[Environment construction with Docker] Rails 6 & MySQL 8

1.First of all

This is a memorandum article because I built the environment with the intention of creating a new application with Rails. I have less than a year of experience as an engineer and Rails, so please point out any mistakes or better writing.

Operating environment

macOS Catalina 10.15.7
Ruby 2.7.2
Rails 6.0.3
MySQL 8.0.20
Docker 19.03.13
docker-compose 1.27.4

2. Prepare the necessary files

First, create an arbitrary directory and create a file.

mkdir rails_app
cd rails_app

#Create multiple files at once
touch {Dockerfile,docker-compose.yml,Gemfile,Gemfile.lock,entrypoint.sh,.env}

Dockerfile

`Dockerfile`


FROM ruby:2.7.2

ENV LANG C.UTF-8
ENV APP_ROOT /app

# install required libraries
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 && \
  apt-get update -qq && \
  apt-get install -y --no-install-recommends \
  build-essential \
  nodejs \
  yarn && \
  apt-get clean && \
  rm --recursive --force /var/lib/apt/lists/*

# create working directory
RUN mkdir $APP_ROOT
WORKDIR $APP_ROOT

# bundle install
COPY Gemfile $APP_ROOT/Gemfile
COPY Gemfile.lock $APP_ROOT/Gemfile.lock
RUN bundle install --jobs 4 --retry 3

# create app in container
COPY . $APP_ROOT

# 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 3000

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

docker-compose.yml

`docker-compose.yml`


version: '3.7'
services:
  db:
    image: mysql:8.0.20
    volumes:
      - mysql:/var/lib/mysql:delegated
    ports:
      - '3307:3306'
    command: --default-authentication-plugin=mysql_native_password
    env_file: .env

  web:
    build:
      context: .
      dockerfile: Dockerfile
    command: bash -c "rm -f tmp/pids/server.pid && bundle exec rails s -p 3000 -b '0.0.0.0'"
    tty: true
    stdin_open: true
    env_file: .env
    depends_on:
      - db
    ports:
      - '3000:3000'
    volumes:
      - .:/app:cached
      - bundle:/usr/local/bundle:delegated
      - node_modules:/app/node_modules
      - tmp-data:/app/tmp/sockets

volumes:
  mysql:
  bundle:
  node_modules:
  tmp-data:

.env

`.env`


MYSQL_ROOT_PASSWORD=password
TZ=Japan

Gemfile

`Gemfile`


source 'https://rubygems.org'
gem 'rails', '6.0.3'

Gemfile.lock

`Gemfile.lock`


#Leave empty

entrypoint.sh

`entrypoint.sh`


#!/bin/bash
set -e

# Remove a potentially pre-existing server.pid for Rails.
rm -f /myapp/tmp/pids/server.pid

# Then exec the container's main process (what's set as CMD in the Dockerfile).
exec "$@"

3. Create a Rails project

Once you have created the files you need, run the rails new command.

docker-compose run --rm web rails new . --force --no-deps --database=mysql --skip-turbolinks --skip-test
docker-compose run --rm web bin/rails webpacker:install

I think you can freely add options, but it is easier to specify various options here.

4. Edit database.yml

`database.yml`


default: &default
  adapter: mysql2
  encoding: utf8mb4
  pool: <%= ENV.fetch("RAILS_MAX_THREADS") { 5 } %>
  username: <%= ENV.fetch('MYSQL_USERNAME') { 'root' } %>
  password: <%= ENV.fetch('MYSQL_PASSWORD') { 'password' } %>
  host: <%= ENV.fetch('MYSQL_HOST') { 'db' } %>

development:
  <<: *default
  database: rails_app_dev

test:
  <<: *default
  database: rails_app_test

production:
  <<: *default
  database: rails_app_prd
  username: app
  password: hoge

Describe password etc. so that you can access with the information set in docker-compose.yml. host is a db container.

5. Build the Docker image and create a DB

docker-compose build
docker-compose run web bin/rails db:create

Yay! You’re on Rails!

docker-compose up -d

Start the container, and when the initial Rails screen is displayed, you're done.

reference

-[Rails] Rails 6.0 x Docker x MySQL environment construction --Participating projects, etc.