docker-compose.yml

database:
  image: postgres
  ports:
    - "5432"

redis:
  image: redis
  ports:
    - "6379"

worker:
  image: web
  environment:
    DATABASE_HOST: database
    DATABASE_PORT: 5432
    DATABASE_USER: postgres
    DATABASE_PASS: ''
    REDIS_URL: redis://redis:6379/0
    PORT: 3000
  command: bundle exec sidekiq
  volumes:
    - .:/app/someapp`
  links:
    - database
    - redis

web:
  build: .
  environment:
    DATABASE_HOST: database
    DATABASE_PORT: 5432
    DATABASE_USER: postgres
    DATABASE_PASS: ''
    REDIS_URL: redis://redis:6379/0
    PORT: 3000
  command: bundle exec rails server --port 3000 --binding 0.0.0.0
  volumes:
    - .:/app/someapp`
  ports:
    - "3000:3000"
  links:
    - database
    - redis

Dockerfile

FROM ruby:2.2.0

RUN apt-get update -qq && \
  apt-get install -y \
    build-essential \
    libpq-dev \
    postgresql-client \
    libxml2-dev \
    libxslt1-dev \
    nodejs && \
  rm -rf /var/lib/apt/lists/*

RUN apt-get update -qq && \
  apt-get install -y nodejs-legacy && \
  rm -rf /var/lib/apt/lists/*

RUN gem install --no-document bundler

# ################

ENV APP_NAME someapp
ENV APP_DIR /app/$APP_NAME

RUN mkdir -p /app && useradd -d $APP_DIR -m $APP_NAME

WORKDIR $APP_DIR

ADD Gemfile* $APP_DIR/

RUN bundle install --jobs 8

RUN chown -R $APP_NAME $APP_DIR

ADD . $APP_DIR