To activate Redis and then have it accessed by the Micronaut application already in Platform.sh, it is necessary to modify two files.

1. Add the Redis service 

In your .platform/services.yaml file, include Persistent Redis with a valid supported version:

data:
    type: redis-persistent:6.0
    disk: 256

2. Add the Redis relationship 

In your .platform.app.yaml file, use the service name redisdata to grant the application access to Elasticsearch via a relationship:

relationships:
    redisdata: "data:redis"

3. Export connection credentials to the environment 

Connection credentials for Redis, like any service, are exposed to the application container through the PLATFORM_RELATIONSHIPS environment variable from the deploy hook onward. Since this variable is a base64 encoded JSON object of all of your project’s services, you’ll likely want a clean way to extract the information specific to Elasticsearch into it’s own environment variables that can be easily used by Micronaut. On Platform.sh, custom environment variables can be defined programmatically in a .environment file using jq to do just that:

export REDIS_HOST=$(echo $PLATFORM_RELATIONSHIPS|base64 --decode|jq -r ".redisdata[0].host")
export REDIS_PORT=$(echo $PLATFORM_RELATIONSHIPS|base64 --decode|jq -r ".redisdata[0].port")
export REDIS_URI=redis://${REDIS_HOST}:${REDIS_PORT}
export JAVA_OPTS="-Xmx$(jq .info.limits.memory /run/config.json)m -XX:+ExitOnOutOfMemoryError"

4. Connect to Redis 

Commit that code and push. The Redis instance is ready to be connected from within the Micronaut application.