kafka没有重试机制不支持消息重试，也没有死信队列，因此使用kafka做消息队列时，需要自己实现消息重试的功能。

实现

创建新的kafka主题作为重试队列：

1. 创建一个topic作为重试topic，用于接收等待重试的消息。
2. 普通topic消费者设置待重试消息的下一个重试topic。
3. 从重试topic获取待重试消息储存到redis的zset中，并以下一次消费时间排序
4. 定时任务从redis获取到达消费事件的消息，并把消息发送到对应的topic
5. 同一个消息重试次数过多则不再重试

代码实现

1、新建springboot项目

4.0.0org.springframework.bootspring-boot-starter-parent2.2.8.RELEASE com.lagou.kafka.demodemo-retryqueue0.0.1-SNAPSHOTdemo-retryqueueDemo project for Spring Boot1.8org.springframework.bootspring-boot-starter-data-redisorg.springframework.bootspring-boot-starter-weborg.springframework.kafkaspring-kafkacom.alibabafastjson1.2.73org.springframework.bootspring-boot-starter-testtestorg.junit.vintagejunit-vintage-engineio.projectreactorreactor-testtestorg.springframework.kafkaspring-kafka-testtestorg.springframework.bootspring-boot-maven-plugin

2、添加application.properties

# bootstrap.servers
spring.kafka.bootstrap-servers=node1:9092
# key序列化器
spring.kafka.producer.key-serializer=org.apache.kafka.common.serialization.StringSerializer
# value序列化器
spring.kafka.producer.value-serializer=org.apache.kafka.common.serialization.StringSerializer# 消费组id：group.id
spring.kafka.consumer.group-id=retryGroup
# key反序列化器
spring.kafka.consumer.key-deserializer=org.apache.kafka.common.serialization.StringDeserializer
# value反序列化器
spring.kafka.consumer.value-deserializer=org.apache.kafka.common.serialization.StringDeserializer# redis数据库编号
spring.redis.database=0
# redis主机地址
spring.redis.host=node1
# redis端口
spring.redis.port=6379
# Redis服务器连接密码（默认为空）
spring.redis.password=
# 连接池最大连接数（使用负值表示没有限制）
spring.redis.jedis.pool.max-active=20
# 连接池最大阻塞等待时间（使用负值表示没有限制）
spring.redis.jedis.pool.max-wait=-1
# 连接池中的最大空闲连接
spring.redis.jedis.pool.max-idle=10
# 连接池中的最小空闲连接
spring.redis.jedis.pool.min-idle=0
# 连接超时时间（毫秒）
spring.redis.timeout=1000# Kafka主题名称，业务主题
spring.kafka.topics.test=tp_demo_retry_01
# 重试队列，重试主题
spring.kafka.topics.retry=tp_demo_retry_02

3、RetryqueueApplication

package com.lagou.kafka.demo;import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;@SpringBootApplication
public class RetryqueueApplication {public static void main(String[] args) {SpringApplication.run(RetryqueueApplication.class, args);}}

4、AppConfig

package com.lagou.kafka.demo.config;import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.data.redis.connection.RedisConnectionFactory;
import org.springframework.data.redis.core.RedisTemplate;@Configuration
public class AppConfig {@Beanpublic RedisTemplate redisTemplate(RedisConnectionFactory factory) {RedisTemplate template = new RedisTemplate<>();// 配置连接工厂template.setConnectionFactory(factory);return template;}}

5、RetryController

package com.lagou.kafka.demo.controller;import com.lagou.kafka.demo.service.KafkaService;
import org.apache.kafka.clients.producer.ProducerRecord;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;import java.util.concurrent.ExecutionException;@RestController
public class RetryController {@Autowiredprivate KafkaService kafkaService;@Value("${spring.kafka.topics.test}")private String topic;@RequestMapping("/send/{message}")public String sendMessage(@PathVariable String message) throws ExecutionException, InterruptedException {ProducerRecord record = new ProducerRecord<>(topic,message);// 向业务主题发送消息String result = kafkaService.sendMessage(record);return result;}}

6、KafkaService

package com.lagou.kafka.demo.service;import org.apache.kafka.clients.producer.ProducerRecord;
import org.apache.kafka.clients.producer.RecordMetadata;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.kafka.core.KafkaTemplate;
import org.springframework.kafka.support.SendResult;
import org.springframework.stereotype.Service;import java.util.concurrent.ExecutionException;@Service
public class KafkaService {private Logger log = LoggerFactory.getLogger(KafkaService.class);@Autowiredprivate KafkaTemplate kafkaTemplate;public String sendMessage(ProducerRecord record) throws ExecutionException, InterruptedException {SendResult result = this.kafkaTemplate.send(record).get();RecordMetadata metadata = result.getRecordMetadata();String returnResult = metadata.topic() + "\t" + metadata.partition() + "\t" + metadata.offset();log.info("发送消息成功：" + returnResult);return returnResult;}}

