Ruby on Rails Docker development environment - based on blog post by Hint.io's Nate Vick https://hint.io/blog/rails-development-with-docker

docker-compose.yml

version: '3.7'

services:
  rails:
    build:
      context: .
      args:
        - RUBY_VERSION=2.6
        - BUNDLE_JOBS=15
        - BUNDLE_RETRY=2
        - NODE_VERSION=10
        - INSTALL_PG_CLIENT=true
        - UID=500
        - GID=500
    environment:
      - DATABASE_USER=postgres
      - DATABASE_HOST=postgres
    entrypoint: ./entrypoint.sh
    volumes:
      - .:/app:cached
      - gems:/gems
      - node_modules:/app/node_modules
      - packs:/app/public/packs
      - rails_cache:/app/tmp/cache
    ports:
      - "3000:3000"
    user: ruby
    tty: true
    stdin_open: true
    depends_on:
      - postgres
  postgres:
    image: postgres:11
    volumes:
      - postgres:/var/lib/postgresql/data

volumes:
  gems:
  postgres:
  node_modules:
  packs:
  rails_cache:

Dockerfile

ARG RUBY_VERSION=2.6
FROM ruby:$RUBY_VERSION
ARG DEBIAN_FRONTEND=noninteractive
ARG NODE_VERSION=11
RUN curl -sL https://deb.nodesource.com/setup_$NODE_VERSION.x | bash -
RUN curl -sS https://dl.yarnpkg.com/debian/pubkey.gpg | apt-key add - && \
  echo "deb https://dl.yarnpkg.com/debian/ stable main" | tee /etc/apt/sources.list.d/yarn.list

RUN apt-get update && apt-get install -y \
  build-essential \
  nodejs \
  yarn \
  locales \
  git \
  netcat \
  vim \
  sudo
ARG UID
ENV UID $UID
ARG GID
ENV GID $GID
ARG USER=ruby
ENV USER $USER

RUN groupadd -g $GID $USER && \
    useradd -u $UID -g $USER -m $USER && \
    usermod -p "*" $USER && \
    usermod -aG sudo $USER && \
    echo "$USER ALL=NOPASSWD: ALL" >> /etc/sudoers.d/50-$USER
ENV LANG C.UTF-8

ENV BUNDLE_PATH /gems
ENV BUNDLE_HOME /gems

ARG BUNDLE_JOBS=20
ENV BUNDLE_JOBS $BUNDLE_JOBS
ARG BUNDLE_RETRY=5
ENV BUNDLE_RETRY $BUNDLE_RETRY

ENV GEM_HOME /gems
ENV GEM_PATH /gems

ENV PATH /gems/bin:$PATH
#-----------------
# Postgres Client:
#-----------------
ARG INSTALL_PG_CLIENT=false

RUN if [ "$INSTALL_PG_CLIENT" = true ]; then \
    apt-get install -y postgresql-client \
;fi

RUN mkdir -p "$GEM_HOME" && chown $USER:$USER "$GEM_HOME"
RUN mkdir -p /app && chown $USER:$USER /app

WORKDIR /app

RUN mkdir -p node_modules && chown $USER:$USER node_modules
RUN mkdir -p public/packs && chown $USER:$USER public/packs
RUN mkdir -p tmp/cache && chown $USER:$USER tmp/cache

USER $USER

RUN gem install bundler

entrypoint.sh

#!/usr/bin/env bash
  set -e

  : ${APP_PATH:="/app"}
  : ${APP_TEMP_PATH:="$APP_PATH/tmp"}
  : ${APP_SETUP_LOCK:="$APP_TEMP_PATH/setup.lock"}
  : ${APP_SETUP_WAIT:="5"}

  # 1: Define the functions to lock and unlock our app container's setup
  # processes:
  function lock_setup { mkdir -p $APP_TEMP_PATH && touch $APP_SETUP_LOCK; }
  function unlock_setup { rm -rf $APP_SETUP_LOCK; }
  function wait_setup { echo "Waiting for app setup to finish..."; sleep $APP_SETUP_WAIT; }

  # 2: 'Unlock' the setup process if the script exits prematurely:
  trap unlock_setup HUP INT QUIT KILL TERM EXIT

  # 3: Wait for postgres to come up
  echo "DB is not ready, sleeping..."
  until nc -vz postgres 5432 &>/dev/null; do
    sleep 1
  done
  echo "DB is ready, starting Rails."

  # 4: Specify a default command, in case it wasn't issued:
  if [ -z "$1" ]; then set -- rails server -p 3000 -b 0.0.0.0 "$@"; fi

  # 5: Run the checks only if the app code is executed:
  if [[ "$1" = "rails" ]]
  then
    # Clean up any orphaned lock file
    unlock_setup
    # 6: Wait until the setup 'lock' file no longer exists:
    while [ -f $APP_SETUP_LOCK ]; do wait_setup; done

    # 7: 'Lock' the setup process, to prevent a race condition when the
    # project's app containers will try to install gems and set up the
    # database concurrently:
    lock_setup
    # 8: Check if dependencies need to be installed and install them
    bundle install

    yarn install
    # 9: Run migrations or set up the database if it doesn't exist
    # Rails >= 6
    bundle exec rails db:prepare
    # Rails < 6
    # bundle exec rake db:migrate 2>/dev/null || bundle exec rake db:setup

    # 10: 'Unlock' the setup process:
    unlock_setup

    # 11: If the command to execute is 'rails server', then we must remove any
    # pid file present. Suddenly killing and removing app containers might leave
    # this file, and prevent rails from starting-up if present:
    if [[ "$2" = "s" || "$2" = "server" ]]; then rm -rf /app/tmp/pids/server.pid; fi
  fi
  # 12: Replace the shell with the given command:
  exec "$@"