Rails + MySQL + APIモードのDocker開発環境を作ってHerokuにデプロイする

$ mkdir app_name
$ cd app_name

FROM ruby:2.7.2
ENV LANG C.UTF-8

RUN apt update -qq && apt install -y mariadb-client

WORKDIR /app_name
COPY Gemfile /app_name/Gemfile
COPY Gemfile.lock /app_name/Gemfile.lock
RUN bundle install
COPY . /app_name

COPY entrypoint.sh /usr/bin/
RUN chmod +x /usr/bin/entrypoint.sh
ENTRYPOINT ["entrypoint.sh"]
EXPOSE 3000

CMD ["rails", "server", "-b", "0.0.0.0"]

version: '3'
services:
  web:
    build: .
    command: bash -c "rm -f tmp/pids/server.pid && bundle exec rails s -p 3000 -b '0.0.0.0'"
    volumes:
      - .:/app_name
    ports:
      - "3000:3000"
    depends_on:
      - db
    stdin_open: true
    tty: true
  db:
    image: mysql:8.0
    environment:
      MYSQL_ROOT_PASSWORD: password
    ports:
      - '3306:3306'
    command: --default-authentication-plugin=mysql_native_password
    volumes:
      - mysql_vol:/var/lib/mysql
volumes:
  mysql_vol:
    driver: local

#!/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 "$@"

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

$ touch Gemfile.lock

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

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

development:
  <<: *default
  database: app_name_development

test:
  <<: *default
  database: app_name_test

production:
  <<: *default
  url: <%= ENV['DATABASE_URL'] %>

$ heroku create app_name-20201027
Creating ⬢ app_name-20201027... done
https://app_name-20201027.herokuapp.com/ | https://git.heroku.com/app_name-20201027.git

$ heroku addons:create cleardb:ignite
Creating cleardb:ignite on ⬢ app_name-20201027... free
Created cleardb-deep-10722 as CLEARDB_DATABASE_URL
Use heroku addons:docs cleardb to view documentation

$ heroku config:get CLEARDB_DATABASE_URL
mysql://{ユーザー名}:{パスワード}@{ホスト名}/{データベース名}?reconnect=true

$ heroku config:add DATABASE_URL=mysql2://{ユーザー名}:{パスワード}@{ホスト名}/{データベース名}?reconnect=true

$ git push heroku master

$ docker-compose run --rm web mysql -h{ホスト名} -u{ユーザー名} -p{パスワード} {データベース名}