7、RetryService

package com.lagou.kafka.demo.service;import com.alibaba.fastjson.JSON;
import com.lagou.kafka.demo.entity.RetryRecord;
import org.apache.kafka.clients.consumer.ConsumerRecord;
import org.apache.kafka.common.header.Header;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.kafka.core.KafkaTemplate;
import org.springframework.stereotype.Service;import java.nio.ByteBuffer;
import java.util.Calendar;
import java.util.Date;@Service
public class RetryService {private static final Logger log = LoggerFactory.getLogger(RetryService.class);/*** 消息消费失败后下一次消费的延迟时间(秒)* 第一次重试延迟10秒;第	二次延迟30秒,第三次延迟1分钟...*/private static final int[] RETRY_INTERVAL_SECONDS = {10, 30, 1*60, 2*60, 5*60, 10*60, 30*60, 1*60*60, 2*60*60};/*** 重试topic*/@Value("${spring.kafka.topics.retry}")private String retryTopic;@Autowiredprivate KafkaTemplate kafkaTemplate;public void consumerLater(ConsumerRecord record){// 获取消息的已重试次数int retryTimes = getRetryTimes(record);Date nextConsumerTime = getNextConsumerTime(retryTimes);// 如果达到重试次数，则不再重试if(nextConsumerTime == null) {return;}// 组织消息RetryRecord retryRecord = new RetryRecord();retryRecord.setNextTime(nextConsumerTime.getTime());retryRecord.setTopic(record.topic());retryRecord.setRetryTimes(retryTimes);retryRecord.setKey(record.key());retryRecord.setValue(record.value());// 转换为字符串String value = JSON.toJSONString(retryRecord);// 发送到重试队列kafkaTemplate.send(retryTopic, null, value);}/*** 获取消息的已重试次数*/private int getRetryTimes(ConsumerRecord record){int retryTimes = -1;for(Header header : record.headers()){if(RetryRecord.KEY_RETRY_TIMES.equals(header.key())){ByteBuffer buffer = ByteBuffer.wrap(header.value());retryTimes = buffer.getInt();}}retryTimes++;return retryTimes;}/*** 获取待重试消息的下一次消费时间*/private Date getNextConsumerTime(int retryTimes){// 重试次数超过上限,不再重试if(RETRY_INTERVAL_SECONDS.length < retryTimes) {return null;}Calendar calendar = Calendar.getInstance();calendar.add(Calendar.SECOND, RETRY_INTERVAL_SECONDS[retryTimes]);return calendar.getTime();}
}

8、ConsumerListener

package com.lagou.kafka.demo.listener;import com.lagou.kafka.demo.service.RetryService;
import org.apache.kafka.clients.consumer.ConsumerRecord;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.kafka.annotation.KafkaListener;
import org.springframework.stereotype.Component;@Component
public class ConsumerListener {private static final Logger log = LoggerFactory.getLogger(ConsumerListener.class);@Autowiredprivate RetryService kafkaRetryService;private static int index = 0;@KafkaListener(topics = "${spring.kafka.topics.test}", groupId = "${spring.kafka.consumer.group-id}")public void consume(ConsumerRecord record) {try {// 业务处理log.info("消费的消息：" + record);index++;if (index % 2 == 0) {throw new Exception("该重发了");}} catch (Exception e) {log.error(e.getMessage());// 消息重试，实际上先将消息放到rediskafkaRetryService.consumerLater(record);}}}

9、RetryListener

package com.lagou.kafka.demo.listener;import com.alibaba.fastjson.JSON;
import com.lagou.kafka.demo.entity.RetryRecord;
import org.apache.kafka.clients.consumer.ConsumerRecord;
import org.apache.kafka.clients.producer.ProducerRecord;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.data.redis.core.RedisTemplate;
import org.springframework.data.redis.core.ZSetOperations;
import org.springframework.kafka.annotation.KafkaListener;
import org.springframework.kafka.core.KafkaTemplate;
import org.springframework.scheduling.annotation.EnableScheduling;
import org.springframework.scheduling.annotation.Scheduled;
import org.springframework.stereotype.Component;import java.util.Set;
import java.util.UUID;@Component
@EnableScheduling
public class RetryListener {private Logger log = LoggerFactory.getLogger(RetryListener.class);private static final String RETRY_KEY_ZSET = "_retry_key";private static final String RETRY_VALUE_MAP = "_retry_value";@Autowiredprivate RedisTemplate redisTemplate;@Autowiredprivate KafkaTemplate kafkaTemplate;@Value("${spring.kafka.topics.test}")private String bizTopic;@KafkaListener(topics = "${spring.kafka.topics.retry}")
//    public void consume(List> list) {
//        for(ConsumerRecord record : list){public void consume(ConsumerRecord record) {System.out.println("需要重试的消息：" + record);RetryRecord retryRecord = JSON.parseObject(record.value(), RetryRecord.class);/*** 防止待重试消息太多撑爆redis,可以将待重试消息按下一次重试时间分开存储放到不同介质* 例如下一次重试时间在半小时以后的消息储存到mysql,并定时从mysql读取即将重试的消息储储存到redis*/// 通过redis的zset进行时间排序String key = UUID.randomUUID().toString();redisTemplate.opsForHash().put(RETRY_VALUE_MAP, key, record.value());redisTemplate.opsForZSet().add(RETRY_KEY_ZSET, key, retryRecord.getNextTime());}
//    }/*** 定时任务从redis读取到达重试时间的消息,发送到对应的topic*/
//    @Scheduled(cron="2 * * * * *")@Scheduled(fixedDelay = 2000)public void retryFromRedis() {log.warn("retryFromRedis----begin");long currentTime = System.currentTimeMillis();// 根据时间倒序获取Set> typedTuples =redisTemplate.opsForZSet().reverseRangeByScoreWithScores(RETRY_KEY_ZSET, 0, currentTime);// 移除取出的消息redisTemplate.opsForZSet().removeRangeByScore(RETRY_KEY_ZSET, 0, currentTime);for(ZSetOperations.TypedTuple