akka框架：（十）agent
转载：https://blog.csdn.net/liubenlong007/article/details/54576611
我们知道在JDK中，编写多线程代码时要谨慎处理临界区的数据，可以加锁或者使用JDK自带的CAS库：atomic相关包。
那么在akka中怎么处理呢？akka给我们提供了一个agent。可以使用agent来实现共享变量的安全处理。
下面示例为10个actor并发累加countAgent变量。每个累加10000次。如果正确的话，最终结果应该是10W。
package akka;
import akka.actor.*;
import akka.agent.Agent;
import akka.dispatch.ExecutionContexts;
import akka.dispatch.Futures;
import akka.dispatch.Mapper;
import akka.dispatch.OnComplete;
import akka.event.Logging;
import akka.event.LoggingAdapter;
import com.typesafe.config.ConfigFactory;
import scala.concurrent.Future;
import scala.concurrent.duration.Duration;
import java.util.concurrent.ConcurrentLinkedQueue;
import java.util.concurrent.CountDownLatch;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.TimeoutException;
import java.util.concurrent.atomic.AtomicInteger;
/**
* Created by liubenlong on 2017/1/12.
*/
public class AgentTest extends UntypedActor {
private final LoggingAdapter log = Logging.getLogger(getContext().system(), this);
@Override
public void onReceive(Object o) throws Throwable {
if(o instanceof Integer){
for(int i = 0 ; i < 10000 ; i ++){
Future future = countAgent.alter(new Mapper() {
@Override
public Integer apply(Integer parameter) {
return parameter + 1;
}
});
queue.add(future);
}
getContext().stop(getSelf());//完成任务，关闭自己
}else{
unhandled(o);
}
}
public static CountDownLatch latch = new CountDownLatch(10);
public static Agent countAgent = Agent.create(0, ExecutionContexts.global());
public static ConcurrentLinkedQueue> queue = new ConcurrentLinkedQueue<>();
public static void main(String [] args) throws InterruptedException, TimeoutException {
ActorSystem system = ActorSystem.create("inbox", ConfigFactory.load("akka.conf"));
ActorRef[] actorRefs = new ActorRef[10];
for(int i = 0 ; i < 10 ; i ++){
actorRefs[i] = system.actorOf(Props.create(AgentTest.class), "AgentTest" + i);
}
Inbox inbox = Inbox.create(system);
for (ActorRef ref : actorRefs) {
inbox.send(ref, 1);
inbox.watch(ref);
}
System.out.println("countAgent 1:" + countAgent.get());
/*
* 这里本来想用JDK里的AtomicInteger, 但是不行，不适用于这里的actor
*/
//等待所有actor执行完毕
int closeCount = 0;
while(true){
Object o = inbox.receive(Duration.create(1, TimeUnit.SECONDS));
if(o instanceof Terminated){
closeCount ++;
if(closeCount == actorRefs.length){
break;
}
}else{
System.out.println("o:" + o);
}
}
System.out.println("countAgent 2:" + countAgent.get());
//等待所有累加线程完成
Futures.sequence(queue, system.dispatcher()).onComplete(new OnComplete>() {
@Override
public void onComplete(Throwable throwable, Iterable integers) throws Throwable {
System.out.println("countAgent 3:" + countAgent.get());
system.shutdown();
}
}, system.dispatcher());
}
}
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运行结果：
countAgent 1:0
countAgent 2:10
countAgent 3:100000
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参考资料
- 书籍《java高并发程序设计》
- AKKA官方文档