introduce

Dead letter queue: the queue in which messages are not consumed in time and messages are not consumed in time has the following reasons:
1. A message is rejected (basic.reject/ basic.nack) and request = false
2. The queue reaches the maximum length
3. Message TTL expired

scene

1. Enter the initial queue in hours, wait for 30 minutes, and then enter the 5-minute queue
2. The message enters the execution queue after waiting for 5 minutes
3. Return to the 5-minute queue after execution failure
4. After 5 failures, the message enters the 2-hour queue
5. Messages wait for 2 hours to enter the execution queue
6. After 5 failures, discard the message or do other processing

Use

• Install MQ

Use docker mode to install, select the version with management

docker pull rabbitmq:management
docker run -d -p 5672:5672 -p 15672:15672 --name rabbitmq rabbitmq:management

Visit localhost: 15672, default account password guest/guest

• Project configuration

(1) create a springboot project
(2) configure mq connection information in the application.properties configuration file

spring.rabbitmq.host=localhost
spring.rabbitmq.port=5672
spring.rabbitmq.username=guest
spring.rabbitmq.password=guest

(3) queue configuration

package com.df.ps.mq;

import org.springframework.amqp.core.Binding;
import org.springframework.amqp.core.BindingBuilder;
import org.springframework.amqp.core.Queue;
import org.springframework.amqp.core.TopicExchange;
import org.springframework.amqp.rabbit.connection.ConnectionFactory;
import org.springframework.amqp.rabbit.listener.SimpleMessageListenerContainer;
import org.springframework.amqp.rabbit.listener.adapter.MessageListenerAdapter;
import org.springframework.beans.factory.annotation.Autowire;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;

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

@Configuration
public class MqConfig {

    //time
    @Value("${spring.df.buffered.min:120}")
    private int springdfBufferedTime;

    @Value("${spring.df.high-buffered.min:5}")
    private int springdfHighBufferedTime;

    @Value("${spring.df.low-buffered.min:120}")
    private int springdfLowBufferedTime;

    // 30min Buffered Queue
    @Value("${spring.df.queue:spring-df-buffered-queue}")
    private String springdfBufferedQueue;

    @Value("${spring.df.topic:spring-df-buffered-topic}")
    private String springdfBufferedTopic;

    @Value("${spring.df.route:spring-df-buffered-route}")
    private String springdfBufferedRouteKey;

    // 5M Buffered Queue
    @Value("${spring.df.high-buffered.queue:spring-df-high-buffered-queue}")
    private String springdfHighBufferedQueue;

    @Value("${spring.df.high-buffered.topic:spring-df-high-buffered-topic}")
    private String springdfHighBufferedTopic;

    @Value("${spring.df.high-buffered.route:spring-df-high-buffered-route}")
    private String springdfHighBufferedRouteKey;

    // High Queue
    @Value("${spring.df.high.queue:spring-df-high-queue}")
    private String springdfHighQueue;

    @Value("${spring.df.high.topic:spring-df-high-topic}")
    private String springdfHighTopic;

    @Value("${spring.df.high.route:spring-df-high-route}")
    private String springdfHighRouteKey;

    // 2H Low Buffered Queue
    @Value("${spring.df.low-buffered.queue:spring-df-low-buffered-queue}")
    private String springdfLowBufferedQueue;

    @Value("${spring.df.low-buffered.topic:spring-df-low-buffered-topic}")
    private String springdfLowBufferedTopic;

    @Value("${spring.df.low-buffered.route:spring-df-low-buffered-route}")
    private String springdfLowBufferedRouteKey;

    // Low Queue
    @Value("${spring.df.low.queue:spring-df-low-queue}")
    private String springdfLowQueue;

    @Value("${spring.df.low.topic:spring-df-low-topic}")
    private String springdfLowTopic;

    @Value("${spring.df.low.route:spring-df-low-route}")
    private String springdfLowRouteKey;


