Connecting to Redis on Lettuce (Java)

This section describes how to access a Redis instance on Lettuce. For more information about how to use other Redis clients, visit the Redis official website.

Spring Data Redis is already integrated with Jedis and Lettuce for Spring Boot projects. In addition, Spring Boot 1.x is integrated with Jedis, and Spring Boot 2.x with Lettuce. Therefore, you do not need to import Lettuce in Spring Boot 2.x and later projects.

Prerequisites

A DCS Redis instance has been created and is in the Running state.
View the IP address and port number of the DCS Redis instance to be accessed.
For details, see Viewing Details of a DCS Instance.

Pom Configuration

<!-- Enable Spring Data Redis, Lettuce-supported SDK is integrated by default -->
<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-data-redis</artifactId>
</dependency>

application.properties Configuration

Single-node, master/standby, and Proxy Cluster

#Redis host
spring.redis.host=<host>
#Redis port
spring.redis.port=<port>
#Redis database number
spring.redis.database=0
#Redis password
spring.redis.password=<password>
#Redis read/write timeout
spring.redis.timeout=2000

Redis Cluster

#Redis Cluster node information
spring.redis.cluster.nodes=<ip:port>,<ip:port>,<ip:port>
#Redis Cluster max redirecting times
spring.redis.cluster.max-redirects=3
#Redis Cluster node password
spring.redis.password=<password>
#Redis Cluster timeout
spring.redis.timeout=2000
#Enable adaptive topology refresh
spring.redis.lettuce.cluster.refresh.adaptive=true
#Enable topology refresh every 10 seconds
spring.redis.lettuce.cluster.refresh.period=10S

Bean Configuration

Single-node, master/standby, and Proxy Cluster

import java.time.Duration;

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.RedisConnectionFactory;
import org.springframework.data.redis.connection.RedisStandaloneConfiguration;
import org.springframework.data.redis.connection.lettuce.LettuceClientConfiguration;
import org.springframework.data.redis.connection.lettuce.LettuceConnectionFactory;

import io.lettuce.core.ClientOptions;
import io.lettuce.core.SocketOptions;

/**
* Lettuce non-pooling configuration (use either this or the application.properties configuration)
*/
@Configuration
public class RedisConfiguration {

    @Value("${redis.host}")
    private String redisHost;

    @Value("${redis.port:6379}")
    private Integer redisPort = 6379;

    @Value("${redis.database:0}")
    private Integer redisDatabase = 0;

    @Value("${redis.password:}")
    private String redisPassword;

    @Value("${redis.connect.timeout:2000}")
    private Integer redisConnectTimeout = 2000;

    @Value("${redis.read.timeout:2000}")
    private Integer redisReadTimeout = 2000;

    @Bean
    public RedisConnectionFactory redisConnectionFactory(LettuceClientConfiguration clientConfiguration) {

        RedisStandaloneConfiguration standaloneConfiguration = new RedisStandaloneConfiguration();
        standaloneConfiguration.setHostName(redisHost);
        standaloneConfiguration.setPort(redisPort);
        standaloneConfiguration.setDatabase(redisDatabase);
        standaloneConfiguration.setPassword(redisPassword);

        LettuceConnectionFactory connectionFactory = new LettuceConnectionFactory(standaloneConfiguration, clientConfiguration);
        connectionFactory.setDatabase(redisDatabase);
        return connectionFactory;
    }

    @Bean
    public LettuceClientConfiguration clientConfiguration() {

        SocketOptions socketOptions = SocketOptions.builder().connectTimeout(Duration.ofMillis(redisConnectTimeout)).build();

        ClientOptions clientOptions = ClientOptions.builder()
                .autoReconnect(true)
                .pingBeforeActivateConnection(true)
                .cancelCommandsOnReconnectFailure(false)
                .disconnectedBehavior(ClientOptions.DisconnectedBehavior.ACCEPT_COMMANDS)
                .socketOptions(socketOptions)
                .build();

        LettuceClientConfiguration clientConfiguration = LettuceClientConfiguration.builder()
                .commandTimeout(Duration.ofMillis(redisReadTimeout))
                .clientOptions(clientOptions)
                .build();
        return clientConfiguration;
    }
}

