RabbitMQ消息模式（消费端限流 、消息的ACK与重回队列 、TTL消息 、死信队列）

1、消费端限流

什么是消费端的限流？

• 假设一个场景，首先，我们RabbitMQ服务器有上万条未处理的消息，我们随便打开一个消费者客户端，会出现下面情况：巨量的消息瞬间全部推送过来，但是我们单个客户端无法同时处理这么多数据！

消费端限流RabbitMQ提供的解决方案?

• RabbitMQ提供了一种qos（服务质量保证）功能，即在非自动确认消息的前提下，如果一定数目的消息（通过基于Consumer或者Channel设置Qos的值）未被确认前，不进行消费新的消息
• Void BasicQos(uint prefetchSize, ushort prefetchCount, bool global);
  prefetchSize：0 不限制消息大小
  prefetchCount：会告诉RabbitMQ不要同时给一个消费者推送多于N个消息，即一旦有N个消息还没有ack，则该Consumer将block（阻塞）掉，直到有消息ack
  Global：true\false是否将上面设置应用于Channel；简单来说，就是上面限制是Channel级别的还是Consumer级别

注意： prefetchSize和global这两项，RabbitMQ没有实现，暂且不研究；
prefetch_count在no_ask=false的情况下生效，即在自动应答的情况下，这两个值是不生效的；

自定义消费者：

package com.hyf.rabbitmqapi.limit;

import com.rabbitmq.client.AMQP;
import com.rabbitmq.client.Channel;
import com.rabbitmq.client.DefaultConsumer;
import com.rabbitmq.client.Envelope;

import java.io.IOException;

/**
 * @author xhy
 * @site www.4399.com
 * @company xxx公司
 * @create 2020-03-02 23:32
 */
public class MyConsumer extends DefaultConsumer {

    private  Channel channel;

    public MyConsumer(Channel channel) {
        super(channel);
        this.channel = channel;
    }

    @Override
    public void handleDelivery(String consumerTag, Envelope envelope, AMQP.BasicProperties properties, byte[] body) throws IOException {
        System.err.println("-----------consume message----------");
        System.err.println("consumerTag: " + consumerTag);
        System.err.println("envelope: " + envelope);
        System.err.println("properties: " + properties);
        System.err.println("body: " + new String(body));

        // 表示这条消息已处理完，推送下一条信息来。  false ： 代表手动签收
        channel.basicAck(envelope.getDeliveryTag(), false);

    }
}

生产端：

package com.hyf.rabbitmqapi.limit;

import com.rabbitmq.client.Channel;
import com.rabbitmq.client.Connection;
import com.rabbitmq.client.ConnectionFactory;

import java.io.IOException;

/**
 * @author xhy
 * @site www.4399.com
 * @company xxx公司
 * @create 2020-03-02 23:45
 */
public class Producer {

    public static void main(String[] args) throws Exception {
        ConnectionFactory connectionFactory = new ConnectionFactory();
        connectionFactory.setHost("192.168.59.128");
        connectionFactory.setPort(5672);
        connectionFactory.setVirtualHost("/");

        Connection connection = connectionFactory.newConnection();
        Channel channel = connection.createChannel();

        String exChangeName = "test_qos_exchange";
        String routingKey   = "qos.save";

        String msg = "消费端限流处理。。。。";

        for (int i=0;i<5;i++){
            channel.basicPublish(exChangeName,routingKey,true,null,msg.getBytes());
        }
    }
}

消费端：

package com.hyf.rabbitmqapi.limit;

import com.rabbitmq.client.Channel;
import com.rabbitmq.client.Connection;
import com.rabbitmq.client.ConnectionFactory;

import java.io.IOException;
import java.util.concurrent.TimeoutException;

/**
 * @author xhy
 * @site www.4399.com
 * @company xxx公司
 * @create 2020-03-02 23:49
 */
public class Consumer {
    public static void main(String[] args) throws IOException, TimeoutException {
        ConnectionFactory connectionFactory = new ConnectionFactory();
        connectionFactory.setHost("192.168.59.128");
        connectionFactory.setPort(5672);
        connectionFactory.setVirtualHost("/");

        Connection connection = connectionFactory.newConnection();
        Channel channel = connection.createChannel();

        String exChangeName = "test_qos_exchange";
        String exChangeType = "topic";
        String queueName    = "test_qos_queue";
        String routingKey   = "qos.#";


        channel.exchangeDeclare(exChangeName,exChangeType,true,false,null);
        channel.queueDeclare(queueName,true,false,false,null);
        channel.queueBind(queueName,exChangeName,routingKey);


