架构师入门笔记八 并发框架Disruptor场景应用

架构师入门笔记八 并发框架Disruptor场景应用
今天用一个停车场问题来加深对Disruptor的理解。一个有关汽车进入停车场的问题。当汽车进入停车场时，系统首先会记录汽车信息。同时也会发送消息到其他系统处理相关业务，最后发送短信通知车主收费开始。看了很多文章，里面的代码都是大同小异的，可能代码真的是很经典。以下代码也是来源网络，只是自己手动敲的，加了一些注释。

代码包含以下内容：
1） 事件对象Event
2）三个消费者Handler
3）一个生产者Processer
4）执行Main方法
Event类：汽车信息

public class MyInParkingDataEvent {

private String carLicense; // 车牌号

public String getCarLicense() {
return carLicense;
}

public void setCarLicense(String carLicense) {
this.carLicense = carLicense;
}

}

Handler类：一个负责存储汽车数据，一个负责发送kafka信息到其他系统中，最后一个负责给车主发短信通知

import com.lmax.disruptor.EventHandler;
import com.lmax.disruptor.WorkHandler;

/**
* Handler 第一个消费者，负责保存进场汽车的信息
*
*/
public class MyParkingDataInDbHandler implements EventHandler<MyInParkingDataEvent> , WorkHandler<MyInParkingDataEvent>{

@Override
public void onEvent(MyInParkingDataEvent myInParkingDataEvent) throws Exception {
long threadId = Thread.currentThread().getId(); // 获取当前线程id
String carLicense = myInParkingDataEvent.getCarLicense(); // 获取车牌号
System.out.println(String.format("Thread Id %s 保存 %s 到数据库中 ....", threadId, carLicense));
}

@Override
public void onEvent(MyInParkingDataEvent myInParkingDataEvent, long sequence, boolean endOfBatch)
throws Exception {
this.onEvent(myInParkingDataEvent);
}

}

import com.lmax.disruptor.EventHandler;

/**
* 第二个消费者，负责发送通知告知工作人员(Kafka是一种高吞吐量的分布式发布订阅消息系统)
*/
public class MyParkingDataToKafkaHandler implements EventHandler<MyInParkingDataEvent>{

@Override
public void onEvent(MyInParkingDataEvent myInParkingDataEvent, long sequence, boolean endOfBatch)
throws Exception {
long threadId = Thread.currentThread().getId(); // 获取当前线程id
String carLicense = myInParkingDataEvent.getCarLicense(); // 获取车牌号
System.out.println(String.format("Thread Id %s 发送 %s 进入停车场信息给 kafka系统...", threadId, carLicense));
}

}

import com.lmax.disruptor.EventHandler;

/**
* 第三个消费者，sms短信服务，告知司机你已经进入停车场，计费开始。
*/
public class MyParkingDataSmsHandler implements EventHandler<MyInParkingDataEvent>{

@Override
public void onEvent(MyInParkingDataEvent myInParkingDataEvent, long sequence, boolean endOfBatch)
throws Exception {
long threadId = Thread.currentThread().getId(); // 获取当前线程id
String carLicense = myInParkingDataEvent.getCarLicense(); // 获取车牌号
System.out.println(String.format("Thread Id %s 给  %s 的车主发送一条短信，并告知他计费开始了 ....", threadId, carLicense));
}

}

Producer类：负责上报停车数据

import java.util.concurrent.CountDownLatch;
import com.lmax.disruptor.EventTranslator;
import com.lmax.disruptor.dsl.Disruptor;

/**
* 生产者，进入停车场的车辆
*/
public class MyInParkingDataEventPublisher implements Runnable{

private CountDownLatch countDownLatch; // 用于监听初始化操作，等初始化执行完毕后，通知主线程继续工作
private Disruptor<MyInParkingDataEvent> disruptor;
private static final Integer NUM = 1; // 1,10,100,1000

public MyInParkingDataEventPublisher(CountDownLatch countDownLatch,
Disruptor<MyInParkingDataEvent> disruptor) {
this.countDownLatch = countDownLatch;
this.disruptor = disruptor;
}