Pooling configuration for single-node, master/standby, and Proxy Cluster instances

Enable the pooling component

<dependency>
    <groupId>org.apache.commons</groupId>
    <artifactId>commons-pool2</artifactId>
    <version>2.11.1</version>
</dependency>

Code

import java.time.Duration;

import org.apache.commons.pool2.impl.GenericObjectPoolConfig;
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.RedisConnectionFactory;
import org.springframework.data.redis.connection.RedisStandaloneConfiguration;
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 io.lettuce.core.ClientOptions;
import io.lettuce.core.SocketOptions;

/**
* Lettuce pooling configuration
*/
@Configuration
public class RedisPoolConfiguration {
    @Value("${redis.host}")
    private String redisHost;

    @Value("${redis.port:6379}")
    private Integer redisPort = 6379;

    @Value("${redis.database:0}")
    private Integer redisDatabase = 0;

    @Value("${redis.password:}")
    private String redisPassword;

    @Value("${redis.connect.timeout:2000}")
    private Integer redisConnectTimeout = 2000;

    @Value("${redis.read.timeout:2000}")
    private Integer redisReadTimeout = 2000;

    @Value("${redis.pool.minSize:50}")
    private Integer redisPoolMinSize = 50;

    @Value("${redis.pool.maxSize:200}")
    private Integer redisPoolMaxSize = 200;

    @Value("${redis.pool.maxWaitMillis:2000}")
    private Integer redisPoolMaxWaitMillis = 2000;

    @Value("${redis.pool.softMinEvictableIdleTimeMillis:1800000}")
    private Integer redisPoolSoftMinEvictableIdleTimeMillis = 30 * 60 * 1000;

    @Value("${redis.pool.timeBetweenEvictionRunsMillis:60000}")
    private Integer redisPoolBetweenEvictionRunsMillis = 60 * 1000;

    @Bean
    public RedisConnectionFactory redisConnectionFactory(LettuceClientConfiguration clientConfiguration) {

        RedisStandaloneConfiguration standaloneConfiguration = new RedisStandaloneConfiguration();
        standaloneConfiguration.setHostName(redisHost);
        standaloneConfiguration.setPort(redisPort);
        standaloneConfiguration.setDatabase(redisDatabase);
        standaloneConfiguration.setPassword(redisPassword);

        LettuceConnectionFactory connectionFactory = new LettuceConnectionFactory(standaloneConfiguration, clientConfiguration);
        connectionFactory.setDatabase(redisDatabase);
        //Disable sharing native connection before enabling pooling
        connectionFactory.setShareNativeConnection(false);
        return connectionFactory;
    }

    @Bean
    public LettuceClientConfiguration clientConfiguration() {

        SocketOptions socketOptions = SocketOptions.builder().connectTimeout(Duration.ofMillis(redisConnectTimeout)).build();

        ClientOptions clientOptions = ClientOptions.builder()
                .autoReconnect(true)
                .pingBeforeActivateConnection(true)
                .cancelCommandsOnReconnectFailure(false)
                .disconnectedBehavior(ClientOptions.DisconnectedBehavior.ACCEPT_COMMANDS)
                .socketOptions(socketOptions)
                .build();

        LettucePoolingClientConfiguration poolingClientConfiguration = LettucePoolingClientConfiguration.builder()
                .poolConfig(redisPoolConfig())
                .commandTimeout(Duration.ofMillis(redisReadTimeout))
                .clientOptions(clientOptions)
                .build();
        return poolingClientConfiguration;
    }

