redis-pg-redis-docker

database.yml

default: &default
  adapter: postgresql
  encoding: unicode
  database: <%= Rails.application.credentials[:pg_database] %>
  username: <%= Rails.application.credentials[:pg_username] %>
  password: <%= Rails.application.credentials[:pg_password] %>
  host: <%= Rails.application.credentials[:pg_host] %>
  port: <%= Rails.application.credentials[:pg_port] %>
  pool: 5

development:
  <<: *default
  database: my_dev
  username: pguser
  password: p@55w0rdpg
  host: localhost
  port: 55432

test:
  <<: *default
  database: my_test
  username: pguser
  password: p@55w0rdpg
  host: localhost
  port: 55432

staging:
  <<: *default

production:
  <<: *default

docker-compose.yml

version: '3'

services:
  pg:
    image: postgres:11.2-alpine
    ports:
      - '55432:5432'
    volumes:
      - ${HOME}/.docker-volumes/pg-data:/var/lib/postgresql/data
    environment:
      - POSTGRES_PASSWORD=p@55w0rdpg
      - POSTGRES_USER=pguser
  redis:
    image: redis:5.0.3-alpine
    ports:
      - '56379:6379'
    volumes:
      - ${HOME}/.docker-volumes/redis-data:/data

RailsPgRedisDocker.md

Config Rails to use Postgres and Redis in docker