redis读写分离之lettuce

ゞ浴缸里的玫瑰 2022-12-20 11:16 214阅读 0赞

# 问题 #

redis使用过程中，很多情况都是读多写少，而不管是主从、哨兵、集群，从节点都只是用来备份，为了最大化节约用户成本，我们需要利用从节点来进行读，分担主节点压力，这里我们继续上一章的jedis的读写分离，由于springboot现在redis集群默认用的是lettuce，所以介绍下lettuce读写分离

# 读写分离 #

## 主从读写分离 ##

这里先建一个主从集群，1主3从，一般情况下只需要进行相关配置如下：

spring:
      redis:
        host: redisMastHost
        port: 6379
        lettuce:
          pool:
            max-active: 512
            max-idle: 256
            min-idle: 256
            max-wait: -1

这样就可以直接注入redisTemplate，读写数据了，但是这个默认只能读写主，如果需要设置readfrom，则需要自定义factory，下面给出两种方案

### 方案一（适用于非aws） ###

只需要配置主节点，从节点会信息会自动从主节点获取

@Configuration
    class WriteToMasterReadFromReplicaConfiguration {
    
      @Bean
      public LettuceConnectionFactory redisConnectionFactory() {
    
        LettuceClientConfiguration clientConfig = LettuceClientConfiguration.builder()
          .readFrom(ReadFrom.SLAVE_PREFERRED)
          .build();
    
        RedisStandaloneConfiguration serverConfig = new RedisStandaloneConfiguration("server", 6379);
    
        return new LettuceConnectionFactory(serverConfig, clientConfig);
      }
    }

### 方案二（云上redis，比如aws） ###

下面给个demo

import io.lettuce.core.ReadFrom;
    import io.lettuce.core.models.role.RedisNodeDescription;
    import org.apache.commons.lang3.StringUtils;
    import org.apache.commons.pool2.impl.GenericObjectPoolConfig;
    import org.slf4j.Logger;
    import org.slf4j.LoggerFactory;
    import org.springframework.beans.factory.annotation.Qualifier;
    import org.springframework.beans.factory.annotation.Value;
    import org.springframework.context.annotation.Bean;
    import org.springframework.context.annotation.Configuration;
    import org.springframework.data.redis.connection.RedisStaticMasterReplicaConfiguration;
    import org.springframework.data.redis.connection.lettuce.LettuceClientConfiguration;
    import org.springframework.data.redis.connection.lettuce.LettuceConnectionFactory;
    import org.springframework.data.redis.connection.lettuce.LettucePoolingClientConfiguration;
    import org.springframework.data.redis.core.RedisTemplate;
    import org.springframework.data.redis.serializer.StringRedisSerializer;
    
    import java.time.Duration;
    import java.util.List;
    import java.util.concurrent.atomic.AtomicInteger;
    import java.util.stream.Collectors;
    import java.util.stream.IntStream;
    import java.util.stream.Stream;
    
    @Configuration
    public class RedisConfig {
        @Value("${spring.redis1.master}")
        private String master;
        @Value("${spring.redis1.slaves:}")
        private String slaves;
    
        @Value("${spring.redis1.port}")
        private int port;
    
        @Value("${spring.redis1.timeout:200}")
        private long timeout;
    
        @Value("${spring.redis1.lettuce.pool.max-idle:256}")
        private int maxIdle;
    
        @Value("${spring.redis1.lettuce.pool.min-idle:256}")
        private int minIdle;
    
        @Value("${spring.redis1.lettuce.pool.max-active:512}")
        private int maxActive;
    
        @Value("${spring.redis1.lettuce.pool.max-wait:-1}")
        private long maxWait;
    
        private static Logger logger = LoggerFactory.getLogger(RedisConfig.class);
        private final AtomicInteger index = new AtomicInteger(-1);
        @Bean(value = "lettuceConnectionFactory1")
        LettuceConnectionFactory lettuceConnectionFactory1(GenericObjectPoolConfig genericObjectPoolConfig) {
            RedisStaticMasterReplicaConfiguration configuration = new RedisStaticMasterReplicaConfiguration(
                    this.master, this.port);
            if(StringUtils.isNotBlank(slaves)){
                String[] slaveHosts=slaves.split(",");
                for (int i=0;i<slaveHosts.length;i++){
                    configuration.addNode(slaveHosts[i], this.port);
                }
            }
            LettuceClientConfiguration clientConfig =
                    LettucePoolingClientConfiguration.builder().readFrom(ReadFrom.SLAVE).commandTimeout(Duration.ofMillis(timeout))
                            .poolConfig(genericObjectPoolConfig).build();
            return new LettuceConnectionFactory(configuration, clientConfig);
        }
    
