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当消费者消费完消息之后,通常会发送一个ack应答确认信息给生产者,但是这中间有可能因为网络中断等原因,导致生产者未能收到确认消息,由此这条消息将会被 重复发送给其他消费者进行消费,实际上这条消息已经被消费过了,这就是重复消费的问题。
消息幂等性,其实就是保证同一个消息不被消费者重复消费两次。
消费者端实现幂等性,意味着消息永远不会消费多次,即使收到了多条一样的消息。通常有两种方式来避免消费重复消费:
方式1: 消息全局 ID 或者写个唯一标识(如时间戳、UUID 等) :每次消费消息之前根据消息 id 去判断该消息是否已消费过,如果已经消费过,则不处理这条消息,否则正常消费消息,并且进行入库操作。(消息全局 ID 作为数据库表的主键,防止重复)
方式2: 利用 Redis 的 setnx 命令:给消息分配一个全局 ID,消费该消息时,先去 Redis 中查询有没消费记录,无则以键值对形式写入 Redis ,有则不消费该消息。
<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>
<parent>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-parent</artifactId>
<version>2.7.0</version>
<relativePath/> <!-- lookup parent from repository -->
</parent>
<groupId>com.mq</groupId>
<artifactId>rabbitmq</artifactId>
<version>0.0.1-SNAPSHOT</version>
<name>rabbitmq</name>
<description>Demo project for Spring Boot</description>
<properties>
<java.version>1.8</java.version>
</properties>
<dependencies>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-web</artifactId>
</dependency>
<!-- https://mvnrepository.com/artifact/org.springframework.boot/spring-boot-starter-amqp -->
<!--springboot rabbit 启动器-->
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-amqp</artifactId>
<version>2.7.0</version>
</dependency>
<!-- https://mvnrepository.com/artifact/org.projectlombok/lombok -->
<dependency>
<groupId>org.projectlombok</groupId>
<artifactId>lombok</artifactId>
<version>1.18.24</version>
<scope>provided</scope>
</dependency>
<dependency>
<groupId>mysql</groupId>
<artifactId>mysql-connector-java</artifactId>
</dependency>
<!-- https://mvnrepository.com/artifact/cn.hutool/hutool-all -->
<dependency>
<groupId>cn.hutool</groupId>
<artifactId>hutool-all</artifactId>
<version>5.8.3</version>
</dependency>
<dependency>
<groupId>com.baomidou</groupId>
<artifactId>mybatis-plus-boot-starter</artifactId>
<version>3.4.0</version>
</dependency>
<dependency>
<groupId>com.baomidou</groupId>
<artifactId>mybatis-plus</artifactId>
<version>3.4.0</version>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-data-redis</artifactId>
<version>2.6.7</version>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-test</artifactId>
<scope>test</scope>
</dependency>
</dependencies>
<build>
<plugins>
<plugin>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-maven-plugin</artifactId>
</plugin>
</plugins>
</build>
</project>
spring:
application:
name: rabbitmq
rabbitmq:
host: 10.0.0.4
port: 5672
username: admin
password: admin
virtual-host: /
publisher-confirm-type: correlated # 开启消息发布确认机制
publisher-returns: true # 发布消息返回监听回调
# 指定消息确认模式
listener:
simple:
acknowledge-mode: manual
# 未正确路由的消息发送到备份队列
# 使用备份交换机模式,mandatory 将无效,即就算 mandatory设 置为 false,路由失败的消息同样会被投递到绑定的备份交换机
template:
mandatory: true
redis:
host: 10.0.0.4
database: 0
port: 6379
timeout: 300ms
datasource:
url: jdbc:mysql://10.0.0.4:3306/Test?useUnicode=true&characterEncoding=utf-8&serverTimezone=Asia/Shanghai
username: root
password: root
server:
port: 8080
# mybatis 插件打印日志,打印查询结果
mybatis-plus:
configuration:
log-impl: org.apache.ibatis.logging.stdout.StdOutImpl
