springboot整合Redis的Lettuce连接池连接超时：io.lettuce.core.RedisCommandTimeoutException: Command timed out

一、可能最大连接数/超时时间设置过小

如图，检查最大连接数和超时时间，将其调大。

redis:
    lettuce:
      pool:
        MaxTotal: 50 #最大连接数
        minIdle: 1
        maxWaitMillis: 5000
        maxIdle: 5
        testOnBorrow: true
        testOnReturn: true
        testWhileIdle: true
    redis-a:
      database: 8
      hostName: 127.0.0.1
      port: 6379
      timeout: 5000 #超时时间
    redis-b:
      database: 8
      hostName: 172.16.35.60
      port: 31105
      password: tenxcloud
      timeout: 5000 #超时时间

二、链接池中出现断链接

产生这种问题的原因有如下两点：
1、Lettuce 自适应拓扑刷新（Adaptive updates）与定时拓扑刷新（Periodic updates） 是默认关闭的。
2、项目用了k8s做docker容器化部署，但是k8s有设置空闲连接超时就断开，所以当你从连接池拿到被断开的连接时就会报错。

解决方案都是一致的：

方案一：每次链接都进行自动校验（亲测好用）

说明：lettuce提供了校验连接的方法，lettuce提供了校验连接的方法 只是默认没开启
开启的话是每次获取连接都会校验，开启获取连接的校验。

@Component
@Slf4j
public class LettuceConnectionValidConfig implements InitializingBean {
    @Autowired
    private RedisConnectionFactory redisConnectionFactory;
 
    @Override
    public void afterPropertiesSet() throws Exception {
        if(redisConnectionFactory instanceof LettuceConnectionFactory){
            LettuceConnectionFactory c=(LettuceConnectionFactory)redisConnectionFactory;
            c.setValidateConnection(true);
        }
    }
}

方案二：定时任务

说明：每隔2秒校验异常lettuce连接是否正常，解决长期空闲lettuce连接关闭但是netty不能及时监控到的问题。

@Component
@Slf4j
public class LettuceConnectionValidTask   {
    @Autowired
    private RedisConnectionFactory redisConnectionFactory;
 
    @Scheduled(cron="0/2 * * * * ?")
    public void task() {
        if(redisConnectionFactory instanceof LettuceConnectionFactory){
            LettuceConnectionFactory c=(LettuceConnectionFactory)redisConnectionFactory;
            c.validateConnection();
        }
    }
}

方案三：springboot2.3以上版本，可添加配置解决。

# 解决redis 240秒超时问题
    lettuce:
      cluster:
        refresh:
          adaptive: true
          period: 20

方案四：排除lettuce，采用jedis。

		<dependency>
			<groupId>org.springframework.boot</groupId>
			<artifactId>spring-boot-starter-data-redis</artifactId>
			<exclusions>
				<exclusion>
					<groupId>io.lettuce</groupId>
					<artifactId>lettuce-core</artifactId>
				</exclusion>
			</exclusions>
		</dependency>
		
		<dependency>
			<groupId>redis.clients</groupId>
			<artifactId>jedis</artifactId>
		</dependency>

注意配置文件把lettuce.pool换成jedis.pool。

方案五：重写连接工厂实例（极度不推荐）。

说明：重写连接工厂实例，更改其LettuceClientConfiguration 为开启拓扑更新。

@Configuration
public class RedisConfig {


    @Autowired
    private RedisProperties redisProperties;

    //这是固定的模板
    //自己定义了一个RedisTemplate
    @Bean
    @SuppressWarnings("all")
    public RedisTemplate<String, Object> redisTemplate(@Qualifier("lettuceConnectionFactoryUvPv") RedisConnectionFactory factory) {
        RedisTemplate<String, Object> template = new RedisTemplate<>();
        template.setConnectionFactory(factory);

        //Json序列化配置
        Jackson2JsonRedisSerializer<Object> jackson2JsonRedisSerializer = new Jackson2JsonRedisSerializer<Object>(Object.class);
        ObjectMapper om = new ObjectMapper();
        om.setVisibility(PropertyAccessor.ALL, JsonAutoDetect.Visibility.ANY);
        om.activateDefaultTyping(om.getPolymorphicTypeValidator());
        om.enableDefaultTyping(ObjectMapper.DefaultTyping.NON_FINAL);
        //解决序列化问题
        om.configure(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES, false);
        jackson2JsonRedisSerializer.setObjectMapper(om);

        //String的序列化
        StringRedisSerializer stringRedisSerializer = new StringRedisSerializer();

