Build an environment of Ruby2.7.x + Rails6.0.x + MySQL8.0.x with Docker

The environment created by Sample in docker was Ruby2.5 + Rails5 + PostgreSQL, which was old and PostgreSQL, so It is rewritten for each new version Ruby2.7 & Rails6.0 & MySQL8.0.

• As of June 8, 2020, it will be Ruby2.7.1, Rails6.0.3.1, MySQL8.0.20.

File preparation

1. Dockerfile

• Gemfile
• Gemfile.lock
• entrypoint.sh
• docker-compose.yml
• .env

• You have already installed docker and docker-compose.
• Name the application myapp and replace it if you want to change it.

1. Preparation of Dockerfile

FROM ruby:2.7
# or latest

#nodejs and mysql-client (default-mysql-client)Installation of
RUN apt-get update -qq && apt-get install -y curl apt-transport-https wget nodejs default-mysql-client

#Install Yarn
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 yarn

RUN mkdir /myapp
WORKDIR /myapp
COPY Gemfile /myapp/Gemfile
COPY Gemfile.lock /myapp/Gemfile.lock
RUN bundle install
COPY . /myapp

# 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 3000

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

• It seems that mariadb-client is okay for default-mysql-client (see below)
• Package: default-mysql-client (1.0.5)
• The story that mysql-client could not apt-get install in Circle CI and the CI environment was broken
• Rails6 is used, so you need to install yarn

2. Preparation of Gemfile

source 'https://rubygems.org'
gem 'rails', '~>6.0.0'

3. Prepare Gemfile.lock

$ touch Gemfile.lock

• If you do not create an empty file, COPY Gemfile.lock /myapp/Gemfile.lock described in Dockerfile will fail.

Step 7/14 : COPY Gemfile.lock /myapp/Gemfile.lock
ERROR: Service 'web' failed to build: COPY failed: stat /var/lib/docker/tmp/docker-builder424702045/Gemfile.lock: no such file or directory

4. Prepare 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 "$@"

• Leave Sample in docker

5. Prepare docker-compose.yml

version: '3'
services:
  db:
    image: mysql:8.0 # or lates:
    environment:
      - MYSQL_ROOT_PASSWORD=${DB_ROOT_PASSWORD}
      - MYSQL_USER=${DB_USER}
      - MYSQL_PASSWORD=${DB_PASSWORD}
    volumes:
      - db-data:/var/lib/mysql
    command: --default-authentication-plugin=mysql_native_password
    ports:
      - ${DB_PORT}:3306
  web:
    build: .
    env_file: .env
    command: bash -c "rm -f tmp/pids/server.pid && bundle exec rails s -p 3000 -b '0.0.0.0'"
    volumes:
      - .:/myapp
      - bundle-data:/usr/local/bundle
    ports:
      - "3000:3000"
    depends_on:
      - db
volumes:
  db-data:
  bundle-data:

• MYSQL_ROOT_PASSWORD must be specified at a minimum
• See Docker Hub Environment Variables for other environment variables that can be set in MySQL with ʻenvironment`.
• Describe $ {variable name} to refer to the value set in the .env file described later.
• In mysql8, it is necessary to specify --default-authentication-plugin = mysql_native_password by changing the default authentication method.
• MySQL8.0 new feature (caching_sha2_password authentication plugin)
• Description for connecting to MySQL 8.0 from Linux-based Docker
• Write ʻenv_file: .env` so that it can be referenced in Rails
• The DB side is specified by ʻenvironment, but ʻenv_file: .env is also possible.

6. Prepare .env

DB_ROOT_PASSWORD=mysql_root_password
DB_USER=myapp
DB_PASSWORD=myapp_password
DB_PORT=3306

• Describe the value to be referenced in the above docker-compose.yml

This completes the file preparation. Here is what I have described so far. https://github.com/madai0517/rails6-mysql8_docker

Build execution

rails new

$ docker-compose run web rails new . --force --no-deps --database=mysql --webpacker --skip-test
$ sudo chown -R $USER:$USER . #Required for Linux. Not required if you're on a Mac

• Since DB is set to mysql, change to --database = mysql.
• Add --skip-test because I think I often use Rspec instead of Minitest
• If you forget to add --webpacker, you will need to run $ docker-compose run web rails webpacker: install later.
• If you have already installed mysql with homebrew and have already used port: 3306, it will be moss, so stop it with $ brew services stop mysql (mysql part is appropriately named Formulae)

DB connection settings

default: &default
  adapter: mysql2
  encoding: utf8mb4
  pool: <%= ENV.fetch("RAILS_MAX_THREADS") { 5 } %>
  username: <%= ENV['DB_USER'] %>
  password: <%= ENV['DB_PASSWORD'] %>
  host: db

development:
  <<: *default
  database: myapp_development

test:
  <<: *default
  database: myapp_test

production:
  <<: *default
  database: myapp_production
  username: myapp
  password: <%= ENV['MYAPP_DATABASE_PASSWORD'] %>

• Describe the DB information set in .env
• The db specified in host is the same as the db described in docker-compose.yml.
• See Differences between ENV [] and ENV.fetch () [Rails / Ruby] for how to write ENV.

Start, grant permissions to DB users, create DB

$ docker-compose build
$ docker-compose up -d
$ docker-compose exec db mysql -uroot -p -e"GRANT ALL PRIVILEGES ON *.* TO 'myapp'@'%';FLUSH PRIVILEGES;"
$ docker-compose run web rails db:create

• Grant permissions to DB_USER (myapp in this case) after launching the container
• I wanted to refer to the environment variable MYSQL_USER but didn't know how to write it ...

This completes the environment construction. You should be able to see the usual screen by accessing http: // localhost: 3000 /.