        /**
         * GenericObjectPoolConfig 连接池配置
         * @return
         */
        @Bean
        public GenericObjectPoolConfig genericObjectPoolConfig() {
            GenericObjectPoolConfig genericObjectPoolConfig = new GenericObjectPoolConfig();
            genericObjectPoolConfig.setMaxIdle(maxIdle);
            genericObjectPoolConfig.setMinIdle(minIdle);
            genericObjectPoolConfig.setMaxTotal(maxActive);
            genericObjectPoolConfig.setMaxWaitMillis(maxWait);
            return genericObjectPoolConfig;
        }
    
        @Bean(name = "redisTemplate1")
        public RedisTemplate redisTemplate(@Qualifier("lettuceConnectionFactory1") LettuceConnectionFactory connectionFactory) {
            RedisTemplate<String,String> template = new RedisTemplate<String,String>();
            template.setConnectionFactory(connectionFactory);
            template.setKeySerializer(new StringRedisSerializer());
            template.setValueSerializer(new StringRedisSerializer());
            template.setHashKeySerializer(new StringRedisSerializer());
            template.setHashValueSerializer(new StringRedisSerializer());
            logger.info("redis 连接成功");
            return template;
        }
    
    
    }

这里的核心代码在readfrom的设置，lettuce提供了5中选项，分别是

*  MASTER
 *  MASTER\_PREFERRED
 *  SLAVE\_PREFERRED
 *  SLAVE
 *  NEAREST  
    最新的版本SLAVE改成了ReadFrom.REPLICA  
    这里设置为SlAVE，那么读请求都会走从节点，但是这里有个bug，每次都会读取最后一个从节点，其他从节点都不会有请求过去，跟踪源代码发现节点顺序是一定的，但是每次getConnection时每次都会获取最后一个，下面是缓存命令情况  
    ![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2xwMTk4NjExMjY_size_16_color_FFFFFF_t_70_pic_center]  
    解决方案就是自定义一个readFrom，如下

LettuceClientConfiguration clientConfig =
                    LettucePoolingClientConfiguration.builder().readFrom(new ReadFrom() {
                        @Override
                        public List<RedisNodeDescription> select(Nodes nodes) {
                            List<RedisNodeDescription> allNodes = nodes.getNodes();
                            int ind = Math.abs(index.incrementAndGet() % allNodes.size());
                            RedisNodeDescription selected = allNodes.get(ind);
                            logger.info("Selected random node {} with uri {}", ind, selected.getUri());
                            List<RedisNodeDescription> remaining = IntStream.range(0, allNodes.size())
                                    .filter(i -> i != ind)
                                    .mapToObj(allNodes::get).collect(Collectors.toList());
                            return Stream.concat(
                                    Stream.of(selected),
                                    remaining.stream()
                            ).collect(Collectors.toList());
                        }
                    }).commandTimeout(Duration.ofMillis(timeout))
                            .poolConfig(genericObjectPoolConfig).build();
            return new LettuceConnectionFactory(configuration, clientConfig);

手动实现顺序读各个从节点，修改后调用情况如下，由于还有其他应用连接该redis，所以监控图中非绝对均衡  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2xwMTk4NjExMjY_size_16_color_FFFFFF_t_70_pic_center 1]

## 哨兵模式 ##

这个我就提供一个简单demo

@Configuration
    @ComponentScan("com.redis")
    public class RedisConfig {
    
        @Bean
        public LettuceConnectionFactory redisConnectionFactory() {
    //        return new LettuceConnectionFactory(new RedisStandaloneConfiguration("192.168.80.130", 6379));
            RedisSentinelConfiguration sentinelConfig = new RedisSentinelConfiguration()
                    .master("mymaster")
                    // 哨兵地址
                    .sentinel("192.168.80.130", 26379)
                    .sentinel("192.168.80.130", 26380)
                    .sentinel("192.168.80.130", 26381);
    
            LettuceClientConfiguration clientConfig = LettuceClientConfiguration.builder().
            readFrom(ReadFrom.SLAVE_PREFERRED).build();
            return new LettuceConnectionFactory(sentinelConfig, clientConfig);
        }
    
        @Bean
        public RedisTemplate redisTemplate(RedisConnectionFactory redisConnectionFactory) {
            RedisTemplate redisTemplate = new RedisTemplate();
            redisTemplate.setConnectionFactory(redisConnectionFactory);
            // 可以配置对象的转换规则，比如使用json格式对object进行存储。
            // Object --> 序列化 --> 二进制流 --> redis-server存储
            redisTemplate.setKeySerializer(new StringRedisSerializer());
            redisTemplate.setValueSerializer(new JdkSerializationRedisSerializer());
            return redisTemplate;
        }
    
