Akka之actor模型

一 定义Actor

importakka.actor.{Props, ActorSystem, Actor}
import akka.actor.Actor.Receive
import akka.event.Logging

/** 通过扩展Actor并实现receive方法来定义Actor*/
class MyActorextends Actor{
    //获取LoggingAdapter，用于日志输出
    val log = Logging(context.system,this)
    def receive = {
        case "test"=> log.info("Received Test")
        case _ => log.info("Received Unknown Message")
    }
}

object MyActor extends App {
    /*ActorSystem 用于创建维护Actor*/
    val system = ActorSystem("MyActorSystem")
    /*返回ActorSystem的LoggingAdpater*/
    val systemLog= system.log
    /*通过ActorSystem#actorOf创建MyActor指定名称为myactor*/
    val myactor = system.actorOf(Props[MyActor],name="myactor")
    systemLog.info("准备向myactor发送消息")
    /*向myactor发送消息*/
    myactor !"test"
    myactor !"123"
    /*关闭ActorSystem，停止程序的运行*/
    system.shutdown()
}

 

二 ActorSystem

ActorSystem的只要职责：

# 创建Actor 和 ActorRef

# 返回Actor Ref

# 拦截消息，并把它发到邮箱(临时存储消息的地方)

 

创建ActorRef

system.actorOf(Props[MyActor],name="myactor")

我们可以在Props[Actor]放入一个Actor类型，也可以放入一一个Actor引用，但是这种是不推荐的

使用ActorRef对象可以进行消息的发送等操作

 

三 2种创建Actor的方式

3.1 ActorSystem 创建Actor

val system = ActorSystem("mySystem")

val myActor = system.actorOf(Props[MyActor],"myactor2")

通过ActorSystem创建的Actor是顶级Actor，在Akka框架中，每一个Akka应用程序都会有一个守卫Actor（guardian）user,所有通过system.actorOf工厂方法创建的Actor都是user的子Actor,也是整Akka程序的顶级Actor

 

3.2 通过context创建Actor

我们可以通过Actor上下文创建子Actor，使得父Actor拥有管理子Actor的能力

import akka.actor.Actor.Receiveimport akka.actor.{ActorLogging,Actor,Props}class ContextActor extends Actor with ActorLogging{    val childActor = context.actorOf(Props[MyActor], name = "ChildActor")    def receive: Receive = {        case msg =>            childActor !msg;            log.info("Received "+msg)    }}

object MyActor extends App {    /*ActorSystem 用于创建维护Actor*/    val system = ActorSystem("MyActorSystem")    /*返回ActorSystem的LoggingAdpater*/    val systemLog = system.log    /*通过ActorSystem#actorOf创建MyActor指定名称为myactor的顶级Actor*/    val myactor = system.actorOf(Props[MyActor],name="topActor")    systemLog.info("准备向Top Actor--MyActor发送消息")    /*向myactor发送消息*/    myactor ! "test"    myactor ! "123"    /*通过ActorSystem#actorOf创建ContextActor,然后在其内部创建一个子的MyActor*/    val contextActor = system.actorOf(Props[ContextActor],name="childActor")    systemLog.info("准备向Child Actor--MyActor发送消息")    contextActor ! "hadoop"    contextActor ! "hive"    /*关闭ActorSystem，停止程序的运行*/    system.shutdown()}

 

得到的结果如下：

准备向TopActor--MyActor发送消息

[akka://MyActorSystem/user/topActor] Received Test

[akka://MyActorSystem/user/topActor] ReceivedUnknown Message

准备向ChildActor--MyActor发送消息

[akka://MyActorSystem/user/childActor/ChildActor]Received Unknown Message

[akka://MyActorSystem/user/childActor] Receivedhadoop

[akka://MyActorSystem/user/childActor] Receivedhive

[akka://MyActorSystem/user/childActor/ChildActor]Received Unknown Message

 

结论：通过context创建子的Actor这种方式，可以支持链式调用

 

四 Actor的path

通过以上运行的结论：

akka://MyActorSystem/user/topActor

akka://MyActorSystem/user/childActor/ChildActor

 

五 Actor API的使用

5.1 hook方法

preStart，postStop方法

import akka.actor._import akka.actor.Actor.Receiveclass HookActor extends Actor with ActorLogging{    var child:ActorRef = _    /*preStart()，Actor启动之前调用，用于完成初始化工作*/    @throws[Exception](classOf[Exception])    override def preStart(): Unit = {        log.info("[preStrat method invoked]")        child = context.actorOf(Props[MyActor],name="myChild")    }    def receive: Receive = {        case msg => child ! msg;log.info("Received "+msg)    }    /*postStop()，Actor停止之后调用*/    @throws[Exception](classOf[Exception])    override def postStop(): Unit = {        log.info("[postStop method invoked]")        context.stop(child)    }}object HookActor extends App {    val system = ActorSystem("HookActorSystem")    val hook = system.actorOf(Props[HookActor],name="hook")    hook ! "Welcome You"    hook ! "Nice to meet you"    system.terminate()}

