Configuring Spring Data Redis with Lettuce for ElastiCache Master/Slave

Question

I have a Elasticache setup with one master and two slaves. I am still not sure how to pass in a list of master slave RedisURIs to construct a StatefulRedisMasterSlaveConnection for LettuceConnectionFactory. I only see support for standaloneConfiguration with single host and port.

LettuceClientConfiguration configuration = LettuceTestClientConfiguration.builder().readFrom(ReadFrom.SLAVE).build();
LettuceConnectionFactory factory = new LettuceConnectionFactory(SettingsUtils.standaloneConfiguration(),configuration);

I know there is a similar question Configuring Spring Data Redis with Lettuce for Redis master/slave

But I don't think it works for ElastiCache Master/Slave setup as currently the above code would try to use MasterSlaveTopologyProvider to discover slave ips. However, slave IP addresses are not reachable. So what's the right way to configure Spring Data Redis to make it compatible with Master/Slave ElastiCache? It seems to me LettuceConnectionFactory needs to take in a list of endpoints and use StaticMasterSlaveTopologyProvider in order to work.

score 6 · Answer 1 · edited Aug 01 '19 at 18:33

There have been further improvements in AWS and Lettuce making it easier to support Master/Slave.

One improvement that has happened recently in AWS is it has launched reader endpoints for Redis which distributes load among replicas: Amazon ElastiCache launches reader endpoints for Redis.

Hence the best way to connect to Redis using Spring Data Redis will be to use the primary endpoint (master) and reader endpoint (for replicas) of the Redis cluster.

You can get both of them from the AWS console. Here is a sample code:

@Bean
public LettuceConnectionFactory redisConnectionFactory() {
    LettuceClientConfiguration clientConfig = LettuceClientConfiguration.builder()
            .readFrom(ReadFrom.SLAVE_PREFERRED)
            .build();
    RedisStaticMasterReplicaConfiguration redisStaticMasterReplicaConfiguration =
            new 
     RedisStaticMasterReplicaConfiguration(REDIS_CLUSTER_PRIMARY_ENDPOINT, redisPort);
    redisStaticMasterReplicaConfiguration.addNode(REDIS_CLUSTER_READER_ENDPOINT, redisPort);
    redisStaticMasterReplicaConfiguration.setPassword(redisPassword);
    return new LettuceConnectionFactory(redisStaticMasterReplicaConfiguration, clientConfig);
}

score 0 · Accepted Answer · answered Jan 27 '18 at 13:50

Right now, static Master/Slave with provided endpoints is not supported by Spring Data Redis. I filed a ticket to add support for that.

You can implement this functionality yourself by subclassing LettuceConnectionFactory, creating an own configuration and LettuceConnectionFactory.

You would start with something like:

public static class MyLettuceConnectionFactory extends LettuceConnectionFactory {

    private final MyMasterSlaveConfiguration configuration;

    public MyLettuceConnectionFactory(MyMasterSlaveConfiguration standaloneConfig,
            LettuceClientConfiguration clientConfig) {
        super(standaloneConfig, clientConfig);
        this.configuration = standaloneConfig;
    }

    @Override
    protected LettuceConnectionProvider doCreateConnectionProvider(AbstractRedisClient client, RedisCodec<?, ?> codec) {
        return new ElasticacheConnectionProvider((RedisClient) client, codec, getClientConfiguration().getReadFrom(),
                this.configuration);
    }
}

static class MyMasterSlaveConfiguration extends RedisStandaloneConfiguration {

    private final List<RedisURI> endpoints;

    public MyMasterSlaveConfiguration(List<RedisURI> endpoints) {
        this.endpoints = endpoints;
    }

    public List<RedisURI> getEndpoints() {
        return endpoints;
    }
}

You can find all code in this gist, not posting all code here as it would be a wall of code.

Thank you so much for your prompt reply! I will give it a try. — HLiu, Jan 27 '18 at 19:17
The provided code works for ssl disabled cluster. Starting from redis 3.2.6, ElastiCache supports ssl. I already tried Redisson. It worked without any problem. So I am wondering if Lettuce already supports ssl enabled Master/Slave ElastiCache as well or plans to support it soon. — HLiu, Jan 30 '18 at 01:23
Thanks again! I applied the code change from the PR and it's working now. — HLiu, Jan 31 '18 at 07:37

Configuring Spring Data Redis with Lettuce for ElastiCache Master/Slave

2 Answers2