Akka之actor模型
一 定义Actor
import akka.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 MyActor extends 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.Receive import 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 ! PoisonPillcase 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.Receive import 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 ! animalsend ! humansend ! plantsend ! ufosystem.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.TimeUnit import scala.concurrent.ExecutionContext.Implicits.global import akka.actor.Actor.Receive import akka.actor._ import akka.pattern.ask import akka.pattern.pipe import akka.util.Timeout import scala.concurrent.Future 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 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 objpipe(result).to(tellActor)case "人类" =>val result:Future[Human] =for {obj <- ask(askActor,"人类").mapTo[Human]} yield objpipe(result).to(tellActor)case "植物" =>val result:Future[Plant] =for {obj <- ask(askActor,"植物").mapTo[Plant]} yield objpipe(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 objpipe(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
trait CalculatorInt {
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
import scala.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 Calculator extends 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],new Calculator), "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 += 1Some(counter)}override def postStop(): Unit = {println("[postStop] method invoked")} }
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