        // 限流方式   第一件事就是 autoAck设置为 false
        channel.basicQos(0,1,false);

        /*
        * 参数 b：false  代表手动接收
        * */
        channel.basicConsume(queueName,false,new MyConsumer(channel));
    }
}

2、消息的ACK与重回队列

消费端手工ACK与NACK

• 消费端进行消费的时候，如果由于业务异常我们可以进行日志的记录，然后进行补偿
  如果由于服务器宕机等严重问题，那么我们就需要手工进行ACK，保障消费端消费成功！

消费端的重回队列

• 消费端重回队列是为了对没有处理成功的消息，把消息重新回递给Broker！
  一般我们在实际应用中，都会关闭重回队列，也就是设置为False；因为重回队列消息有很大概率依然会处理失败！

---

自定义消费者

package com.hyf.rabbitmqapi.ack;

import com.rabbitmq.client.AMQP;
import com.rabbitmq.client.Channel;
import com.rabbitmq.client.DefaultConsumer;
import com.rabbitmq.client.Envelope;

import java.io.IOException;

/**
 * @author xhy
 * @site www.4399.com
 * @company xxx公司
 * @create 2020-03-02 23:32
 */
public class MyConsumer extends DefaultConsumer {

    private  Channel channel;

    public MyConsumer(Channel channel) {
        super(channel);
        this.channel = channel;
    }

    @Override
    public void handleDelivery(String consumerTag, Envelope envelope, AMQP.BasicProperties properties, byte[] body) throws IOException {
        System.err.println("-----------consume message----------");
        System.err.println("body: " + new String(body));
        try {
            Thread.sleep(3000);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
        if((Integer) properties.getHeaders().get("num")==0){
            // 参数3  requeue: true 重回队列 / false  不 重回队列
            channel.basicNack(envelope.getDeliveryTag(),false,true);
        }else{
            channel.basicAck(envelope.getDeliveryTag(), false);
        }
    }
}

生产端：

package com.hyf.rabbitmqapi.ack;

import com.rabbitmq.client.AMQP;
import com.rabbitmq.client.Channel;
import com.rabbitmq.client.Connection;
import com.rabbitmq.client.ConnectionFactory;
import org.omg.CORBA.OBJ_ADAPTER;

import java.util.HashMap;
import java.util.Map;

/**
 * @author xhy
 * @site www.4399.com
 * @company xxx公司
 * @create 2020-03-02 23:45
 */
public class Producer {

    public static void main(String[] args) throws Exception {
        ConnectionFactory connectionFactory = new ConnectionFactory();
        connectionFactory.setHost("192.168.59.128");
        connectionFactory.setPort(5672);
        connectionFactory.setVirtualHost("/");

        Connection connection = connectionFactory.newConnection();
        Channel channel = connection.createChannel();

        String exChangeName = "test_ack_exchange";
        String routingKey = "ack.save";

        for (int i = 0; i < 5; i++) {
            Map<String, Object> headers = new HashMap<String, Object>();
            headers.put("num",i);
            AMQP.BasicProperties properties = new AMQP.BasicProperties.Builder()
                    .deliveryMode(2)
                    .contentEncoding("UTF-8")
                    .headers(headers)
                    .build();
            String msg = "Hello RabbitMQ ACK Message " + i;
            channel.basicPublish(exChangeName, routingKey, true, properties, msg.getBytes());
        }
    }
}

消费端：

package com.hyf.rabbitmqapi.ack;

import com.rabbitmq.client.Channel;
import com.rabbitmq.client.Connection;
import com.rabbitmq.client.ConnectionFactory;

import java.io.IOException;
import java.util.concurrent.TimeoutException;

/**
 * @author xhy
 * @site www.4399.com
 * @company xxx公司
 * @create 2020-03-02 23:49
 */
public class Consumer {
    public static void main(String[] args) throws IOException, TimeoutException {
        ConnectionFactory connectionFactory = new ConnectionFactory();
        connectionFactory.setHost("192.168.59.128");
        connectionFactory.setPort(5672);
        connectionFactory.setVirtualHost("/");

        Connection connection = connectionFactory.newConnection();
        Channel channel = connection.createChannel();