CREATE TABLE `message_idempotent` (
`message_id` varchar(50) NOT NULL COMMENT '消息ID',
`message_content` varchar(2000) DEFAULT NULL COMMENT '消息内容',
PRIMARY KEY (`message_id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;
package com.mq.rabbitmq.vo;
import com.baomidou.mybatisplus.extension.activerecord.Model;
import lombok.AllArgsConstructor;
import lombok.Data;
import lombok.NoArgsConstructor;
/**
* @ClassName MessageIdempotent
* @Description TODO
* @Author 听秋
* @Date 2022/6/23 16:25
* @Version 1.0
**/
@Data
@NoArgsConstructor
@AllArgsConstructor
public class MessageIdempotent extends Model<MessageIdempotent> {
private String messageId;
private String messageContent;
}
package com.mq.rabbitmq.mapper;
import com.baomidou.mybatisplus.core.mapper.BaseMapper;
import com.mq.rabbitmq.vo.MessageIdempotent;
import org.apache.ibatis.annotations.Mapper;
/**
* @ClassName MessageIdempotentMapper
* @Description TODO
* @Author 听秋
* @Date 2022/6/23 19:03
* @Version 1.0
**/
@Mapper
public interface MessageIdempotentMapper extends BaseMapper<MessageIdempotent> {
}
package com.mq.rabbitmq.config;
import org.springframework.amqp.core.*;
import org.springframework.beans.factory.annotation.Qualifier;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import java.util.HashMap;
import java.util.Map;
/**
* @ClassName DirectConfig
* @Description TODO direct 交换机配置类
* @Author 听秋
* @Date 2022/6/17 16:30
* @Version 1.0
**/
@Configuration
public class ExchangeConfig {
/**
* 创建 direct 队列
* */
@Bean
Queue DirectQueue01() {
return new Queue("DirectQueue-01",true);
}
/**
* 创建 direct 交换机
* */
@Bean
DirectExchange DirectExchange01() {
return new DirectExchange("DirectExchange-01");
}
/**
* 绑定 direct 队列和交换机
* */
@Bean
Binding bindingDirect01() {
return BindingBuilder.bind(DirectQueue01()).to(DirectExchange01()).with("DirectRouting01");
}
}
package com.mq.rabbitmq.callback;
import org.springframework.amqp.core.ReturnedMessage;
import org.springframework.amqp.rabbit.connection.CorrelationData;
import org.springframework.amqp.rabbit.core.RabbitTemplate;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Component;
import javax.annotation.PostConstruct;
/**
* @ClassName MyConfirmCallback
* @Description TODO 自定义消息发送确认的回调
* @Author 听秋
* @Date 2022/6/21 19:12
* @Version 1.0
**/
@Component
public class MyConfirmCallback implements RabbitTemplate.ConfirmCallback, RabbitTemplate.ReturnsCallback {
@Autowired
private RabbitTemplate rabbitTemplate;
/**
* PostConstruct: 用于在依赖关系注入完成之后需要执行的方法上,以执行任何初始化
*/
@PostConstruct
public void init() {
// 指定 ConfirmCallback
rabbitTemplate.setConfirmCallback(this);
// 指定 ReturnCallback
rabbitTemplate.setReturnsCallback(this);
}
/**
* Confirmation callback.
*
* 确认消息是否成功到达交换机中,不管是否到达交换机,该回调都会执行
* 生产者 → 交换机
*/
@Override
public void confirm(CorrelationData correlationData, boolean ack, String cause) {
System.out.println("发布消息的UUID为:" + correlationData.getId());
if (ack) {
System.out.println("消息发布成功!");
} else {
System.out.println("消息发布失败!失败原因是:" + cause);
}
}
/**
* Returned message callback.