 

5.2成员变量self及成员方法sender方法的使用

self ! 消息：指的是自己向自己发送一条消息

sender ! 或者 sender() !消息　指定的是向给自己发送消息的Actor发送一条消息，如果没有给自己发送消息的Actor，则不会投递消息

class MyActor extends Actor{    self ! "MSG FROM MYSELF"    //获取LoggingAdapter，用于日志输出    val log = Logging(context.system,this)    def receive = {        case "test" =>            log.info("[MyActor]=> test")            sender()!"MSG FROM MyActor"        case "MSG FROM MYSELF" =>            log.info("[MyActor]=> MSG FROM MYSELF")        case "MSG FROM MyActor" =>            log.info("[MyActor]=>MSG FROM MyActor")        case _ => log.info("[MyActor]=> Unkown Message");    }}object MyActor extends App {    /*ActorSystem 用于创建维护Actor*/    val system = ActorSystem("MyActorSystem")    /*返回ActorSystem的LoggingAdpater*/    val systemLog = system.log    /*通过ActorSystem#actorOf创建MyActor指定名称为myactor的顶级Actor*///    val myactor = system.actorOf(Props[MyActor],name="topActor")//    systemLog.info("准备向Top Actor--MyActor发送消息")//    /*向myactor发送消息*///    myactor ! "test"    /*通过ActorSystem#actorOf创建ContextActor,然后在其内部创建一个子的MyActor*/    val contextActor = system.actorOf(Props[ContextActor],name="childActor")    systemLog.info("准备向Child Actor--MyActor发送消息")    contextActor ! "test"    /*关闭ActorSystem，停止程序的运行*/    system.shutdown()}

 

class ContextActor extends Actor with ActorLogging{    val childActor = context.actorOf(Props[MyActor], name = "ChildActor")    def receive: Receive = {        case msg =>            childActor ! msg;            log.info("[ContextActor]=> "+msg)    }}

 

[akka://MyActorSystem/user/childActor][ContextActor]=> test

[akka://MyActorSystem/user/childActor/ChildActor][MyActor]=> MSG FROM MYSELF

[akka://MyActorSystem/user/childActor/ChildActor][MyActor]=> test

[akka://MyActorSystem/user/childActor/ChildActor][MyActor]=>MSG FROM MyActor

[akka://MyActorSystem/user/childActor][ContextActor]=> MSG FROM MyActor

 

5.3 unhandle方法的使用

unhandled方法用于处理没有被receive方法处理的消息，比如case 中并没有针对没有匹配的消息的处理case _ 语句，在实际开发过程中，可能会对不能被处理的消息增加一些应对逻辑，此时可以重写unhandled方法

class UnhandleActor extends Actor with ActorLogging{    def receive = {        case "hello" => println("hello, nice to meet you!")    }    /*重写unhandled方法*/    override def unhandled(message: Any): Unit = {        log.info("UNHANDLED MSG {}",message.toString.toUpperCase())    }}object UnhandleActor {    def main(args: Array[String]) {        val system = ActorSystem("UnhandleActor")        val unhandle = system.actorOf(Props[UnhandleActor],name="unhandle")        unhandle ! "hello"        unhandle ! "business dias"    }}

 

 

六 Actor的停止

6.1 通过ActorSystem#shutdown(过时) 或者ActorSystem#terminate

停止所有Actor运行

object UnhandleActor {    def main(args: Array[String]) {        val system = ActorSystem("UnhandleActor")        val unhandle = system.actorOf(Props[UnhandleActor],name="unhandle")        unhandle ! "hello"        unhandle ! "business dias"        //system.shutdown()        system.terminate()    }}

 

6.2 通过ActorContext停止某一个Actor

class HookActor extends Actor with ActorLogging{    var child:ActorRef = _    /*preStart()，Actor启动之前调用，用于完成初始化工作*/    @throws[Exception](classOf[Exception])    override def preStart(): Unit = {        log.info("[preStrat method invoked]")        child = context.actorOf(Props[MyActor],name="myChild")    }    def receive: Receive = {        case "self" => sender() ! "test"        case msg => child ! msg;log.info("Received "+msg)    }    /*postStop()，Actor停止之后调用*/    @throws[Exception](classOf[Exception])    override def postStop(): Unit = {        log.info("[postStop method invoked]")        context.stop(child)    }}

 