        String exChangeName = "test_ack_exchange";
        String exChangeType = "topic";
        String queueName    = "test_ack_queue";
        String routingKey   = "ack.#";


        channel.exchangeDeclare(exChangeName,exChangeType,true,false,null);
        channel.queueDeclare(queueName,true,false,false,null);
        channel.queueBind(queueName,exChangeName,routingKey);

        channel.basicConsume(queueName,false,new MyConsumer(channel));
    }
}

测试结果：
我在自定义消费者中用 0 代替消息未成功处理，其他的处理成功了，就会把它放到尾部，重新处理。

3、TTL消息

TTL是Time To Live的缩写，也就是生存时间
RabbitMQ支持消息的过期时间，在消息发送时可以进行指定
RabbitMQ支持队列的过期时间，从消息入队列开始计算，只要超过了队列的超时时间配置，那么消息自动的清除

注意：主要针对消息设置，跟交换机、队列、消费者设置毫无关系

自定义消费者：

package com.hyf.rabbitmqapi.ttl;

import com.rabbitmq.client.AMQP;
import com.rabbitmq.client.Channel;
import com.rabbitmq.client.DefaultConsumer;
import com.rabbitmq.client.Envelope;

import java.io.IOException;

/**
 * @author xhy
 * @site www.4399.com
 * @company xxx公司
 * @create 2020-03-02 23:32
 */
public class MyConsumer extends DefaultConsumer {
    public MyConsumer(Channel channel) {
        super(channel);
    }
    @Override
    public void handleDelivery(String consumerTag, Envelope envelope, AMQP.BasicProperties properties, byte[] body) throws IOException {
        System.err.println("-----------consume message----------");
        System.err.println("body: " + new String(body));

        System.out.println("headers get my1 value: "+properties.getHeaders().get("my1"));
    }
}

消费端：

package com.hyf.rabbitmqapi.ttl;

import com.rabbitmq.client.Channel;
import com.rabbitmq.client.Connection;
import com.rabbitmq.client.ConnectionFactory;

import java.io.IOException;
import java.util.concurrent.TimeoutException;

/**
 * @author xhy
 * @site www.4399.com
 * @company xxx公司
 * @create 2020-03-02 23:49
 */
public class Consumer {
    public static void main(String[] args) throws IOException, TimeoutException {
        ConnectionFactory connectionFactory = new ConnectionFactory();
        connectionFactory.setHost("192.168.59.128");
        connectionFactory.setPort(5672);
        connectionFactory.setVirtualHost("/");

        Connection connection = connectionFactory.newConnection();
        Channel channel = connection.createChannel();

        String exChangeName = "test_ttl_exchange";
        String exChangeType = "topic";
        String queueName    = "test_ttl_queue";
        String routingKey   = "ttl.#";


        channel.exchangeDeclare(exChangeName,exChangeType,true,false,null);
        channel.queueDeclare(queueName,true,false,false,null);
        channel.queueBind(queueName,exChangeName,routingKey);

        channel.basicConsume(queueName,false,new MyConsumer(channel));
    }
}

生产端：

package com.hyf.rabbitmqapi.ttl;

import com.rabbitmq.client.AMQP;
import com.rabbitmq.client.Channel;
import com.rabbitmq.client.Connection;
import com.rabbitmq.client.ConnectionFactory;

import java.util.HashMap;
import java.util.Map;

/**
 * @author xhy
 * @site www.4399.com
 * @company xxx公司
 * @create 2020-03-02 23:45
 */
public class Producer {

    public static void main(String[] args) throws Exception {
        ConnectionFactory connectionFactory = new ConnectionFactory();
        connectionFactory.setHost("192.168.59.128");
        connectionFactory.setPort(5672);
        connectionFactory.setVirtualHost("/");

        Connection connection = connectionFactory.newConnection();
        Channel channel = connection.createChannel();

        String exChangeName = "test_ttl_exchange";
        String routingKey = "ttl.save";

        Map<String, Object> headers = new HashMap<String, Object>();
        headers.put("my1","1111");
        headers.put("my2","2222");

        for (int i = 0; i < 5; i++) {
            AMQP.BasicProperties properties = new AMQP.BasicProperties.Builder()
                    .deliveryMode(2)
                    .contentEncoding("UTF-8")
                    .expiration("10000")
                    .headers(headers)
                    .build();
            String msg = "Hello RabbitMQ ttl Message " + i;
            channel.basicPublish(exChangeName, routingKey, true, properties, msg.getBytes());
        }

        //5 记得要关闭相关的连接
        channel.close();
        connection.close();