        //key采用String的序列化方式
        template.setKeySerializer(stringRedisSerializer);
        //hash的key也采用String的序列化方式
        template.setHashKeySerializer(stringRedisSerializer);

        //value序列化方式采用jackson
        template.setValueSerializer(jackson2JsonRedisSerializer);

        //hash的value序列化方式采用jackson
        template.setHashValueSerializer(jackson2JsonRedisSerializer);
        template.afterPropertiesSet();

        return template;
    }

    /**
     * 为RedisTemplate配置Redis连接工厂实现
     * LettuceConnectionFactory实现了RedisConnectionFactory接口
     * UVPV用Redis
     *
     * @return 返回LettuceConnectionFactory
     */
    @Bean(destroyMethod = "destroy")
    //这里要注意的是，在构建LettuceConnectionFactory 时，如果不使用内置的destroyMethod，可能会导致Redis连接早于其它Bean被销毁
    public LettuceConnectionFactory lettuceConnectionFactoryUvPv() throws Exception {

        List<String> clusterNodes = redisProperties.getCluster().getNodes();
        Set<RedisNode> nodes = new HashSet<>();
        clusterNodes.forEach(address -> nodes.add(new RedisNode(address.split(":")[0].trim(), Integer.parseInt(address.split(":")[1]))));
        RedisClusterConfiguration clusterConfiguration = new RedisClusterConfiguration();
        clusterConfiguration.setClusterNodes(nodes);
        clusterConfiguration.setPassword(RedisPassword.of(redisProperties.getPassword()));
        clusterConfiguration.setMaxRedirects(redisProperties.getCluster().getMaxRedirects());


        RedisStandaloneConfiguration  redisStandaloneConfiguration=new RedisStandaloneConfiguration();
        redisStandaloneConfiguration.setHostName(redisProperties.getHost());
        redisStandaloneConfiguration.setPassword(redisProperties.getPassword());
        redisStandaloneConfiguration.setDatabase(redisProperties.getDatabase());
        redisStandaloneConfiguration.setPort(redisProperties.getPort());

        GenericObjectPoolConfig poolConfig = new GenericObjectPoolConfig();
        poolConfig.setMaxIdle(redisProperties.getLettuce().getPool().getMaxIdle());
        poolConfig.setMinIdle(redisProperties.getLettuce().getPool().getMinIdle());
        poolConfig.setMaxTotal(redisProperties.getLettuce().getPool().getMaxActive());

        return new LettuceConnectionFactory(redisStandaloneConfiguration, getLettuceClientConfiguration(poolConfig));
    }

    /**
     * 配置LettuceClientConfiguration 包括线程池配置和安全项配置
     *
     * @param genericObjectPoolConfig common-pool2线程池
     * @return lettuceClientConfiguration
     */
    private LettuceClientConfiguration getLettuceClientConfiguration(GenericObjectPoolConfig genericObjectPoolConfig) {
        /*
        ClusterTopologyRefreshOptions配置用于开启自适应刷新和定时刷新。如自适应刷新不开启，Redis集群变更时将会导致连接异常！
         */
        ClusterTopologyRefreshOptions topologyRefreshOptions = ClusterTopologyRefreshOptions.builder()
                //开启自适应刷新
                //.enableAdaptiveRefreshTrigger(ClusterTopologyRefreshOptions.RefreshTrigger.MOVED_REDIRECT, ClusterTopologyRefreshOptions.RefreshTrigger.PERSISTENT_RECONNECTS)
                //开启所有自适应刷新，MOVED，ASK，PERSISTENT都会触发
                .enableAllAdaptiveRefreshTriggers()
                // 自适应刷新超时时间(默认30秒)
                .adaptiveRefreshTriggersTimeout(Duration.ofSeconds(25)) //默认关闭开启后时间为30秒
                // 开周期刷新
                .enablePeriodicRefresh(Duration.ofSeconds(20))  // 默认关闭开启后时间为60秒 ClusterTopologyRefreshOptions.DEFAULT_REFRESH_PERIOD 60  .enablePeriodicRefresh(Duration.ofSeconds(2)) = .enablePeriodicRefresh().refreshPeriod(Duration.ofSeconds(2))
                .build();
        return LettucePoolingClientConfiguration.builder()
                .poolConfig(genericObjectPoolConfig)
                .clientOptions(ClusterClientOptions.builder().topologyRefreshOptions(topologyRefreshOptions).build())
                //将appID传入连接，方便Redis监控中查看
                //.clientName(appName + "_lettuce")
                .build();
    }

}