Spring Boot app cannot connect to Redis Replica in Docker - spring-boot

Question

I am experiencing a weird issue with Redis connectivity in the Docker.
I have a simple Spring Boot application with a Master-Replica configuration.
As well as docker-compose config which I use to start Redis Master and Redis Replica.
If I start Redis via docker-compose and Spring Boot app as a simple java process outside of Docker, everything works fine. It can successfully connect to both Master and Replica via localhost.
If I launch Spring Boot app as a Docker container alongside Redis containers it can successfully connect to Master, but not Replica. Which means that I can write and read to Master node but when I try to read from Replica I get the following error:
redis-sample-app_1 | Caused by: io.netty.channel.AbstractChannel$AnnotatedConnectException: Connection refused: redis-replica-a/172.31.0.2:7001
redis-sample-app_1 | Caused by: java.net.ConnectException: Connection refused
redis-sample-app_1 | at sun.nio.ch.SocketChannelImpl.checkConnect(Native Method) ~[na:1.8.0_302]
In the redis.conf I've changed the following to bind it to all network interfaces:
bind * -::*
protected-mode no
docker-compose.yml
version: "3"
services:
redis-master:
image: redis:alpine
command: redis-server --include /usr/local/etc/redis/redis.conf
volumes:
- ./conf/redis-master.conf:/usr/local/etc/redis/redis.conf
ports:
- "6379:6379"
redis-replica-a:
image: redis:alpine
command: redis-server --include /usr/local/etc/redis/redis.conf
volumes:
- ./conf/redis-replica.conf:/usr/local/etc/redis/redis.conf
ports:
- "7001:6379"
redis-sample-app:
image: docker.io/library/redis-sample:0.0.1-SNAPSHOT
environment:
- SPRING_REDIS_HOST=redis-master
- SPRING_REDIS_PORT=6379
- SPRING_REDIS_REPLICAS=redis-replica-a:7001
ports:
- "9080:8080"
depends_on:
- redis-master
- redis-replica-a
application.yml
spring:
redis:
port: 6379
host: localhost
replicas: localhost:7001
RedisConfig.java
#Configuration
class RedisConfig {
private static final Logger LOG = LoggerFactory.getLogger(RedisConfig.class);
#Value("${spring.redis.replicas:}")
private String replicasProperty;
private final RedisProperties redisProperties;
public RedisConfig(RedisProperties redisProperties) {
this.redisProperties = redisProperties;
}
#Bean
public StringRedisTemplate masterReplicaRedisTemplate(LettuceConnectionFactory connectionFactory) {
return new StringRedisTemplate(connectionFactory);
}
#Bean
public LettuceConnectionFactory masterReplicaLettuceConnectionFactory(LettuceClientConfiguration lettuceConfig) {
LOG.info("Master: {}:{}", redisProperties.getHost(), redisProperties.getPort());
LOG.info("Replica property: {}", replicasProperty);
RedisStaticMasterReplicaConfiguration configuration = new RedisStaticMasterReplicaConfiguration(redisProperties.getHost(), redisProperties.getPort());
if (StringUtils.hasText(replicasProperty)) {
List<RedisURI> replicas = Arrays.stream(this.replicasProperty.split(",")).map(this::toRedisURI).collect(Collectors.toList());
LOG.info("Replica nodes: {}", replicas);
replicas.forEach(replica -> configuration.addNode(replica.getHost(), replica.getPort()));
}
return new LettuceConnectionFactory(configuration, lettuceConfig);
}
#Scope("prototype")
#Bean(destroyMethod = "shutdown")
ClientResources clientResources() {
return DefaultClientResources.create();
}
#Scope("prototype")
#Bean
LettuceClientConfiguration lettuceConfig(ClientResources dcr) {
ClientOptions options = ClientOptions.builder()
.timeoutOptions(TimeoutOptions.builder().fixedTimeout(Duration.of(5, ChronoUnit.SECONDS)).build())
.disconnectedBehavior(ClientOptions.DisconnectedBehavior.REJECT_COMMANDS)
.autoReconnect(true)
.build();
return LettuceClientConfiguration.builder()
.readFrom(ReadFrom.REPLICA_PREFERRED)
.clientOptions(options)
.clientResources(dcr)
.build();
}
#Bean
StringRedisTemplate redisTemplate(RedisConnectionFactory redisConnectionFactory) {
return new StringRedisTemplate(redisConnectionFactory);
}
private RedisURI toRedisURI(String url) {
String[] split = url.split(":");
String host = split[0];
int port;
if (split.length > 1) {
port = Integer.parseInt(split[1]);
} else {
port = 6379;
}
return RedisURI.create(host, port);
}
}
Please advise how to continue with troubleshooting.

Answer 1

When running everything (redis, replica and spring) inside the docker network you should be using port 6379 instead of 7001
7001 port can be used to connect from outside the container to it. But now you are trying to connect from container to container.
So change your environment variable to
SPRING_REDIS_REPLICAS=redis-replica-a:6379