Typical Rails + Docker Desktop Setup

docker-compose.yml

version: '3'
services:
  db:
    image: postgres:12-alpine
    volumes:
      - ./tmp/db:/var/lib/postgresql/data
      - ./tmp/backups:/backups

  # runs on localhost:30001
  pgadmin:
    image: dpage/pgadmin4
    environment:
      PGADMIN_DEFAULT_EMAIL: ${PGADMIN_DEFAULT_EMAIL:-user@example.com}
      PGADMIN_DEFAULT_PASSWORD: ${PGADMIN_DEFAULT_PASSWORD:-pass1234}
    volumes:
       - ./tmp/pgadmin:/root/.pgadmin
    ports:
      - "${PGADMIN_PORT:-30001}:80"
    restart: unless-stopped
    depends_on:
      - db

  redis:
    image: redis
    restart: unless-stopped

  # runs on localhost:3000
  web:
    # pass in your dotenv variables
    env_file:
      - .env.development
    environment:
      - REDIS_URL=redis://redis:6379/0
    build: .
    command: bash -c "rm -f tmp/pids/server.pid && bundle exec rails s -p 3000 -b '0.0.0.0'"
    volumes:
      # same as Dockerfile install location
      - .:/my-awesome-application
    ports:
      - "3000:3000"
    depends_on:
      - db
      - sidekiq
      - redis
    tty: true
    stdin_open: true
    restart: unless-stopped

  sidekiq:
    environment:
      - REDIS_URL=redis://redis:6379/0
    build: .
    volumes:
      # same as Dockerfile install location
      - .:/my-awesome-application
    depends_on:
      - redis
    command: bundle exec sidekiq
    restart: unless-stopped

  # you can docker attach to this node and interact with your specs that are running via guard-rspec
  guard:
    build: .
    volumes:
      # same as Dockerfile install location
      - .:/my-awesome-application
    environment:
      - RAILS_ENV=test
    command: bundle exec guard --no-bundler-warning
    #  add this line for no prompt --no-interactions
    tty: true
    stdin_open: true
    restart: unless-stopped

Dockerfile

FROM ruby:2.5-alpine

RUN apk add --update \
	    bash \
            build-base \
            nodejs  \
            postgresql-dev \
            postgresql-client \
            libxml2-dev \
            libxslt-dev \
            tzdata \
            && rm -rf /var/cache/apk/*

# Build variables you can override at runtime
ARG app_name=my-awesome-application
ARG port=3000

# Map Build variables to Environment
ENV app_name $app_name
ENV port $port

RUN mkdir /$app_name
WORKDIR /$app_name
COPY Gemfile /$app_name/Gemfile
COPY Gemfile.lock /$app_name/Gemfile.lock
# optional if no nokogiri
# RUN bundle config build.nokogiri --use-system-libraries
RUN bundle install
COPY . /$app_name

# Add a script to be executed every time the container starts.
COPY entrypoint.sh /usr/bin/
RUN chmod +x /usr/bin/entrypoint.sh
ENTRYPOINT ["entrypoint.sh"]

EXPOSE $port

# Start the main process.
CMD ["rails", "server", "-b", "0.0.0.0"]

Guard section assumes specs running via rspec-guard. You can eliminate if not needed. If used you can attach with

docker attach network-name_guard_1 <- network-name is usually = to your folder name

And detach without stopping the container with CNTRL+p+q Google docker commands for more information

Also if you use binding.pry or binding.irb in your webapp code, you can attach similarly to your web application and interact with it.

Optional:

• redis
• sidekiq
• pgadmin
• guard

would be started with
docker-compose build omit build if images are already made
docker-compose up -d -d daemonizes the images