    private GenericObjectPoolConfig redisPoolConfig() {
        GenericObjectPoolConfig poolConfig = new GenericObjectPoolConfig();
        //Minimum idle connections in the pool
        poolConfig.setMinIdle(redisPoolMinSize);
        //Maximum idle connections in the pool
        poolConfig.setMaxIdle(redisPoolMaxSize);
        //Maximum total connections in the pool
        poolConfig.setMaxTotal(redisPoolMaxSize);
        //Wait when pool is exhausted? Set to true to wait. To validate setMaxWait, it has to be true.
        poolConfig.setBlockWhenExhausted(true);
        //Max allowed time to wait for connection after pool is exhausted. The default value -1 indicates to wait indefinitely.
        poolConfig.setMaxWait(Duration.ofMillis(redisPoolMaxWaitMillis));
        //Set to true to enable connectivity test on creating connections. Default: false.
        poolConfig.setTestOnCreate(false);
        //Set to true to enable connectivity test on borrowing connections. Default: false. Set to false for heavy-traffic services to reduce overhead.
        poolConfig.setTestOnBorrow(true);
        //Set to true to enable connectivity test on returning connections. Default: false. Set to false for heavy-traffic services to reduce overhead.
        poolConfig.setTestOnReturn(false);
        //Indicates whether to check for idle connections. If this is set to false, idle connections are not evicted.
        poolConfig.setTestWhileIdle(true);
        //Idle duration after which a connection is evicted. If the actual duration is greater than this value and the maximum number of idle connections is reached, idle connections are directly evicted.
        poolConfig.setSoftMinEvictableIdleTime(Duration.ofMillis(redisPoolSoftMinEvictableIdleTimeMillis));
        //Disable eviction policy MinEvictableIdleTimeMillis().
        poolConfig.setMinEvictableIdleTime(Duration.ofMillis(-1));
        //Interval for checking and evicting idle connections. Default: 60s.
        poolConfig.setTimeBetweenEvictionRuns(Duration.ofMillis(redisPoolBetweenEvictionRunsMillis));
        return poolConfig;
    }
}

Configuration for Redis Cluster instances

import java.time.Duration;
import java.util.ArrayList;
import java.util.List;

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.LettuceClientConfiguration;
import org.springframework.data.redis.connection.lettuce.LettuceConnectionFactory;

import io.lettuce.core.ClientOptions;
import io.lettuce.core.SocketOptions;
import io.lettuce.core.cluster.ClusterClientOptions;
import io.lettuce.core.cluster.ClusterTopologyRefreshOptions;

/**
* Lettuce Cluster non-pooling configuration (use either this or the application.properties configuration)
*/
@Configuration
public class RedisConfiguration {

    @Value("${redis.cluster.nodes}")
    private String redisClusterNodes;

    @Value("${redis.cluster.maxDirects:3}")
    private Integer redisClusterMaxDirects;

    @Value("${redis.password:}")
    private String redisPassword;

    @Value("${redis.connect.timeout:2000}")
    private Integer redisConnectTimeout = 2000;

    @Value("${redis.read.timeout:2000}")
    private Integer redisReadTimeout = 2000;

    @Value("${redis.cluster.topology.refresh.period.millis:10000}")
    private Integer redisClusterTopologyRefreshPeriodMillis = 10000;

    @Bean
    public RedisConnectionFactory redisConnectionFactory(LettuceClientConfiguration clientConfiguration) {

        RedisClusterConfiguration clusterConfiguration = new RedisClusterConfiguration();

        List<RedisNode> clusterNodes = new ArrayList<>();
        for (String clusterNodeStr : redisClusterNodes.split(",")) {
            String[] nodeInfo = clusterNodeStr.split(":");
            clusterNodes.add(new RedisNode(nodeInfo[0], Integer.valueOf(nodeInfo[1])));
        }
        clusterConfiguration.setClusterNodes(clusterNodes);

        clusterConfiguration.setPassword(redisPassword);
        clusterConfiguration.setMaxRedirects(redisClusterMaxDirects);

        LettuceConnectionFactory connectionFactory = new LettuceConnectionFactory(clusterConfiguration, clientConfiguration);
        return connectionFactory;
    }

    @Bean
    public LettuceClientConfiguration clientConfiguration() {

        SocketOptions socketOptions = SocketOptions.builder().connectTimeout(Duration.ofMillis(redisConnectTimeout)).build();

        ClusterTopologyRefreshOptions topologyRefreshOptions = ClusterTopologyRefreshOptions.builder()
                .enableAllAdaptiveRefreshTriggers()
                .enablePeriodicRefresh(Duration.ofMillis(redisClusterTopologyRefreshPeriodMillis))
                .build();

