Dockerize Rails project with postgres and redis

Am new to RoR and I want to dockerize a Rails app with Redis and Postgres running in 3 different containers.

I now have a simple rails project running inside a container

How would I configure the RoR project to do the following:

1. How to connect Rails with Postgres?

2. How to setup Redis with Rails as a simple in-memory data store and access it?

Thanks :)

docker-compose.yml

version: '3'services:   rails:     build: .    volumes:      - ./:/app    ports:      - 3000:3000  postgres:    image: postgres  redis:    image: redis

EDIT:

Changed sqlite db to postgres