    @Bean(autowire = Autowire.BY_NAME, value = "springdfBufferedQueue")
    Queue springdfBufferedQueue() {
        int bufferedTime = 1000 * 60 * springdfBufferedTime;
        return createBufferedQueue(springdfBufferedQueue, springdfHighBufferedTopic, springdfHighBufferedRouteKey, bufferedTime);
    }

    @Bean(autowire = Autowire.BY_NAME, value = "springdfHighBufferedQueue")
    Queue springdfHighBufferedQueue() {
        int highBufferedTime = 1000 * 60 * springdfHighBufferedTime;
        return createBufferedQueue(springdfHighBufferedQueue, springdfHighTopic, springdfHighRouteKey, highBufferedTime);
    }

    @Bean(autowire = Autowire.BY_NAME, value = "springdfHighQueue")
    Queue springdfHighQueue() {
        return new Queue(springdfHighQueue, true);
    }

    @Bean(autowire = Autowire.BY_NAME, value = "springdfLowBufferedQueue")
    Queue springdfLowBufferedQueue() {
        int lowBufferedTime = 1000 * 60 * springdfLowBufferedTime;
        return createBufferedQueue(springdfLowBufferedQueue, springdfLowTopic, springdfLowRouteKey, lowBufferedTime);
    }

    @Bean(autowire = Autowire.BY_NAME, value = "springdfLowQueue")
    Queue springdfLowQueue() {
        return new Queue(springdfLowQueue, true);
    }


    @Bean(autowire = Autowire.BY_NAME, value = "springdfBufferedTopic")
    TopicExchange springdfBufferedTopic() {
        return new TopicExchange(springdfBufferedTopic);
    }

    @Bean
    Binding springBuffereddf(Queue springdfBufferedQueue, TopicExchange springdfBufferedTopic) {
        return BindingBuilder.bind(springdfBufferedQueue).to(springdfBufferedTopic).with(springdfBufferedRouteKey);
    }


    @Bean(autowire = Autowire.BY_NAME, value = "springdfHighBufferedTopic")
    TopicExchange springdfHighBufferedTopic() {
        return new TopicExchange(springdfHighBufferedTopic);
    }

    @Bean
    Binding springHighBuffereddf(Queue springdfHighBufferedQueue, TopicExchange springdfHighBufferedTopic) {
        return BindingBuilder.bind(springdfHighBufferedQueue).to(springdfHighBufferedTopic).with(springdfHighBufferedRouteKey);
    }

    @Bean(autowire = Autowire.BY_NAME, value = "springdfHighTopic")
    TopicExchange springdfHighTopic() {
        return new TopicExchange(springdfHighTopic);
    }

    @Bean
    Binding springHighdf(Queue springdfHighQueue, TopicExchange springdfHighTopic) {
        return BindingBuilder.bind(springdfHighQueue).to(springdfHighTopic).with(springdfHighRouteKey);
    }

    @Bean(autowire = Autowire.BY_NAME, value = "springdfLowBufferedTopic")
    TopicExchange springdfLowBufferedTopic() {
        return new TopicExchange(springdfLowBufferedTopic);
    }

    @Bean
    Binding springLowBuffereddf(Queue springdfLowBufferedQueue, TopicExchange springdfLowBufferedTopic) {
        return BindingBuilder.bind(springdfLowBufferedQueue).to(springdfLowBufferedTopic).with(springdfLowBufferedRouteKey);
    }

    @Bean(autowire = Autowire.BY_NAME, value = "springdfLowTopic")
    TopicExchange springdfLowTopic() {
        return new TopicExchange(springdfLowTopic);
    }

    @Bean
    Binding springLowdf(Queue springdfLowQueue, TopicExchange springdfLowTopic) {
        return BindingBuilder.bind(springdfLowQueue).to(springdfLowTopic).with(springdfLowRouteKey);
    }


    @Bean
    SimpleMessageListenerContainer container(ConnectionFactory connectionFactory,
                                             MessageListenerAdapter listenerAdapter) {
        SimpleMessageListenerContainer container = new SimpleMessageListenerContainer();
        container.setConnectionFactory(connectionFactory);
        container.setQueueNames(springdfHighQueue, springdfLowQueue);
        container.setMessageListener(listenerAdapter);
        return container;
    }