        ClusterClientOptions clientOptions = ClusterClientOptions.builder()
                .autoReconnect(true)
                .pingBeforeActivateConnection(true)
                .cancelCommandsOnReconnectFailure(false)
                .disconnectedBehavior(ClientOptions.DisconnectedBehavior.ACCEPT_COMMANDS)
                .socketOptions(socketOptions)
                .topologyRefreshOptions(topologyRefreshOptions)
                .build();

        LettuceClientConfiguration clientConfiguration = LettuceClientConfiguration.builder()
                .commandTimeout(Duration.ofMillis(redisReadTimeout))
                .clientOptions(clientOptions)
                .build();
        return clientConfiguration;
    }
}

Pooling configuration for Redis Cluster instances

Enable the pooling component

<dependency>
    <groupId>org.apache.commons</groupId>
    <artifactId>commons-pool2</artifactId>
    <version>2.11.1</version>
</dependency>

Code

import java.time.Duration;
import java.util.ArrayList;
import java.util.List;

import org.apache.commons.pool2.impl.GenericObjectPoolConfig;
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.LettuceClientConfiguration;
import org.springframework.data.redis.connection.lettuce.LettuceConnectionFactory;
import org.springframework.data.redis.connection.lettuce.LettucePoolingClientConfiguration;

import io.lettuce.core.ClientOptions;
import io.lettuce.core.SocketOptions;
import io.lettuce.core.cluster.ClusterClientOptions;
import io.lettuce.core.cluster.ClusterTopologyRefreshOptions;

/**
* Lettuce pooling configuration
*/
@Configuration
public class RedisPoolConfiguration {

    @Value("${redis.cluster.nodes}")
    private String redisClusterNodes;

    @Value("${redis.cluster.maxDirects:3}")
    private Integer redisClusterMaxDirects;

    @Value("${redis.password:}")
    private String redisPassword;

    @Value("${redis.connect.timeout:2000}")
    private Integer redisConnectTimeout = 2000;

    @Value("${redis.read.timeout:2000}")
    private Integer redisReadTimeout = 2000;

    @Value("${redis.cluster.topology.refresh.period.millis:10000}")
    private Integer redisClusterTopologyRefreshPeriodMillis = 10000;

    @Value("${redis.pool.minSize:50}")
    private Integer redisPoolMinSize = 50;

    @Value("${redis.pool.maxSize:200}")
    private Integer redisPoolMaxSize = 200;

    @Value("${redis.pool.maxWaitMillis:2000}")
    private Integer redisPoolMaxWaitMillis = 2000;

    @Value("${redis.pool.softMinEvictableIdleTimeMillis:1800000}")
    private Integer redisPoolSoftMinEvictableIdleTimeMillis = 30 * 60 * 1000;

    @Value("${redis.pool.timeBetweenEvictionRunsMillis:60000}")
    private Integer redisPoolBetweenEvictionRunsMillis = 60 * 1000;

    @Bean
    public RedisConnectionFactory redisConnectionFactory(LettuceClientConfiguration clientConfiguration) {

        RedisClusterConfiguration clusterConfiguration = new RedisClusterConfiguration();

        List<RedisNode> clusterNodes = new ArrayList<>();
        for (String clusterNodeStr : redisClusterNodes.split(",")) {
            String[] nodeInfo = clusterNodeStr.split(":");
            clusterNodes.add(new RedisNode(nodeInfo[0], Integer.valueOf(nodeInfo[1])));
        }
        clusterConfiguration.setClusterNodes(clusterNodes);

        clusterConfiguration.setPassword(redisPassword);
        clusterConfiguration.setMaxRedirects(redisClusterMaxDirects);

        LettuceConnectionFactory connectionFactory = new LettuceConnectionFactory(clusterConfiguration, clientConfiguration);
        //Disable native connection sharing before validating connection pool
        connectionFactory.setShareNativeConnection(false);
        return connectionFactory;
    }

    @Bean
    public LettuceClientConfiguration clientConfiguration() {

        SocketOptions socketOptions = SocketOptions.builder().connectTimeout(Duration.ofMillis(redisConnectTimeout)).build();

