akka框架：（四）actor生命周期
转载：https://blog.csdn.net/liubenlong007/article/details/54093889
import akka.actor.UntypedActor;
import akka.event.Logging;
import akka.event.LoggingAdapter;
public class MyWork extends UntypedActor {
LoggingAdapter logger = Logging.getLogger(getContext().system(), this);
public static enum Msg{
WORKING, DONE, CLOSE;
}
/**
*
* /
@Override
public void preStart() {
logger.info("myWork starting.");
}
@Override
public void postStop() throws Exception {
logger.info("myWork stoping..");
}
@Override
public void onReceive(Object msg) {
try {
if(msg == Msg.WORKING){
logger.info("i am working");
}else if(msg == Msg.DONE){
logger.info("stop working");
}else if(msg == Msg.CLOSE){
logger.info("stop close");
getSender().tell(Msg.CLOSE, getSelf());
getContext().stop(getSelf());
}else {
unhandled(msg);
}
}catch (Exception e){
e.printStackTrace();
}
}
}
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import akka.actor.ActorRef;
import akka.actor.Terminated;
import akka.actor.UntypedActor;
import akka.event.Logging;
import akka.event.LoggingAdapter;
public class WatchActor extends UntypedActor {
LoggingAdapter logger = Logging.getLogger(getContext().system(), this);
/**
* 监听一个actor
* @param actorRef
*/
public WatchActor(ActorRef actorRef){
getContext().watch(actorRef);
}
@Override
public void onReceive(Object msg) throws InterruptedException {
if(msg instanceof Terminated){
//这里简单打印一下，然后停止system
logger.error(((Terminated)msg).getActor().path() + " has Terminated. now shutdown the system");
getContext().system().shutdown();
}else{
unhandled(msg);
}
}
}
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import akka.actor.ActorRef;
import akka.actor.ActorSystem;
import akka.actor.PoisonPill;
import akka.actor.Props;
import com.typesafe.config.ConfigFactory;
public class Main {
public static void main(String[] args) {
//创建ActorSystem。一般来说，一个系统只需要一个ActorSystem。
//参数1：系统名称。参数2：配置文件
ActorSystem system = ActorSystem.create("Hello", ConfigFactory.load("akka.config"));
ActorRef myWork = system.actorOf(Props.create(MyWork.class), "MyWork");
ActorRef watchActor = system.actorOf(Props.create(WatchActor.class, myWork), "WatchActor");
myWork.tell(MyWork.Msg.WORKING, ActorRef.noSender());
myWork.tell(MyWork.Msg.DONE, ActorRef.noSender());
//中断myWork
myWork.tell(PoisonPill.getInstance(), ActorRef.noSender());
}
}
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输出结果：
[INFO] [01/05/2017 15:26:15.705] [Hello-akka.actor.default-dispatcher-4] [akka://Hello/user/MyWork] myWork starting.
[INFO] [01/05/2017 15:26:15.730] [Hello-akka.actor.default-dispatcher-4] [akka://Hello/user/MyWork] i am working
[INFO] [01/05/2017 15:26:15.730] [Hello-akka.actor.default-dispatcher-4] [akka://Hello/user/MyWork] stop working
[INFO] [01/05/2017 15:26:15.736] [Hello-akka.actor.default-dispatcher-4] [akka://Hello/user/MyWork] myWork stoping..
[ERROR] [01/05/2017 15:26:15.749] [Hello-akka.actor.default-dispatcher-10] [akka://Hello/user/WatchActor] akka://Hello/user/MyWork has Terminated. now shutdown the system
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监督
这里可以对actor进行监督，在actor报出异常的时候进行处理。由于这个和生命周期也有关，所以放到这里一起说了。
akka监督策略有两种：
- OneForOneStrategy
- 只对出问题的子actor进行处理. 这是默认策略
- AllForOneStrategy
- 对子actor以及他的所有兄弟actor进行处理
定义监督者的行为：
package akka.strategy;
import akka.actor.OneForOneStrategy;
import akka.actor.Props;
import akka.actor.SupervisorStrategy;
import akka.actor.UntypedActor;
import akka.japi.Function;
import scala.concurrent.duration.Duration;
import java.util.concurrent.TimeUnit;
/**
* Created by liubenlong on 2017/1/9.