    }
}

10之后，会进行一次清空。

4、死信队列

死信队列：DLX，Dead-Letter-Exchange

• 利用DLX，当消息在一个队列中变成死信（dead message）之后，它能被重新publish到另一个Exchange，这个Exchange就是DLX

消息变成死信有以下几种情况

• 消息被拒绝（basic.reject/basic.nack）并且requeue=false
  消息TTL过期
  队列达到最大长度

死信队列的特点

• DLX也是一个正常的Exchange，和一般的Exchange没有区别，它能在任何的队列上被指定，实际上就是设置某个队列的属性；
• 当这个队列中有死信时，RabbitMQ就会自动的将这个消息重新发布到设置的Exchange上去，进而被路由到另一个队列；
• 可以监听这个队列中消息做相应的处理，这个特性可以弥补RabbitMQ3.0以前支持的immediate参数的功能；

死信队列设置

• 首先需要设置死信队列的Exchange和Queue，然后进行绑定：
  Exchange：dlx.exchange
  Queue：dlx.queue
  RoutingKey：#
• 然后我们进行正常声明交换机、队列、绑定，只不过我们需要在队列加上一个参数即可：
  Arguments.put(“x-dead-letter-exchange”,”dlx.exchange”)；
  这样消息在过期、requeue、队列在达到最大长度时，消息就可以直接路由到死信队列！

自定义消费者：

package com.hyf.rabbitmqapi.dlx;

import com.rabbitmq.client.AMQP;
import com.rabbitmq.client.Channel;
import com.rabbitmq.client.DefaultConsumer;
import com.rabbitmq.client.Envelope;

import java.io.IOException;

public class MyConsumer extends DefaultConsumer {


    public MyConsumer(Channel channel) {
        super(channel);
    }

    @Override
    public void handleDelivery(String consumerTag, Envelope envelope, AMQP.BasicProperties properties, byte[] body) throws IOException {
        System.err.println("-----------consume message----------");
        System.err.println("consumerTag: " + consumerTag);
        System.err.println("envelope: " + envelope);
        System.err.println("properties: " + properties);
        System.err.println("body: " + new String(body));
    }


}

生产端：

package com.hyf.rabbitmqapi.dlx;

import com.rabbitmq.client.AMQP;
import com.rabbitmq.client.Channel;
import com.rabbitmq.client.Connection;
import com.rabbitmq.client.ConnectionFactory;

/**
 * @author 小李飞刀
 * @site www.javaxl.com
 * @company
 * @create  2019-11-20 11:38
 */
public class Producer {
    public static void main(String[] args) throws Exception {

        ConnectionFactory connectionFactory = new ConnectionFactory();
        connectionFactory.setHost("192.168.59.128");
        connectionFactory.setPort(5672);
        connectionFactory.setVirtualHost("/");

        Connection connection = connectionFactory.newConnection();
        Channel channel = connection.createChannel();

        String exchange = "test_dlx_exchange";
        String routingKey = "dlx.save";

        String msg = "Hello RabbitMQ DLX Message";

        for(int i =0; i<1; i ++){
            AMQP.BasicProperties properties = new AMQP.BasicProperties.Builder()
                    .deliveryMode(2)
                    .contentEncoding("UTF-8")
                    .expiration("10000")
                    .build();
            channel.basicPublish(exchange, routingKey, true, properties, msg.getBytes());
        }
    }
}

消费端：

package com.hyf.rabbitmqapi.dlx;

import com.rabbitmq.client.Channel;
import com.rabbitmq.client.Connection;
import com.rabbitmq.client.ConnectionFactory;

import java.util.HashMap;
import java.util.Map;

public class Consumer {
    public static void main(String[] args) throws Exception {


        ConnectionFactory connectionFactory = new ConnectionFactory();
        connectionFactory.setHost("192.168.59.128");
        connectionFactory.setPort(5672);
        connectionFactory.setVirtualHost("/");

        Connection connection = connectionFactory.newConnection();
        Channel channel = connection.createChannel();

        // 这就是一个普通的交换机 和 队列 以及路由
        String exchangeName = "test_dlx_exchange";
        String routingKey = "dlx.#";
        String queueName = "test_dlx_queue";

        channel.exchangeDeclare(exchangeName, "topic", true, false, null);

        Map<String, Object> agruments = new HashMap<String, Object>();
        agruments.put("x-dead-letter-exchange", "dlx.exchange");
        //这个agruments属性，要设置到声明队列上
        channel.queueDeclare(queueName, true, false, false, agruments);
        channel.queueBind(queueName, exchangeName, routingKey);

        //要进行死信队列的声明:
        channel.exchangeDeclare("dlx.exchange", "topic", true, false, null);
        channel.queueDeclare("dlx.queue", true, false, false, null);
        channel.queueBind("dlx.queue", "dlx.exchange", "#");

        channel.basicConsume(queueName, true, new MyConsumer(channel));
    }
}

测试的是：消息TTL过期，进入死信队列