RabbitMQ:死信队列

Tin

2022-6-19

RabbitMQ

死信的概念

无法被消费的消息

应用场景:为了保证订单业务的消息数据不丢失，需要使用到 RabbitMQ 的死信队列机制，当消息消费发生异常时，将消息投入死信队列中.还有比如说: 用户在商城下单成功并点击去支付后在指定时间未支付时自动失效

死信的来源

消息 TTL 过期
队列达到最大长度(队列满了，无法再添加数据到 mq 中)
消息被拒绝(basic.reject 或 basic.nack)并且 requeue=false.

死信实战

代码架构图

消息TTL 过期

Consume01

public class Consume01 {
    //普通交换机
    public static final String NORMAL_EXCHANGE = "normal_echange";
    //死信交换机的名称
    public static final String DEAD_EXCHANGE = "dead_exchange";
    //普通队列名称
    public static final  String NORMAL_QUEUE = "normal_queue";
    //死信队列
    public static final String DEAD_QUEUE = "dead_queue";

    public static void main(String[] args) throws Exception {
        Channel channel = RabbitMqUtils.getChannel();
        //声明死信和普通家换季，类型为direct
        channel.exchangeDeclare(NORMAL_EXCHANGE, BuiltinExchangeType.DIRECT);
        channel.exchangeDeclare(DEAD_EXCHANGE, BuiltinExchangeType.DIRECT);
        //声明普通队列
        Map<String,Object> arguments = new HashMap<>();
        //过期时间 10000ms
        //arguments.put("x-message-tt",10000);
        //正常队列设置死信交换机
        arguments.put("x-dead-letter-exchange",DEAD_EXCHANGE);
        //设置死信 RoutingKey
        arguments.put("x-dead-letter-routing-key","lisi");
        channel.queueDeclare(NORMAL_QUEUE,false,false,false,arguments);

        ///////////////////////////////////////////////////
        //声明死信队列
        channel.queueDeclare(DEAD_QUEUE,false,false,false,null);
        //绑定普通的交换机与普通队列
        channel.queueBind(NORMAL_QUEUE,NORMAL_EXCHANGE,"zhangsan");
        //绑定死信队列的交换机与死信的队列
        channel.queueBind(DEAD_QUEUE,DEAD_EXCHANGE,"lisi");
        System.out.println("等待接收消息.....");


        DeliverCallback deliverCallback = (consumerTag,message) ->{
            System.out.println("c1接收消息:"+new String(message.getBody()));
        };
        channel.basicConsume(NORMAL_QUEUE,true,deliverCallback,comsumerTag->{});
    }
}

Product01

public class Product01 {
    //普通交换机
    public static final String NORMAL_EXCHANGE = "normal_echange";

    public static void main(String[] args) throws Exception {
        Channel channel = RabbitMqUtils.getChannel();
        //死信消息，设置TTL时间，单位是ms，10000ms
        AMQP.BasicProperties properties = new AMQP.BasicProperties().builder().expiration("10000").build();
        for(int i=1;i<11;i++){
            String message = "info"+i;
            channel.basicPublish(NORMAL_EXCHANGE,"zhangsan",properties,message.getBytes());
        }
    }
}

先启动consumer01，创建出各个队列已经交换机，在关闭c1，模拟c1无法接收消息！

后启动Product01，消息进入普通队列，无法消费、10s后进入死信队列

Consumer02

public class Consume02 {
   //死信队列
    public static final String DEAD_QUEUE = "dead_queue";

    public static void main(String[] args) throws Exception {
        Channel channel = RabbitMqUtils.getChannel();
        System.out.println("等待接收消息.....");
        DeliverCallback deliverCallback = (consumerTag,message) ->{
            System.out.println("c2接收消息:"+new String(message.getBody()));
        };
        channel.basicConsume(DEAD_QUEUE,true,deliverCallback,comsumerTag->{});
    }
}

在启动Consumer02，消费死信队列中的消息！