6.3 通过发送消息的形式通知Actor关闭

语法格式 actor ! PoisonPill

class MyActor extends Actor{    //获取LoggingAdapter，用于日志输出    val log = Logging(context.system,this)    def receive = {        case "test" =>            log.info("[MyActor]=> test")            sender()!"MSG FROM MyActor"        case _ =>            log.info("[MyActor]=> Unkown Message");    }    @throws[Exception](classOf[Exception])    override def postStop(): Unit = {        log.info("[MyActor][postStop method invoked]")    }}

class HookActor extends Actor with ActorLogging{    var child:ActorRef = context.actorOf(Props[MyActor],name="myChild")    def receive: Receive = {        case "stop" => child ! PoisonPill        case msg => child ! msg;log.info("[HookActor]=> "+msg)    }}object HookActor extends App {    val system = ActorSystem("HookActorSystem")    val hook = system.actorOf(Props[HookActor],name="hook")    hook ! "Nice to meet you"    hook ! "stop"}

 

 

 

七 Actor 消息模型

Akka中，消息可以以2种模型来传递给Actor, 如下：

7.1 Fire and Forget

消息生产者不期望从消费者得到答复，这种消息是异步方式发送，然后立即返回，Akka actors使用tell()方法指示该消息是Fire and Forget模式

import akka.actor.Actor.Receiveimport akka.actor.{ActorSystem, Props, ActorLogging, Actor}case class Animal(msg:String)case class Human(msg:String)case class Plant(msg:String)case class UFO(msg:String)class FireAndForgetActor extends Actor with ActorLogging{    def receive: Receive = {        case Animal(msg) => log.info("[Animal] => {}", msg)        case Human(msg) => log.info("[Human] => {}", msg)        case Plant(msg) => log.info("[Plant] => {}", msg)        case _ => log.info("Hahah")    }}class SendActor extends Actor with ActorLogging{    val child = context.actorOf(Props[FireAndForgetActor],name="tell")    def receive: Receive = {        case msg => child.tell(msg,sender)    }    override def unhandled(message: Any): Unit = {        log.info("[Unhandled Message] => {}",message)    }}object SendActor extends App {    val system = ActorSystem("SendActorSystem")    val send = system.actorOf(Props[SendActor],name="send")    val animal = new Animal("我是老虎")    val human = new Human("我是隔壁那啥")    val plant = new Plant("我是小草")    val ufo = new UFO("我是来自xxx星球的")    send ! animal    send ! human    send ! plant    send ! ufo    system.terminate()}

 

7.2 Send and Receive

这种模式，生产者期望从消费者得到一个答复，而且需要等这个答复，这种模式也是异步发送的，返回一个Future, kka actors 使用ask()方法发送消息然后等待答复的future

 

import java.util.concurrent.TimeUnitimport scala.concurrent.ExecutionContext.Implicits.globalimport akka.actor.Actor.Receiveimport akka.actor._import akka.pattern.askimport akka.pattern.pipeimport akka.util.Timeoutimport scala.concurrent.Futurecase class Animal(msg:String)case class Human(msg:String)case class Plant(msg:String)case class UFO(msg:String)class FireAndForgetActor extends Actor with ActorLogging{    def receive: Receive = {        case Animal(msg) => log.info("[Animal] => {}", msg)        case Human(msg) => log.info("[Human] => {}", msg)        case Plant(msg) => log.info("[Plant] => {}", msg)        case _ => log.info("Hahah")    }}class SendAndReceiveActor extends Actor with ActorLogging{    def receive: Receive = {        case "动物" =>            sender ! new Animal("老虎")        case "人类" =>            sender ! new Human("小明")        case "植物" =>            sender ! new Plant("杜鹃花")        case _ =>            sender ! new UFO("UFO")    }}class RunActor extends Actor with ActorLogging{    implicit val timeout = Timeout(5,TimeUnit.MILLISECONDS)    val askActor = context.actorOf(Props[SendAndReceiveActor],name="ask")    val tellActor = context.actorOf(Props[FireAndForgetActor],name="tell")    def receive: Receive = {        case "动物" =>            val result:Future[Animal] =                for {                    obj <- ask(askActor,"动物").mapTo[Animal]                } yield obj            pipe(result).to(tellActor)        case "人类" =>            val result:Future[Human] =                for {                    obj <- ask(askActor,"人类").mapTo[Human]                } yield obj            pipe(result).to(tellActor)        case "植物" =>            val result:Future[Plant] =                for {                    obj <- ask(askActor,"植物").mapTo[Plant]                } yield obj            pipe(result).to(tellActor)        case "不明飞行物" =>            val result:Future[UFO] =                for {                    obj <- ask(askActor,"不明飞行物").mapTo[UFO]                } yield obj            pipe(result).to(tellActor)    }}class SendActor extends Actor with ActorLogging{    val child = context.actorOf(Props[FireAndForgetActor],name="tell")    def receive: Receive = {        case msg => child.tell(msg,sender)    }    override def unhandled(message: Any): Unit = {        log.info("[Unhandled Message] => {}",message)    }}object SendActor extends App {    val system = ActorSystem("SendActorSystem")    val send = system.actorOf(Props[RunActor],name="send")    send ! "动物"    send ! "人类"    send ! "植物"    send ! "不明飞行物"    Thread.sleep(2000)    system.terminate()}

 

注意点：

必须声明一个隐式timeout参数：

implicit val timeout = Timeout(5,TimeUnit.