@Override
public void run() {
MyInParkingDataEventTranslator eventTranslator = new MyInParkingDataEventTranslator();
try {
for(int i = 0; i < NUM; i ++) {
disruptor.publishEvent(eventTranslator);
Thread.sleep(1000); // 假设一秒钟进一辆车
}
} catch (InterruptedException e) {
e.printStackTrace();
} finally {
countDownLatch.countDown(); // 执行完毕后通知 await()方法
System.out.println(NUM + "辆车已经全部进入进入停车场！");
}
}

}

class MyInParkingDataEventTranslator implements EventTranslator<MyInParkingDataEvent> {

@Override
public void translateTo(MyInParkingDataEvent myInParkingDataEvent, long sequence) {
this.generateData(myInParkingDataEvent);
}

private MyInParkingDataEvent generateData(MyInParkingDataEvent myInParkingDataEvent) {
myInParkingDataEvent.setCarLicense("车牌号： 鄂A-" + (int)(Math.random() * 100000)); // 随机生成一个车牌号
System.out.println("Thread Id " + Thread.currentThread().getId() + " 写完一个event");
return myInParkingDataEvent;
}

}

执行的Main方法：

import com.lmax.disruptor.EventFactory;
import com.lmax.disruptor.YieldingWaitStrategy;
import com.lmax.disruptor.dsl.Disruptor;
import com.lmax.disruptor.dsl.EventHandlerGroup;
import com.lmax.disruptor.dsl.ProducerType;

/**
* 执行的Main方法 ，
* 一个生产者（汽车进入停车场）；
* 三个消费者（一个记录汽车信息，一个发送消息给系统，一个发送消息告知司机）
* 前两个消费者同步执行，都有结果了再执行第三个消费者
*/
public class MyInParkingDataEventMain {

public static void main(String[] args) {
long beginTime=System.currentTimeMillis();
int bufferSize = 2048; // 2的N次方
try {
// 创建线程池，负责处理Disruptor的四个消费者
ExecutorService executor = Executors.newFixedThreadPool(4);

// 初始化一个 Disruptor
Disruptor<MyInParkingDataEvent> disruptor = new Disruptor<MyInParkingDataEvent>(new EventFactory<MyInParkingDataEvent>() {
@Override
public MyInParkingDataEvent newInstance() {
return new MyInParkingDataEvent(); // Event 初始化工厂
}
}, bufferSize, executor, ProducerType.SINGLE, new YieldingWaitStrategy());

// 使用disruptor创建消费者组 MyParkingDataInDbHandler 和 MyParkingDataToKafkaHandler
EventHandlerGroup<MyInParkingDataEvent> handlerGroup = disruptor.handleEventsWith(
new MyParkingDataInDbHandler(), new MyParkingDataToKafkaHandler());

// 当上面两个消费者处理结束后在消耗 smsHandler
MyParkingDataSmsHandler myParkingDataSmsHandler = new MyParkingDataSmsHandler();
handlerGroup.then(myParkingDataSmsHandler);

// 启动Disruptor
disruptor.start();

CountDownLatch countDownLatch = new CountDownLatch(1); // 一个生产者线程准备好了就可以通知主线程继续工作了
// 生产者生成数据
executor.submit(new MyInParkingDataEventPublisher(countDownLatch, disruptor));
countDownLatch.await(); // 等待生产者结束

disruptor.shutdown();
executor.shutdown();
} catch (Exception e) {
e.printStackTrace();
}

System.out.println("总耗时:"+(System.currentTimeMillis()-beginTime));
}

}

用了两篇博客简单的介绍了Disruptor并发框架，如果想深入学习，可以到并发网里面找文章。下一章介绍BIO，NIO，AIO知识，为Netty5的入门打个基础。

学习博客：
LMAX Disruptor——一个高性能、低延迟且简单的框架
简单了解Disruptor