        ClusterTopologyRefreshOptions topologyRefreshOptions = ClusterTopologyRefreshOptions.builder()
                .enableAllAdaptiveRefreshTriggers()
                .enablePeriodicRefresh(Duration.ofMillis(redisClusterTopologyRefreshPeriodMillis))
                .build();

        ClusterClientOptions clientOptions = ClusterClientOptions.builder()
                .autoReconnect(true)
                .pingBeforeActivateConnection(true)
                .cancelCommandsOnReconnectFailure(false)
                .disconnectedBehavior(ClientOptions.DisconnectedBehavior.ACCEPT_COMMANDS)
                .socketOptions(socketOptions)
                .topologyRefreshOptions(topologyRefreshOptions)
                .build();

        LettucePoolingClientConfiguration clientConfiguration = LettucePoolingClientConfiguration.builder()
                .poolConfig(poolConfig())
                .commandTimeout(Duration.ofMillis(redisReadTimeout))
                .clientOptions(clientOptions)
                .build();
        return clientConfiguration;
    }

    private GenericObjectPoolConfig poolConfig() {
        GenericObjectPoolConfig poolConfig = new GenericObjectPoolConfig();
        //Minimum connections in the pool
        poolConfig.setMinIdle(redisPoolMinSize);
        //Maximum idle connections in the pool
        poolConfig.setMaxIdle(redisPoolMaxSize);
        //Maximum total connections in the pool
        poolConfig.setMaxTotal(redisPoolMaxSize);
        //Wait when pool is exhausted? Set to true to wait. To validate setMaxWait, it has to be true.
        poolConfig.setBlockWhenExhausted(true);
        //Max allowed time to wait for connection after pool is exhausted. The default value -1 indicates to wait indefinitely.
        poolConfig.setMaxWait(Duration.ofMillis(redisPoolMaxWaitMillis));
        //Set to true to enable connectivity test on creating connections. Default: false.
        poolConfig.setTestOnCreate(false);
        //Set to true to enable connectivity test on borrowing connections. Default: false. Set to false for heavy-traffic services to reduce overhead.
        poolConfig.setTestOnBorrow(true);
        //Set to true to enable connectivity test on returning connections. Default: false. Set to false for heavy-traffic services to reduce overhead.
        poolConfig.setTestOnReturn(false);
        //Indicates whether to check for idle connections. If this is set to false, idle connections are not evicted.
        poolConfig.setTestWhileIdle(true);
        //Disable connection closure when the minimum idle time is reached.
        poolConfig.setMinEvictableIdleTime(Duration.ofMillis(-1));
        //Idle duration before a connection being evicted. If the actual duration is greater than this value and the maximum number of idle connections is reached, idle connections are directly evicted. MinEvictableIdleTimeMillis (default eviction policy) is no longer used.
        poolConfig.setSoftMinEvictableIdleTime(Duration.ofMillis(redisPoolSoftMinEvictableIdleTimeMillis));
        //Interval for checking and evicting idle connections. Default: 60s.
        poolConfig.setTimeBetweenEvictionRuns(Duration.ofMillis(redisPoolBetweenEvictionRunsMillis));

        return poolConfig;
    }

}

(Optional) Configuring SSL Connections

If SSL is enabled for an instance, to access it using SSL connections, use the following content to replace the LettuceClientConfiguration construction method clientConfiguration() in Bean Configuration. For details about whether your DCS Redis instances support SSL, see Transmitting DCS Redis Data with Encryption Using SSL.

Single-node, master/standby, and Proxy Cluster

@Bean
public LettuceClientConfiguration clientConfiguration() {

    SocketOptions socketOptions = SocketOptions.builder().connectTimeout(Duration.ofMillis(redisConnectTimeout)).build();

    SslOptions sslOptions = SslOptions.builder()
        .trustManager(new File(certificationPath))
        .build();

    ClientOptions clientOptions = ClientOptions.builder()
        .sslOptions(sslOptions)
        .autoReconnect(true)
        .pingBeforeActivateConnection(true)
        .cancelCommandsOnReconnectFailure(false)
        .disconnectedBehavior(ClientOptions.DisconnectedBehavior.ACCEPT_COMMANDS)
        .socketOptions(socketOptions)
        .build();