* 监督者，监督策略
*/
public class SuperVisor extends UntypedActor{
/**
* 配置自己的strategy
* @return
*/
@Override
public SupervisorStrategy supervisorStrategy(){
return new OneForOneStrategy(3, Duration.create(1, TimeUnit.MINUTES),//一分钟内重试3次，超过则kill掉actor
new Function() {
@Override
public SupervisorStrategy.Directive apply(Throwable throwable) throws Exception {
if(throwable instanceof ArithmeticException){//ArithmeticException是出现异常的运算条件时，抛出此异常。例如，一个整数“除以零”时，抛出此类的一个实例。
System.out.println("meet ArithmeticException ,just resume.");
return SupervisorStrategy.resume();//继续; 重新开始; 恢复职位;
}else if(throwable instanceof NullPointerException){
System.out.println("meet NullPointerException , restart.");
return SupervisorStrategy.restart();
}else if(throwable instanceof IllegalArgumentException){
System.out.println("meet IllegalArgumentException ,stop.");
return SupervisorStrategy.stop();
}else{
System.out.println("escalate.");
return SupervisorStrategy.escalate();//使逐步升级; 使逐步上升; 乘自动梯上升;也就是交给更上层的actor处理。抛出异常
}
}
});
}
@Override
public void onReceive(Object o) throws Throwable {
if(o instanceof Props){
getContext().actorOf((Props)o , "restartActor");
}else{
unhandled(o);
}
}
}
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定义restartActor的实现：
package akka.strategy;
import akka.actor.UntypedActor;
import scala.Option;
/**
* Created by liubenlong on 2017/1/12.
*/
public class RestartActor extends UntypedActor {
public enum Msg{
DONE, RESTART;
}
@Override
public void preStart() throws Exception {
System.out.println("preStart hashCode=" + this.hashCode());
}
@Override
public void postStop() throws Exception {
System.out.println("postStop hashCode=" + this.hashCode());
}
@Override
public void preRestart(Throwable reason, Option
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定义main方法：
package akka.strategy;
import akka.actor.*;
import com.typesafe.config.ConfigFactory;
/**
* Created by liubenlong on 2017/1/12.
*/
public class Main {
public static void main(String[] args) {
ActorSystem system = ActorSystem.create("strategy", ConfigFactory.load("akka.config"));
ActorRef superVisor = system.actorOf(Props.create(SuperVisor.class), "SuperVisor");
superVisor.tell(Props.create(RestartActor.class), ActorRef.noSender());
ActorSelection actorSelection = system.actorSelection("akka://strategy/user/SuperVisor/restartActor");//这是akka的路径。restartActor是在SuperVisor中创建的。
for(int i = 0 ; i < 100 ; i ++){
actorSelection.tell(RestartActor.Msg.RESTART, ActorRef.noSender());
}
}
}
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输出结果（省略部分异常）：
com.intellij.rt.execution.application.AppMain akka.strategy.Main
preStart hashCode=463293128
meet NullPointerException , restart.
preRestart hashCode=463293128
preStart hashCode=1195770342
postRestart hashCode=1195770342
meet NullPointerException , restart.
preRestart hashCode=1195770342
preStart hashCode=1139511720
postRestart hashCode=1139511720
meet NullPointerException , restart.
preRestart hashCode=1139511720
preStart hashCode=1906622979
postRestart hashCode=1906622979
meet NullPointerException , restart.
postStop hashCode=1906622979
[ERROR] [01/12/2017 10:52:05.563] [strategy-akka.actor.default-dispatcher-2] [akka://strategy/user/SuperVisor/restartActor] null
java.lang.NullPointerException
at akka.strategy.RestartActor.onReceive(RestartActor.java:44)
at akka.actor.UntypedActor$$anonfun$receive$1.applyOrElse(UntypedActor.scala:165)
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结果分析：
preStart是restartActor初始化时调用的，他的hashcode是463293128，接着遇到空指针异常，根据自定义策略，会重启改actor。此时会调用preRestart，注意他的hashcode依然是463293128，因为preRestart是在正式启动前在老的actor上调用的。
随后打印出preStart,说明新的actor开始创建了，他的hashcode是1195770342,新的actor实例将替代旧的实例工作，这说明同一个restartActor工作的过程中，未必真的是同一个actor。重启完成之后调用postRestart.
再经历3次（自定义策略配置的）重启以后，达到重启上限，系统将直接关闭该actor。
选择actor
上面程序中使用到了ActorSelection actorSelection = system.actorSelection("akka://strategy/user/SuperVisor/restartActor");进行actor的选择。
工作过程中可能会存在成千上万的actor，可以通过actorSelection方便的选择actor进行消息投递，其支持通配符匹配getContext().actorSelection("/user/worker_*").
参考资料
- 书籍《java高并发程序设计》
- AKKA官方文档
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