MILLISECONDS)

 

必须引入import scala.concurrent.ExecutionContext.

Implicits.global

 

ask 方法不是Actor自己，需要引入import akka.pattern.ask

pipe也不是Actor自己的也需要引入：import

akka.pattern.pipe

 

 

八  Typed Actor

8.1 什么是Typed Actor

Typed Actor是Active Objects设计模式的实现. Active Objects模式将方法的执行和方法的调用进行解耦合，从而为程序引入并发性。Typed Actor由公用的接口和对应实现两部分构成

我们来看看Active Object模式是怎么实现解耦的：

# 客户端调用代理对象的方法

# 代理对象不断传递方法调用作为Method Request到一个调度器或者Invocation Handler去拦截这些请求

# 调度器Scheduler或者InvocationHandler将Method Request放入队列

# 调度器连续不断的监控队列，然后决定哪一个Method Request是可以运行的，如果被调用了，则从队列中移除

# Scheduler或者Invocation Handler分发Method Request 到 这个方法实现类（implementationobject）

# 这个实现类和运行Scheduler处于相同的线程，处理请求然后与返回客户端Future

 

8.2 创建Type Actor,并发送消息

第一步： 先定义接口或者特质

traitCalculatorInt {
    def add(first:Int,second:Int):Future[Int]
    def subtract(first:Int,second:Int):Future[Int]
    def incrementCount():Unit
}

第二步：继承Trait,并实现方法

importscala.concurrent.{Promise, Future}
import akka.actor.TypedActor.dispatcher
/**
 * Future:表示一个可能还没有实际完成的异步任务的结果
 * 为了使Future完全非阻塞，注册Callback到Future中，一旦future完成，Callback会被异步执行
 * Promise:是一个可写的，只能赋一次值的容器，Promise存储计算结果，从Promise中可以得到Future，
 * 由Promise来完成Future.　也可以从字面上来理解，Promise也就是一个承诺，就好比去买一杯咖啡，
 * 付账过后，服务员承诺会给你一杯咖啡，但需要过几分钟才能领取这杯咖啡．服务员制作咖啡的过程就是
 * 一个Future，而付账过后，就得到服务员的一个Promise。
 */
class Calculatorextends CalculatorInt{
    var counter  = 0;

    def add(first: Int,second: Int): Future[Int] = {
        Promise.successful[Int](first+ second).future
    }

    def subtract(first: Int,second: Int): Future[Int] = {
        Promise.successful[Int](first- second).future
    }

    def incrementCount(): Unit = {
        counter += 1
        Some(counter)
    }
}

 

第三步 创建TypeActor

# 方式一：直接通过默认的构造函数创建Typed Actor

 

val_system = ActorSystem("TypedActorsExample")
val c:CalculatorInt= TypedActor(_system).typedActorOf(TypedProps[Calculator]())

# 方式二：直接通过默认的构造函数创建Typed Actor并指定Typed Actor名称

val c1:CalculatorInt= TypedActor(_system).typedActorOf(TypedProps[Calculator](),"myCalculator")

方式三：通过非默认的构造函数创建Typed Actor并指定Typed Actor名称
val c2:CalculatorInt= TypedActor(_system).typedActorOf(TypedProps(classOf[CalculatorInt],newCalculator), "myCalculator")

 

第四步 ： 发送消息

第一种：Fire and Forget

c.incrementCount()

 

第二种：Send and Receive

val future = c.add(14,6)val durations = Duration.apply(5,TimeUnit.SECONDS);val result = Await.result(future,durations)

 

 

8.3 停止Type Actor

有两种方式停止Type Actor:

TypedActor(_system).stop(c)TypedActor(_system).poisonPill(c)

 

 

 

8.4 Type Actor 声明周期监控

通过实现TypeActor.PreStart和TypeActor.PostStop接口，在actor开始和结束的时候，我们可以添加一些功能

class Calculator extends CalculatorInt with PreStart with PostStop{    var counter  = 0;    override def preStart(): Unit = {        println("[preStart] method invoked")    }    def add(first: Int, second: Int): Future[Int] = {        Promise.successful[Int](first + second).future    }    def subtract(first: Int, second: Int): Future[Int] = {        Promise.successful[Int](first - second).future    }    def incrementCount(): Unit = {        counter += 1        Some(counter)    }        override def postStop(): Unit = {        println("[postStop] method invoked")    }}