    LettuceClientConfiguration clientConfiguration = LettuceClientConfiguration.builder()
        .commandTimeout(Duration.ofMillis(redisReadTimeout))
        .clientOptions(clientOptions)
        .useSsl()
        .build();

    return clientConfiguration;
}

Redis Cluster

@Bean
public LettuceClientConfiguration clientConfiguration() {

    SocketOptions socketOptions = SocketOptions.builder().connectTimeout(Duration.ofMillis(redisConnectTimeout)).build();

    SslOptions sslOptions = SslOptions.builder()
        .trustManager(new File(certificationPath))
        .build();

    ClusterTopologyRefreshOptions topologyRefreshOptions = ClusterTopologyRefreshOptions.builder()
        .enableAllAdaptiveRefreshTriggers()
        .enablePeriodicRefresh(Duration.ofMillis(redisClusterTopologyRefreshPeriodMillis))
        .build();

    ClusterClientOptions clientOptions = ClusterClientOptions.builder()
        .sslOptions(sslOptions)
        .autoReconnect(true)
        .pingBeforeActivateConnection(true)
        .cancelCommandsOnReconnectFailure(false)
        .disconnectedBehavior(ClientOptions.DisconnectedBehavior.ACCEPT_COMMANDS)
        .socketOptions(socketOptions)
        .topologyRefreshOptions(topologyRefreshOptions)
        .build();

    LettuceClientConfiguration clientConfiguration = LettuceClientConfiguration.builder()
        .commandTimeout(Duration.ofMillis(redisReadTimeout))
        .clientOptions(clientOptions)
        .useSsl()
        .build();

    return clientConfiguration;
}

Parameter Description

**Table 1** LettuceConnectionFactory parameters
Parameter	Type	Default Value	Description
configuration	RedisConfiguration	-	Redis connection configuration. Two subsclasses: RedisStandaloneConfiguration RedisClusterConfiguration
clientConfiguration	LettuceClientConfiguration	-	Client configuration parameter. Common subclass: LettucePoolingClientConfiguration
shareNativeConnection	boolean	true	Indicates whether to share native connections. Set to true to share. Set to false to enable connection pooling.

**Table 2** RedisStandaloneConfiguration parameters
Parameter	Default Value	Description
hostName	localhost	IP address for connecting to a DCS Redis instance
port	6379	Port number
database	0	Database subscript
password	-	Password

**Table 3** RedisClusterConfiguration parameters
Parameter	Description
clusterNodes	Cluster node connection information, including the node IP address and port number
maxRedirects	Maximum redirecting times. Recommended value: 3.
password	Password

**Table 4** LettuceClientConfiguration parameters
Parameter	Type	Default Value	Description
timeout	Duration	60s	Command timeout: Recommended: 2s.
clientOptions	ClientOptions	-	Configuration options.

**Table 5** LettucePoolingClientConfiguration parameters
Parameter	Type	Default Value	Description
timeout	Duration	60s	Command timeout: Recommended: 2s.
clientOptions	ClientOptions	-	Configuration options.
poolConfig	GenericObjectPoolConfig	-	Connection pool configuration.

**Table 6** ClientOptions parameters
Parameter	Type	Default Value	Description
autoReconnect	boolean	true	Indicates whether to automatically reconnect after disconnection. Recommended: true.
pingBeforeActivateConnection	boolean	true	Indicates whether to test connectivity on established connections. Recommended: true.
cancelCommandsOnReconnectFailure	boolean	true	Indicates whether to cancel commands after a failed reconnection attempt. Recommended: false.
disconnectedBehavior	DisconnectedBehavior	DisconnectedBehavior.DEFAULT	Indicates what to do when a connection drops. Recommended: ACCEPT_COMMANDS. DEFAULT: When autoReconnect is set true, commands are allowed to wait in queue. When autoReconnect is set to false, commands are not allowed to wait in queue. ACCEPT_COMMANDS: Allow commands to wait in queue. REJECT_COMMANDS: Do not allow commands to wait in queue.
socketOptions	SocketOptions	-	Socket configuration.

