2.8 重试队列

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

<?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>2.2.8.RELEASE</version>
        <relativePath/>
        <!-- lookup parent from repository -->
    </parent>
    <groupId>com.lagou.kafka.demo</groupId>
    <artifactId>demo-retryqueue</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <name>demo-retryqueue</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>
        <dependency>
            <groupId>org.springframework.kafka</groupId>
            <artifactId>spring-kafka</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
            <exclusions>
                <exclusion>
                    <groupId>org.junit.vintage</groupId>
                    <artifactId>junit-vintage-engine</artifactId>
                </exclusion>
            </exclusions>
        </dependency>
        <dependency>
            <groupId>org.springframework.kafka</groupId>
            <artifactId>spring-kafka-test</artifactId>
            <scope>test</scope>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-data-redis</artifactId>
        </dependency>
        <dependency>
            <groupId>com.alibaba</groupId>
            <artifactId>fastjson</artifactId>
            <version>1.2.73</version>
        </dependency>
    </dependencies>
    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>
        </plugins>
    </build>
</project>

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
spring.kafka.topics.test=tp_demo_retry_01
# 重试队列
spring.kafka.topics.retry=tp_demo_retry_02

3. RetryqueueApplication.java

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.java

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
{
    @Bean
    public RedisTemplate < String, Object > redisTemplate(RedisConnectionFactory factory)
    {
        RedisTemplate < String, Object > template = new RedisTemplate < > ();
        // 配置连接工厂
        template.setConnectionFactory(factory);
        return template;
    }
}

5. KafkaController.java

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 KafkaController
{
    @Autowired
    private KafkaService kafkaService;
    @Value("${spring.kafka.topics.test}")
    private String topic;
    @RequestMapping("/send/{message}")
    public String sendMessage(@PathVariable String message) throws ExecutionException, InterruptedException
    {
        ProducerRecord < String, String > record = new ProducerRecord < > (topic, message);
        String result = kafkaService.sendMessage(record);
        return result;
    }
}

6. KafkaService.java

package com.lagou.kafka.demo.service;
import org.apache.kafka.clients.producer.ProducerRecord;
import org.apache.kafka.clients.producer.RecordMetadata;
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
{
    @Autowired
    private KafkaTemplate < String, String > kafkaTemplate;
    public String sendMessage(ProducerRecord < String, String > record) throws ExecutionException, InterruptedException
    {
        SendResult < String, String > result = this.kafkaTemplate.send(record).get();
        RecordMetadata metadata = result.getRecordMetadata();
        String returnResult = metadata.topic() + "\t" + metadata.partition() + "\t" + metadata.offset();
        System.out.println("发送消息成功：" + returnResult);
        return returnResult;
    }
}

7. ConsumerListener.java

package com.lagou.kafka.demo.listener;
import com.lagou.kafka.demo.service.KafkaRetryService;
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);
    @Autowired
    private KafkaRetryService kafkaRetryService;
    private static int index = 0;
    @KafkaListener(topics = "${spring.kafka.topics.test}", groupId = "${spring.kafka.consumer.group-id}")
    public void consume(ConsumerRecord < String, String > 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
            kafkaRetryService.consumerLater(record);
        }
    }
}

8. KafkaRetryService.java

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 KafkaRetryService
{
    private static final Logger log = LoggerFactory.getLogger(KafkaRetryService.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;
    @Autowired
    private KafkaTemplate < String, String > kafkaTemplate;
    public void consumerLater(ConsumerRecord < String, String > 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();
    }
}

9. RetryListener.java

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";
    @Autowired
    private RedisTemplate < String, Object > redisTemplate;
    @Autowired
    private KafkaTemplate < String, String > kafkaTemplate;
    @Value("${spring.kafka.topics.test}")
    private String bizTopic;
    @KafkaListener(topics = "${spring.kafka.topics.retry}")
    // public void consume(List<ConsumerRecord<String, String>> list){
    // for(ConsumerRecord<String, String> record : list){
    public void consume(ConsumerRecord < String, String > 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 < ZSetOperations.TypedTuple < Object >> 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 < Object > tuple: typedTuples)
        {
            String key = tuple.getValue().toString();
            String value = redisTemplate.opsForHash().get(RETRY_VALUE_MAP, key).toString();
            redisTemplate.opsForHash().delete(RETRY_VALUE_MAP, key);
            RetryRecord retryRecord = JSON.parseObject(value, RetryRecord.class);
            ProducerRecord record = retryRecord.parse();
            ProducerRecord recordReal = new ProducerRecord(bizTopic, record.partition(), record.timestamp(), record.key(), record.value(), record.headers());
            kafkaTemplate.send(recordReal);
        }
        // todo 发生异常将发送失败的消息重新发送到redis
    }
}

10. RetryRecord.java

package com.lagou.kafka.demo.entity;
import org.apache.kafka.clients.producer.ProducerRecord;
import org.apache.kafka.common.header.Header;
import org.apache.kafka.common.header.internals.RecordHeader;
import java.nio.ByteBuffer;
import java.util.ArrayList;
import java.util.List;
public class RetryRecord
{
    public static final String KEY_RETRY_TIMES = "retryTimes";
    private String key;
    private String value;
    private Integer retryTimes;
    private String topic;
    private Long nextTime;
    public RetryRecord()
    {}
    public String getKey()
    {
        return key;
    }
    public void setKey(String key)
    {
        this.key = key;
    }
    public String getValue()
    {
        return value;
    }
    public void setValue(String value)
    {
        this.value = value;
    }
    public Integer getRetryTimes()
    {
        return retryTimes;
    }
    public void setRetryTimes(Integer retryTimes)
    {
        this.retryTimes = retryTimes;
    }
    public String getTopic()
    {
        return topic;
    }
    public void setTopic(String topic)
    {
        this.topic = topic;
    }
    public Long getNextTime()
    {
        return nextTime;
    }
    public void setNextTime(Long nextTime)
    {
        this.nextTime = nextTime;
    }
    public ProducerRecord parse()
    {
        Integer partition = null;
        Long timestamp = System.currentTimeMillis();
        List < Header > headers = new ArrayList < > ();
        ByteBuffer retryTimesBuffer = ByteBuffer.allocate(4);
        retryTimesBuffer.putInt(retryTimes);
        retryTimesBuffer.flip();
        headers.add(new RecordHeader(RetryRecord.KEY_RETRY_TIMES, retryTimesBuffer));
        ProducerRecord sendRecord = new ProducerRecord(topic, partition, timestamp, key, value, headers);
        return sendRecord;
    }
}