    @Bean
    MessageListenerAdapter listenerAdapter(IntegrationReceiver receiver) {


        MessageListenerAdapter adapter = new MessageListenerAdapter(receiver);
        adapter.setDefaultListenerMethod("receive");
        Map<String, String> queueOrTagToMethodName = new HashMap<>();
        queueOrTagToMethodName.put(springdfHighQueue, "springdfHighReceive");
        queueOrTagToMethodName.put(springdfLowQueue, "springdfLowReceive");
        adapter.setQueueOrTagToMethodName(queueOrTagToMethodName);
        return adapter;

    }


    private Queue createBufferedQueue(String queueName, String topic, String routeKey, int bufferedTime) {
        Map<String, Object> args = new HashMap<>();
        args.put("x-dead-letter-exchange", topic);
        args.put("x-dead-letter-routing-key", routeKey);
        args.put("x-message-ttl", bufferedTime);
        // Persistence or not
        boolean durable = true;
        // Private queues that can only be used by the creator and are automatically deleted after disconnection
        boolean exclusive = false;
        // Whether to delete the queue automatically after all consumer clients are disconnected
        boolean autoDelete = false;

        return new Queue(queueName, durable, exclusive, autoDelete, args);
    }
}

• Consumer configuration

package com.df.ps.mq;

import com.fasterxml.jackson.databind.ObjectMapper;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.amqp.rabbit.core.RabbitTemplate;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Value;

import java.util.Map;

public class MqReceiver {

    private static Logger logger = LoggerFactory.getLogger(MqReceiver.class);

    @Value("${high-retry:5}")
    private int highRetry;

    @Value("${low-retry:5}")
    private int lowRetry;

    @Value("${spring.df.high-buffered.topic:spring-df-high-buffered-topic}")
    private String springdfHighBufferedTopic;

    @Value("${spring.df.high-buffered.route:spring-df-high-buffered-route}")
    private String springdfHighBufferedRouteKey;

    @Value("${spring.df.low-buffered.topic:spring-df-low-buffered-topic}")
    private String springdfLowBufferedTopic;

    @Value("${spring.df.low-buffered.route:spring-df-low-buffered-route}")
    private String springdfLowBufferedRouteKey;

    private final RabbitTemplate rabbitTemplate;
    @Autowired
    public MqReceiver(RabbitTemplate rabbitTemplate) {
        this.rabbitTemplate = rabbitTemplate;
    }

    public void receive(Object message) {
        if (logger.isInfoEnabled()) {
            logger.info("default receiver: " + message);
        }
    }

    /**
     * Messages enter the 5-minute cache queue from the initial queue
     * @param message
     */
    public void highReceiver(Object message){
        ObjectMapper mapper = new ObjectMapper();
        Map msg = mapper.convertValue(message, Map.class);

        try{
            logger.info("Do message processing here...");
        }catch (Exception e){
            int times = msg.get("times") == null ? 0 : (int) msg.get("times");
            if (times < highRetry) {
                msg.put("times", times + 1);
                rabbitTemplate.convertAndSend(springdfHighBufferedTopic,springdfHighBufferedRouteKey,message);
            } else {
                msg.put("times", 0);
                rabbitTemplate.convertAndSend(springdfLowBufferedTopic,springdfLowBufferedRouteKey,message);
            }
        }
    }

    /**
     * Message enters 2-hour buffer queue from 5-minute buffer queue
     * @param message
     */
    public void lowReceiver(Object message){
        ObjectMapper mapper = new ObjectMapper();
        Map msg = mapper.convertValue(message, Map.class);
        
        try {
            logger.info("Do message processing here...");
        }catch (Exception e){
            int times = msg.get("times") == null ? 0 : (int) msg.get("times");
            if (times < lowRetry) {
                rabbitTemplate.convertAndSend(springdfLowBufferedTopic,springdfLowBufferedRouteKey,message);
            }else{
                logger.info("Message cannot be consumed...");
            }
        } 
    }
}