[SpringBoot] Integrate RabbitMQ dead letter queue/dead letter switch

Producer side

Directory Structure

import dependencies

Modify yml

Business logic

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        DLX (Dead Letter Exchange) dead letter exchange. When a message becomes Dead Message, it can be resent to another exchange. This switch is a dead letter switch. There are two main problems here: the first is how to judge the message as a dead letter message, and the second is how the message is passed from the queue to the dead letter switch.

• Three situations in which a message becomes a dead letter message

  • Queue message length reached limit

  • The consumer rejects the message (basicNack() or basicReject) and does not put the message back into the queue (the third parameter of the basicNack() method)

  • Message TTL expired This is what I demonstrate below

• Queue bound dead letter exchange

  • Set parameters for the queue: x-dead-letter-exchange and x-dead-letter-routing-key

Producer side

Directory Structure

import dependencies

<dependencies>
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter</artifactId>
    </dependency>

    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-test</artifactId>
        <scope>test</scope>
    </dependency>

    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-amqp</artifactId>
        <version>2.5.0</version>
    </dependency>
    <dependency>
        <groupId>junit</groupId>
        <artifactId>junit</artifactId>
        <version>4.12</version>
        <scope>test</scope>
    </dependency>
</dependencies>

Modify yml

spring:
  rabbitmq:
    host: localhost
    port: 5672
    username: guest
    password: guest
    publisher-returns: true # 开启退回回调
    #三个类型：none默认不开启确认回调 correlated开启确认回调
    #simple也会确认回调 还会调用waitForConfirms()方法或waitForConfirmsOrDie()方法
    publisher-confirm-type: correlated # 开启确认回调

Business logic

/**
 * 定义交换机与队列的Bean 并且使之绑定
 * 生产者 -> 普通交换机 -> 普通队列 -> 消费者1
 *                        |
 *                        -> 死信交换机 -> 死信队列 -> 消费者2
 * 需要两个交换机两个队列、三个路由键。两个普通之间我用了"test.#" 
 * 普通与死信之间用了"test.dead.heHe" 两个死信之间用了"test.dead.#" 生产的消息用的就是"test.dead.heHe"
 */
@Component
public class RabbitMQConfig {

    public static final String EXCHANGE_NAME = "test_exchange_name";
    public static final String QUEUE_NAME = "test_queue_name";
    public static final String DEAD_EXCHANGE_NAME = "dead_exchange_name";
    public static final String DEAD_QUEUE_NAME = "dead_queue_name";

    @Bean("testExchange")
    public Exchange testExchange(){
        return ExchangeBuilder.topicExchange(EXCHANGE_NAME).durable(true).build();
    }

    @Bean("deadExchange")
    public Exchange deadExchange(){
        return ExchangeBuilder.topicExchange(DEAD_EXCHANGE_NAME).durable(true).build();
    }

    //普通队列绑定死信交换机并且带上路由键 为了实现死信消息于是配置队列TTL
    @Bean("testQueue")
    public Queue testQueue(){
        return QueueBuilder.durable(QUEUE_NAME).ttl(5000).deadLetterExchange(DEAD_EXCHANGE_NAME)
                .deadLetterRoutingKey("test.dead.heHe").build();
    }

    @Bean("deadQueue")
    public Queue deadQueue(){
        return QueueBuilder.durable(DEAD_QUEUE_NAME).build();
    }

    @Bean
    public Binding link(@Qualifier("testExchange") Exchange exchange,
                        @Qualifier("testQueue") Queue queue){
        return BindingBuilder.bind(queue).to(exchange).with("test.#").noargs();
    }

    @Bean
    public Binding deadLink(@Qualifier("deadExchange") Exchange exchange,
                            @Qualifier("deadQueue") Queue queue){
        return BindingBuilder.bind(queue).to(exchange).with("test.dead.#").noargs();
    }
}

@SpringBootTest
@RunWith(SpringRunner.class)
class RabbitmqProducerApplicationTests {

    @Autowired
    private RabbitTemplate rabbitTemplate;

    @Test
    void testProducer() {
        rabbitTemplate.setConfirmCallback(new RabbitTemplate.ConfirmCallback() {
            @Override
            public void confirm(CorrelationData correlationData, boolean b, String s) {
                if(b) System.out.println("交换机成功接受到了消息");
                else System.out.println("消息失败原因" + s);
            }
        });
        // 设置交换机处理失败消息的模式
        // true:消息到达不了队列时 会将消息重新返回给生产者 false:消息到达不了队列直接丢弃
        rabbitTemplate.setMandatory(true);
        rabbitTemplate.setReturnCallback(new RabbitTemplate.ReturnCallback() {
            @Override
            public void returnedMessage(Message message, int i, String s, String s1, String s2) {
                System.out.println("队列接受不到交换机的消息进行了失败回调");
            }
        });
        for(int i = 0; i < 10; ++i){
            rabbitTemplate.convertAndSend(RabbitMQConfig.EXCHANGE_NAME,"test.dead.heHe","HelloWorld");
        }
    }
}