**Table 7** SocketOptions parameters
Parameter	Default Value	Description
connectTimeout	10s	Connection timeout. Recommended: 2s.

**Table 8** GenericObjectPoolConfig parameters
Parameter	Default Value	Description
minIdle	-	Minimum connections in the pool.
maxIdle	-	Maximum idle connections in the connection pool.
maxTotal	-	Maximum total connections in the connection pool.
blockWhenExhausted	true	Indicates whether to wait after the connection pool is exhausted. true: Wait. false: Do not wait. To validate maxWaitMillis, this parameter must be set to true.
maxWaitMillis	-1	Maximum amount of time a connection allocation should block before throwing an exception when the pool is exhausted. The default value –1 indicates to wait indefinitely.
testOnCreate	false	Set to true to enable connectivity test on creating connections. Default: false.
testOnBorrow	false	Set to true to enable connectivity test on borrowing connections. Default: false. Set to false for heavy-traffic services to reduce overhead.
testOnReturn	false	Set to true to enable connectivity test on returning connections. Default: false. Set to false for heavy-traffic services to reduce overhead.
testWhileIdle	false	Indicates whether to check for idle connections. If this parameter is set to false, idle connections are not evicted. Recommended value: true.
softMinEvictableIdleTimeMillis	1800000	Duration after which idle connections are evicted. If the idle duration is greater than this value and the maximum number of idle connections is reached, idle connections are directly evicted.
minEvictableIdleTimeMillis	60000	An eviction policy, set to –1 (suggested) to disable it. Use softminEvictableIdleTimeMillis instead.
timeBetweenEvictionRunsMillis	60000	Eviction interval, in milliseconds.

Suggestion for Configuring DCS Instances

Pooling connection
Different from Jedis's BIO, the bottom layer of Lettuce communicates with Redis Server based on Netty's NIO. Combining persistent connections and queues, Lettuce sends and receives multiple requests and responses spontaneously with sequential sending and receiving features of TCP. A single connection supports 3000 to 5000 QPS, but you are not advised to allow more than 3000 QPS in production systems. Pooling is not supported by Lettuce, and is disabled by default in Spring Boot. To enable pooling, validate the commons-pool2 dependency and disable native connection sharing.

By default, each Lettuce connection needs two thread pools, I/O thread pool and computation thread pool, to support I/O event reading and asynchronous event processing. If you configure connection pooling, each connection creates two thread pools, consuming high memory resources. Lettuce is strong at processing single connections based on its bottom-layer implementation, so you are not advised to use Lettuce with pooling.

Topology refresh

When connecting to a Redis Cluster instance, Lettuce randomly sends cluster nodes to the node list during initialization to obtain the distribution of cluster slots. Cluster topology structure changes when the cluster capacity is increased or decreased or a master/standby switchover occurs. Lettuce does not detect such changes by default. You can enable detection with the following configurations:

application.properties configuration

#Enable adaptive topology refresh.
spring.redis.lettuce.cluster.refresh.adaptive=true
#Enable topology refresh every 10 seconds.
spring.redis.lettuce.cluster.refresh.period=10S

API configuration

ClusterTopologyRefreshOptions topologyRefreshOptions = ClusterTopologyRefreshOptions.builder()
    .enableAllAdaptiveRefreshTriggers()
    .enablePeriodicRefresh(Duration.ofMillis(redisClusterTopologyRefreshPeriodMillis))
    .build();

ClusterClientOptions clientOptions = ClusterClientOptions.builder()
        ...
        ...
        .topologyRefreshOptions(topologyRefreshOptions)
        .build();

Blast radius
The bottom layer of Lettuce uses a combination of single persistent connection and request queue. Once network jitter or intermittent disconnection occurs or connection times out, all requests are affected. Especially when connection times out, an attempt is made to resend TCP pockets until timeout and connection drops. Requests do not recover until connections are reestablished. Requests accumulate during resending attempts. If upper-layer services time out in batches, or the resending timeout is too long in some OSs' kernels, the service system remains unavailable for a long time. Therefore, you are advised to use Jedis instead of Lettuce.