[Docker] Development environment construction Rails6 / Ruby2.7 / MySQL8


I had a hard time building the environment with Rails6 and MySQL with Docker, so I will leave a memorandum in the article as well.

As a stumbling block Unlike Rails5, Rails6 has required the introduction of Webpacker, a gem package for using Webpack with Ruby on Rails, which strongly supports modern front-end development.

Environment / version

Procedure to complete environment construction

  1. Prepare a project folder
  2. Prepare 5 files
  3. Describe each file
  4. Start Rails project (rails new)
  5. Build Docker image
  6. Edit database.yml
  7. Create DB (db: create)
  8. Start the container

Actually build the environment

1. Prepare a project folder

Create a folder with any name (it doesn't have to be a command)

mkdir dockerSampleApp 

2. Prepare 5 files

Create a file in the folder created in 1.

3. Describe each file


Regardless of the folder name of the project, the part of myapp can be left as myapp.


FROM ruby:2.7

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 nodejs yarn \
    && mkdir /myapp
WORKDIR /myapp
COPY Gemfile /myapp/Gemfile
COPY Gemfile.lock /myapp/Gemfile.lock
RUN bundle install
COPY . /myapp

COPY entrypoint.sh /usr/bin/
RUN chmod +x /usr/bin/entrypoint.sh
ENTRYPOINT ["entrypoint.sh"]

CMD ["rails", "server", "-b", ""]



version: '3'
    image: mysql:8.0
      MYSQL_ROOT_PASSWORD: password
      - '3306:3306'
    command: --default-authentication-plugin=mysql_native_password
      - mysql-data:/var/lib/mysql
    build: .
    command: bash -c "rm -f tmp/pids/server.pid && bundle exec rails s -p 3000 -b ''"
      - .:/myapp
      - "3000:3000"
      - db
    stdin_open: true
    tty: true
    driver: local



source 'https://rubygems.org'
gem 'rails', '~>6'



#Do not write anything in this file



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 "$@"

4. Start Rails project (rails new)

Execute command

$ docker-compose run web rails new . --force --no-deps --database=mysql --skip-test --webpacker --api

About options used this time

-- --force Overwrite existing Gemfile -- --no-deps Do not start the linked service -- --database = mysql Specify MySQL for the database -- --skip-test Skip the installation of Minitest (because the test will introduce RSpec) --"--webpackerInstall webpacker (required package management tool for Rails 6) ―― --api`` Since I want to make only API, execute it in API mode. As a result, unnecessary View / UI related libraries will not be installed.

5. Build Docker image

Image build means installing various dependent libraries and middleware, and installing and setting your own applications.

Execute command

$ docker-compose build

6. Edit database.yml

Corrected the relevant part of database.yml. Corrected the relevant part according to the settings of services and MYSQL_ROOT_PASSWORD in docker-compose.yml.


# ~abridgement~

default: &default
  adapter: mysql2
  encoding: utf8mb4
  pool: <%= ENV.fetch("RAILS_MAX_THREADS") { 5 } %>
  username: root
  password: password  # ->Correct the blank to password
  host: db  # ->Fixed from localhost to db

# ~abridgement~

7. Create DB (db: create)

Execute the command to create a DB

$ docker-compose run web rails db:create

8. Start the container

Finally execute the command to start the container

$ docker-compose up

It may take some time, but it's OK if such a log flows in the terminal

web_1  | => Booting Puma
web_1  | => Rails application starting in development 
web_1  | => Run `rails server --help` for more startup options
web_1  | Puma starting in single mode...
web_1  | * Version 4.3.6 (ruby 2.7.2-p137), codename: Mysterious Traveller
web_1  | * Min threads: 5, max threads: 5
web_1  | * Environment: development
web_1  | * Listening on tcp://
web_1  | Use Ctrl-C to stop

When I access localhost: 3000, the page is displayed safely. Should be! !!


I managed to build an environment! In the future, I would like to learn about infrastructure such as Docker and deepen my understanding!

Reference material

I was very helpful!

Thank you very much! !!

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