.16</version>
 
</dependency>

2.2 master

import java.util
 
import akka.actor.{Actor, ActorSystem, Props}
import com.typesafe.config.ConfigFactory
 
import scala.collection.mutable
import scala.concurrent.duration._
 
class Master extends Actor {
 
  /** 存放 worker 信息 */
  val id2Worker = new mutable.HashMap[String, WorkerInfo]()
  /** 存放 workerInfo */
  val workers = new mutable.HashSet[WorkerInfo]()
  //检测worker时间间隔
  val checkWorkerOutTimeIntever = 3000
  /** actor启动后会立即执行该方法 */
  override def preStart(): Unit = {
    //导入定时器
    import context.dispatcher
    //开启定时任务 parameters=>什么时候开始执行任务，执行间隔，给谁定的任务，做怎么任务
    context.system.scheduler.schedule(0 millis, checkWorkerOutTimeIntever millis, self, CheckWorkerTimeOut)
  }
 
  /** 用来收发消息的方法，这个方法会被多次执行，只要有消息过来就会被执行 */
  override def receive: Receive = {
    /** 接收到启动消息 */
    case "started" => println("master start up")
    //接收worker发送过来的worker消息，保存起来
    case RegisterWorker(wokerId, cores, memory) => {
      if (!id2Worker.contains(wokerId)) {
        //将worker 发送过来的worker信息，进行封装成WorkerInfo 保存到map和set中
        val workerInfo = new WorkerInfo(wokerId, cores, memory)
        id2Worker.put(wokerId, workerInfo)
        workers += workerInfo
        //sender  指代消息源，即谁发送过来的消息，就指代谁
        sender()!RegisteredWorker
      }
    }
    /**接收worker汇报的心跳信息*/
    case HeartBeat(workerId)=>{
    //从id2Worker 中取出对应的worker并更新最近一次汇报心跳的时间
      if(id2Worker.contains(workerId)){
        //取出wokerinfo 信息
        val workerInfo = id2Worker(workerId)
        //更新最后心跳时间
        workerInfo.lastHeartBeatTime = System.currentTimeMillis()
      }
    }
      //检测超时的worker并从列表中移除
    case CheckWorkerTimeOut=>{
      val currentTime = System.currentTimeMillis()
      //过滤出超时的worker
      val toRemove = workers.filter(w => currentTime - w.lastHeartBeatTime > checkWorkerOutTimeIntever)
      toRemove.foreach(workerInfo =>{
        id2Worker.remove(workerInfo.workerId)
        workers-=workerInfo
      })
 
      println(s"worker of alive is ${workers.size}")
    }
  }
 
}

object Master {
  def main(args: Array[String]): Unit = {
    val masterHost = "localhost"
    val masterPort = "8081"
 
    val configStr =
      s"""
         |akka.actor.provider = "akka.remote.RemoteActorRefProvider"
         |akka.remote.netty.tcp.hostname = "$masterHost"
         |akka.remote.netty.tcp.port = "$masterPort"
      """.stripMargin
    val config = ConfigFactory.parseString(configStr)
    //创建ActorSystem
    val masterActorSystem = ActorSystem("masterActorSystem", config)
    //创建actor
    val masterActor = masterActorSystem.actorOf(Props[Master], "masterActor")
    //给新创建的master发送一条消息(发送消息用感叹号 "!" 进行发送)
    masterActor ! "started"
    //将ActorSystem 阻塞在这，不要让其停止掉
    masterActorSystem.awaitTermination()
    //masterActorSystem.whenTerminated
  }
}

2.3 RemoteMessage

trait RemoteMessage extends Serializable{}
 
/**worker 向master 发送消息，注册*/
case class RegisterWorker(var wokerId:String,var cores:Int,var memory:Int) extends RemoteMessage
/**master 向 worker 发送的消息*/
case class RegisteredWorker() extends  RemoteMessage
 
/**worker 给自己发送的消息*/
object SendHeartBeat
 
/**worker 向master发送心跳消息*/
case class HeartBeat(var workerId:String)
/**master 向自己发送消息 定时检测超时worker*/
object CheckWorkerTimeOut

2.4 Worker

import java.util.UUID
 
import akka.actor.{Actor, ActorSelection, ActorSystem, Props}
import com.typesafe.config.ConfigFactory
import scala.concurrent.duration._
 
class Worker(var cores: Int, var memory: Int) extends Actor {
  var masterActor: ActorSelection = null
  /** 用来收发消息的方法，这个方法会被多次执行，只要有消息过来就会被执行 */
 
 
  val workerId = UUID.randomUUID().toString
  //心跳时间间隔
  val heartBeatIntever = 3000
 
  /** * actor启动后会立即执行该方法 */
  override def preStart(): Unit = {
    /** 获取masterActorSystem的地址 */
    masterActor = context.actorSelection("akka.tcp://masterActorSystem@localhost:8081/user/masterActor")
    //启动后立即向master注册信息
    masterActor ! RegisterWorker(workerId, cores, memory)
  }
 
  override def receive: Receive = {
    /** 接收到启动消息 */
    case "started" => println("worker start up")
 
    /** 接收到master发送过来的worker注册成功的消息 */
    case RegisteredWorker => {
      //导入定时器
      import context.dispatcher
      //开启定时任务 parameters=>什么时候开始执行任务，执行间隔，给谁定的任务，做怎么任务
      context.system.scheduler.schedule(0 millis, heartBeatIntever millis, self, SendHeartBeat)
    }
    /** 向master汇报心跳 */
    case SendHeartBeat => {
      masterActor!HeartBeat(workerId)
    }
  }
 
}

/**
  * 用来封装worker的基本信息
  * @param workerId
  * @param cores
  * @param memory
  */
class WorkerInfo(var workerId:String,var cores:Int,var memory:Int) extends Serializable {
  /**worker 最近一次汇报心跳的时间*/
  var lastHeartBeatTime:Long = System.currentTimeMillis()
}