RabbitMQ-死信队列

Posted 2022-09-05 插肩而过放个p

死信队列

死信的概念

顾名思义就是无法被消费的消息，一般来说，producer 将消息投递到 broker 或者直接到 queue 里了，consumer 从 queue 取出消息进行消费，但某些时候由于特定的原因导致 queue 中的某些消息无法被消费，这样的消息如果没有后续的处理，就变成了死信，有死信自然就有了死信队列。

死信消息来源

• 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

生产者代码

public class Producer 
    private static final String NORMAL_EXCHANGE = "normal_exchange";
    public static void main(String[] args)throws Exception 
        try(Channel channel = RabbitMqUtils.getChannel())
            channel.exchangeDeclare(NORMAL_EXCHANGE, BuiltinExchangeType.DIRECT);
            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());
                System.out.println("生产者发送信息");
            
        
    

消费者C1代码（启动后关闭模拟器接收不到消息）

public class Consumer01 
    private static final String NORMAL_EXCHANGE = "normal_exchange";
    private static final String DEAD_EXCHANGE = "dead_exchange";

    public static void main(String[] args) throws Exception 
        Channel channel = RabbitMqUtils.getChannel();
        channel.exchangeDeclare(NORMAL_EXCHANGE, BuiltinExchangeType.DIRECT);
        channel.exchangeDeclare(DEAD_EXCHANGE, BuiltinExchangeType.DIRECT);

        String deadQueue = "dead-queue";
        channel.queueDeclare(deadQueue,false,false,false,null);
        channel.queueBind(deadQueue,DEAD_EXCHANGE,"lisi");

        Map<String,Object> params = new HashMap<>();
        params.put("x-dead-letter-exchange",DEAD_EXCHANGE);
        params.put("x-dead-letter-routing-key","lisi");
        String normalQueue = "normal-queue";
        channel.queueDeclare(normalQueue,false,false,false,params);
        channel.queueBind(normalQueue,NORMAL_EXCHANGE,"zhangsan");
        System.out.println("wait...");
        DeliverCallback deliverCallback = (consumerTag,delivery) ->
            String message = new String(delivery.getBody(),"UTF-8");
            System.out.println("Consumer01接收到消息" + message);
        ;
        channel.basicConsume(normalQueue,true,deliverCallback,consumerTag -> );

    

消费者C2代码

public class Consumer02 
    private static final String DEAD_EXCHANGE = "dead_exchange";
    public static void main(String[] argv) throws Exception 
        Channel channel = RabbitMqUtils.getChannel();
        channel.exchangeDeclare(DEAD_EXCHANGE, BuiltinExchangeType.DIRECT);
        String deadQueue = "dead-queue";
        channel.queueDeclare(deadQueue, false, false, false, null);
        channel.queueBind(deadQueue, DEAD_EXCHANGE, "lisi");
        System.out.println("等待接收死信队列消息.....");
        DeliverCallback deliverCallback = (consumerTag, delivery) -> 
            String message = new String(delivery.getBody(), "UTF-8");
            System.out.println("Consumer02 接收死信队列的消息" + message);
        ;
        channel.basicConsume(deadQueue, true, deliverCallback, consumerTag -> 
        );
    

结果

此时normal-queue中有10条消息

normal-queue中消息未被消耗转入dead-queue（死信队列）

运行Consumer02接收死信队列信息

结果

队列达到最大长度

生产者

public class Producer 
    private static final String NORMAL_EXCHANGE = "normal_exchange";
    public static void main(String[] argv) throws Exception 
        try (Channel channel = RabbitMqUtils.getChannel()) 
            channel.exchangeDeclare(NORMAL_EXCHANGE, BuiltinExchangeType.DIRECT);
            //该信息是用作演示队列个数限制
            for (int i = 1; i <11 ; i++) 
                String message="info"+i;
                channel.basicPublish(NORMAL_EXCHANGE,"zhangsan",null, message.getBytes());
                System.out.println("生产者发送消息:"+message);
            
        
    

C1消费者

public class Consumer01 
    private static final String NORMAL_EXCHANGE = "normal_exchange";
    private static final String DEAD_EXCHANGE = "dead_exchange";

    public static void main(String[] args) throws Exception 
        Channel channel = RabbitMqUtils.getChannel();
        channel.exchangeDeclare(NORMAL_EXCHANGE, BuiltinExchangeType.DIRECT);
        channel.exchangeDeclare(DEAD_EXCHANGE, BuiltinExchangeType.DIRECT);

        String deadQueue = "dead-queue";
        channel.queueDeclare(deadQueue,false,false,false,null);
        channel.queueBind(deadQueue,DEAD_EXCHANGE,"lisi");

        Map<String,Object> params = new HashMap<>();
        params.put("x-dead-letter-exchange",DEAD_EXCHANGE);
        params.put("x-dead-letter-routing-key","lisi");

        params.put("x-max-length",6);

        String normalQueue = "normal-queue";
        channel.queueDeclare(normalQueue,false,false,false,params);
        channel.queueBind(normalQueue,NORMAL_EXCHANGE,"zhangsan");
        System.out.println("wait...");
        DeliverCallback deliverCallback = (consumerTag,delivery) ->
            String message = new String(delivery.getBody(),"UTF-8");
            System.out.println("Consumer01接收到消息" + message);
        ;
        channel.basicConsume(normalQueue,true,deliverCallback,consumerTag -> );

    

消息被拒

生产者
和上一个代码一样

C1消费者

public class Consumer02 
    private static final String DEAD_EXCHANGE = "dead_exchange";
    public static void main(String[] argv) throws Exception 
        Channel channel = RabbitMqUtils.getChannel();
        channel.exchangeDeclare(DEAD_EXCHANGE, BuiltinExchangeType.DIRECT);
        String deadQueue = "dead-queue";
        channel.queueDeclare(deadQueue, false, false, false, null);
        channel.queueBind(deadQueue, DEAD_EXCHANGE, "lisi");
        System.out.println("等待接收死信队列消息.....");
        DeliverCallback deliverCallback = (consumerTag, delivery) -> 
            String message = new String(delivery.getBody(), "UTF-8");
            System.out.println("Consumer02 接收死信队列的消息" + message);
        ;
        channel.basicConsume(deadQueue, true, deliverCallback, consumerTag -> 
        );
    

C2消费者
//和上一个代码一样