    }

## 集群模式 ##

集群模式就比较简单了，直接套用下面demo

import io.lettuce.core.ReadFrom;
    import io.lettuce.core.resource.ClientResources;
    import lombok.extern.slf4j.Slf4j;
    import org.apache.commons.lang3.StringUtils;
    import org.springframework.beans.factory.annotation.Qualifier;
    import org.springframework.beans.factory.annotation.Value;
    import org.springframework.context.annotation.Bean;
    import org.springframework.context.annotation.Configuration;
    import org.springframework.data.redis.connection.RedisClusterConfiguration;
    import org.springframework.data.redis.connection.RedisConnectionFactory;
    import org.springframework.data.redis.connection.RedisNode;
    import org.springframework.data.redis.connection.lettuce.LettuceConnectionFactory;
    import org.springframework.data.redis.connection.lettuce.LettucePoolingClientConfiguration;
    import org.springframework.data.redis.core.RedisTemplate;
    import org.springframework.data.redis.serializer.StringRedisSerializer;
    
    import java.time.Duration;
    import java.util.HashSet;
    import java.util.Set;
    
    @Slf4j
    @Configuration
    public class Redis2Config {
    
        @Value("${spring.redis2.cluster.nodes: com:9736}")
        public String REDIS_HOST;
    
        @Value("${spring.redis2.cluster.port:9736}")
        public int REDIS_PORT;
    
        @Value("${spring.redis2.cluster.type:}")
        public String REDIS_TYPE;
        @Value("${spring.redis2.cluster.read-from:master}")
        public String READ_FROM;
        @Value("${spring.redis2.cluster.max-redirects:1}")
        public int REDIS_MAX_REDIRECTS;
    
        @Value("${spring.redis2.cluster.share-native-connection:true}")
        public boolean REDIS_SHARE_NATIVE_CONNECTION;
    
        @Value("${spring.redis2.cluster.validate-connection:false}")
        public boolean VALIDATE_CONNECTION;
    
        @Value("${spring.redis2.cluster.shutdown-timeout:100}")
        public long SHUTDOWN_TIMEOUT;
    
        @Bean(value = "myRedisConnectionFactory")
        public RedisConnectionFactory connectionFactory(ClientResources clientResources) {
            RedisClusterConfiguration clusterConfiguration = new RedisClusterConfiguration();
            if (StringUtils.isNotEmpty(REDIS_HOST)) {
                String[] serverArray = REDIS_HOST.split(",");
                Set<RedisNode> nodes = new HashSet<RedisNode>();
                for (String ipPort : serverArray) {
                    String[] ipAndPort = ipPort.split(":");
                    nodes.add(new RedisNode(ipAndPort[0].trim(), Integer.valueOf(ipAndPort[1])));
                }
                clusterConfiguration.setClusterNodes(nodes);
            }
            if (REDIS_MAX_REDIRECTS > 0) {
                clusterConfiguration.setMaxRedirects(REDIS_MAX_REDIRECTS);
            }
    
            LettucePoolingClientConfiguration.LettucePoolingClientConfigurationBuilder clientConfigurationBuilder = LettucePoolingClientConfiguration.builder()
                    .clientResources(clientResources).shutdownTimeout(Duration.ofMillis(SHUTDOWN_TIMEOUT));
            if (READ_FROM.equals("slave")) {
                clientConfigurationBuilder.readFrom(ReadFrom.SLAVE_PREFERRED);
            } else if (READ_FROM.equals("nearest")) {
                clientConfigurationBuilder.readFrom(ReadFrom.NEAREST);
            } else if (READ_FROM.equals("master")) {
                clientConfigurationBuilder.readFrom(ReadFrom.MASTER_PREFERRED);
            }
            LettuceConnectionFactory lettuceConnectionFactory = new LettuceConnectionFactory(clusterConfiguration, clientConfigurationBuilder.build());
            lettuceConnectionFactory.afterPropertiesSet();
            return lettuceConnectionFactory;
        }
    
        @Bean(name = "myRedisTemplate")
        public RedisTemplate myRedisTemplate(@Qualifier("myRedisConnectionFactory") RedisConnectionFactory connectionFactory) {
            RedisTemplate template = new RedisTemplate();
            template.setConnectionFactory(connectionFactory);
            template.setKeySerializer(new StringRedisSerializer());
            template.setValueSerializer(new StringRedisSerializer());
            return template;
        }
    
    
    }

不过这里集群模式不推荐读取从节点，因为在生产中有可能导致某一分片挂掉以至于整个集群都不可用，可以考虑从节点整多个，然后配置读写分离。

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