*
* 确认消息是否从交换机成功到达队列中,失败将会执行,成功则不执行
* 交换机 → 队列
*/
@Override
public void returnedMessage(ReturnedMessage returned) {
System.out.println("ReturnsCallback 回调内容:" + returned);
}
}
package com.mq.rabbitmq.controller;
import lombok.extern.slf4j.Slf4j;
import org.springframework.amqp.core.Message;
import org.springframework.amqp.core.MessageDeliveryMode;
import org.springframework.amqp.core.MessagePostProcessor;
import org.springframework.amqp.core.MessageProperties;
import org.springframework.amqp.rabbit.connection.CorrelationData;
import org.springframework.amqp.rabbit.core.RabbitTemplate;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RestController;
import java.util.UUID;
/**
* @ClassName DirectController
* @Description TODO
* @Author 听秋
* @Date 2022/6/17 16:48
* @Version 1.0
**/
@RestController
@Slf4j
public class QueueController {
@Autowired
private RabbitTemplate rabbitTemplate;
/**
* 消息幂等性
* */
@GetMapping("/sendMessage")
public void sendMessage(String msg, String routingKey, String id) {
MessageProperties messageProperties = new MessageProperties();
messageProperties.setMessageId(id);
messageProperties.setContentType("text/plain");
messageProperties.setContentEncoding("utf-8");
Message message = new Message(msg.getBytes(), messageProperties);
log.info("生产消息:" + message.toString());
// 消息发送确认回调
CorrelationData correlationData = new CorrelationData(UUID.randomUUID().toString());
rabbitTemplate.convertAndSend("DirectExchange-01", routingKey, message, correlationData);
}
}
控制台
RabbitMQ 队列
package com.mq.rabbitmq.controller;
import cn.hutool.core.util.ObjectUtil;
import com.baomidou.mybatisplus.core.conditions.query.QueryWrapper;
import com.mq.rabbitmq.vo.MessageIdempotent;
import com.rabbitmq.client.Channel;
import lombok.extern.slf4j.Slf4j;
import org.springframework.amqp.core.Message;
import org.springframework.amqp.rabbit.annotation.RabbitListener;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.data.redis.core.StringRedisTemplate;
import org.springframework.stereotype.Component;
import java.io.IOException;
import java.nio.charset.StandardCharsets;
/**
* @ClassName DirectReceiver
* @Description TODO
* @Author 听秋
* @Date 2022/6/21 10:40
* @Version 1.0
**/
@Component
@Slf4j
public class Consumer {
@Autowired
private StringRedisTemplate stringRedisTemplate;
/**
* 基于本地消息表实现消息幂等性
* @param message
*/
@RabbitListener(queues = "DirectQueue-01")
public void receiveMessage02(Message message, Channel channel) throws IOException {
String messageId = message.getMessageProperties().getMessageId();
String messageContent = new String(message.getBody(), StandardCharsets.UTF_8);
MessageIdempotent messageIdempotent = new MessageIdempotent();
QueryWrapper<MessageIdempotent> queryWrapper = new QueryWrapper<>();
queryWrapper.eq("message_id", messageId);
MessageIdempotent msg = messageIdempotent.selectOne(queryWrapper);
if (ObjectUtil.isNull(msg)) {
messageIdempotent.setMessageId(messageId);
messageIdempotent.setMessageContent(messageContent);
messageIdempotent.insert();
log.info("DirectQueue-01-消费者收到消息,消息ID:" + messageId + " 消息内容:" + messageContent);
// 消息确认
channel.basicAck(message.getMessageProperties().getDeliveryTag(), false);
} else {
log.info("消息 " + messageId + " 已经消费过!");
}
}
控制台
RabbitMQ 队列
数据库
控制台
RabbitMQ 队列
package com.mq.rabbitmq.controller;
import cn.hutool.core.util.ObjectUtil;
import com.baomidou.mybatisplus.core.conditions.query.QueryWrapper;
import com.mq.rabbitmq.vo.MessageIdempotent;
import com.rabbitmq.client.Channel;
import lombok.extern.slf4j.Slf4j;
import org.springframework.amqp.core.Message;
import org.springframework.amqp.rabbit.annotation.RabbitListener;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.data.redis.core.StringRedisTemplate;
import org.springframework.stereotype.Component;
import java.io.IOException;
import java.nio.charset.StandardCharsets;
/**
* @ClassName DirectReceiver
* @Description TODO
* @Author 听秋
* @Date 2022/6/21 10:40
* @Version 1.0
**/
@Component
@Slf4j
public class Consumer {
@Autowired
private StringRedisTemplate stringRedisTemplate;
/**
* 基于 redis 实现消息幂等性
* @param message
*/
//@RabbitHandler
//@RabbitListener(queues = "DirectQueue-01")
public void receiveMessage01(Message message, Channel channel) throws IOException {
String messageId = message.getMessageProperties().getMessageId();
String messageContent = new String(message.getBody(), StandardCharsets.UTF_8);
// 消息不存在则创建,返回 true
Boolean exist = stringRedisTemplate.opsForValue().setIfAbsent(messageId, messageContent);
if (!exist) {
log.info("消息 " + messageId + " 已经消费过");
} else {
// 消息确认
channel.basicAck(message.getMessageProperties().getDeliveryTag(), false);
log.info("DirectQueue-01-消费者收到消息,消息ID:" + messageId + " 消息内容:" + messageContent);
}
}
}
控制台
RabbitMQ 队列
Redis
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