关于rabbitmq:二RabbitMQ消息分发机制

咱们晓得每个音讯的解决工夫是不同的，换句话说音讯的复杂度是不同的，有些音讯很简单，须要很久的工夫，有些音讯很简略，只需耗时一会就能够实现，而在理论状况下如何分配资源，让效率达到最大化，从而实现按能力分配任务，达到物尽其用。这就须要音讯的散发机制。

一、Fair dispatch(偏心散发)

这里咱们创立 DistributionSender.java 和 DistributionReceiver.java 来模仿发送者和接收者。
DistributionSender.java

@Component
public class DistributionSender {

    @Autowired
    private AmqpTemplate rabbitTemplate;

    public void send(int i) {
        // 发送的音讯
        String message = "This is a task, and the complexity is" + i + "。" + StringUtils.repeat(".", i);
        this.rabbitTemplate.convertAndSend("distribu", message);
    }
}

应用默认交换机，队列为“distribu”

    /**
     * 申明 distribu 队列
     * 
     * @return
     */
    @Bean
    public Queue DistribuQueue() {return new Queue("distribu");
    }

java 和 DistributionReceiver.java

@Component
public class DistributionReceiver {


    /**
     * 消费者 A
     * 
     * @param msg
     */
    @SuppressWarnings("deprecation")
    @RabbitListener(queues = "distribu")
    public void processA(Message message) {String msg = new String(message.getBody());
        System.out.println("DistributionReceiverA  :" + msg);
        SimpleDateFormat time = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss:SSSS");
        System.out.println("ProccessingA... at" + time.format(new Date()));

        try {for (char ch : msg.toCharArray()) {if (ch == '.') {doWork(1000);
                }
            }
        } catch (InterruptedException e) { } finally {System.out.println("A Done! at" + time.format(new Date()));
        }
    }

    private void doWork(long time) throws InterruptedException {Thread.sleep(time);
    }

}

增加 RabbitTest.java 文件模仿申请

@Controller
public class RabbitTest{

    @Autowired
    private DistributionSender distributionSender;

    /**
     * 散发机制音讯发送测试
     */
    @GetMapping("/distribu")
    public void distribu() {distributionSender.send(3);
    }
}

运行程序，拜访 http://localhost:8080/rabbit/…，能够失去上面的打印的信息：

 DistributionReceiverA  : This is a task, and the complexity is 3。...
 ProccessingA... at 2018-05-23 21:29:18:0628
 A Done! at 2018-05-23 21:29:21:0639

从打印的信息能够看出这里就模仿了实现工作须要 3 秒钟的工夫工作实现。

上面咱们更改发送的音讯数量，在 controller 控制器外面进行更改，如下：

    /**
     * 散发机制音讯发送测试
     */
    @GetMapping("/distribu")
    public void distribu() {for (int i = 0; i < 5; i++) {
            // 发送工作复杂度都为 1 的音讯
            distributionSender.send(1);
        }
    }

模仿发送 5 条音讯，并且每条发送的音讯的复杂度都是雷同的，复杂度都为 1。

而后再在 receiver 包中 DistributionReceiver.java 新增一个消费者 B，如下：

/**
     * 消费者 B
     * 
     * @param msg
     */
    @SuppressWarnings("deprecation")
    @RabbitListener(queues = "distribu")
    public void processB(Message message) {String msg = new String(message.getBody());
        System.out.println("DistributionReceiverB  :" + msg);
        SimpleDateFormat time = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss:SSSS");
        System.out.println("ProccessingB... at" + time.format(new Date()));

        try {for (char ch : msg.toCharArray()) {if (ch == '.') {doWork(1000);
                }
            }
        } catch (InterruptedException e) { } finally {System.out.println("B Done! at" + time.format(new Date()));
        }
    }

再次运行程序，拜访接口，后果如下：

 DistributionReceiverA  : This is a task, and the complexity is 1。.
 ProccessingA... at 2018-05-22 23:23:43:0014
 DistributionReceiverB  : This is a task, and the complexity is 1。.
 ProccessingB... at 2018-05-22 23:23:43:0014
 A Done! at 2018-05-22 23:23:44:0017
 B Done! at 2018-05-22 23:23:44:0017
 DistributionReceiverA  : This is a task, and the complexity is 1。.
 DistributionReceiverB  : This is a task, and the complexity is 1。.
 ProccessingA... at 2018-05-22 23:23:44:0093
 ProccessingB... at 2018-05-22 23:23:44:0093
 A Done! at 2018-05-22 23:23:45:0095
 B Done! at 2018-05-22 23:23:45:0095
 DistributionReceiverB  : This is a task, and the complexity is 1。.
 ProccessingB... at 2018-05-22 23:23:45:0143
 B Done! at 2018-05-22 23:23:46:0148

在音讯雷同，A、B 解决能力一样状况下，咱们能够发现 A、B 简直是同时解决音讯，音讯发送程序为 A ->B->A->B->B。能够看出这里并没有实现 A 与 B 均匀轮询的状况，在最初的状况 B 执行了两次。

接着当初咱们把 A 解决能力更改为每个点要 Thread.sleep(4000）, B 为 Thread.sleep(1000），就是 B 的解决能力是 A 的四倍。运行一下，咱们看一下打印的后果：

DistributionReceiverB  : This is a task, and the complexity is 1。.
 ProccessingB... at 2018-05-22 23:24:48:0623
 DistributionReceiverA  : This is a task, and the complexity is 1。.
 ProccessingA... at 2018-05-22 23:24:48:0623
 B Done! at 2018-05-22 23:24:49:0624
 DistributionReceiverB  : This is a task, and the complexity is 1。.
 ProccessingB... at 2018-05-22 23:24:49:0663
 B Done! at 2018-05-22 23:24:50:0664
 DistributionReceiverB  : This is a task, and the complexity is 1。.
 ProccessingB... at 2018-05-22 23:24:50:0704
 B Done! at 2018-05-22 23:24:51:0709
 DistributionReceiverB  : This is a task, and the complexity is 1。.
 ProccessingB... at 2018-05-22 23:24:51:0748
 A Done! at 2018-05-22 23:24:52:0629
 B Done! at 2018-05-22 23:24:52:0749

当初咱们能够清晰地看到在这里 B 解决了 4 条音讯，而 A 只解决了 1 条音讯。这里就是按偏心散发的机制来发送音讯的，即按消费者解决能力来散发音讯。
这就是偏心散发。

二、Round-robin dispatch(轮询散发)

相较于偏心散发而言，轮询散发即不去判断消费者的解决速率，也不思考每个工作的时长，依照轮流排序的形式，把工作一一发给消费者，并且是提前一次性调配，并非一个一个调配。