Introduction

Many companies are using Docker like CAMPFIRE or Money Forward, so I also wanted to use Docker.

First of all, I want to make Rails work with Docker, please refer to the official reference for genuine grammar.

Sample

Since this implementation result is put up on GitHub, please take a look it if it is good.

https://github.com/HiroyukiYagihashi/rails-on-docker

Implementation

Install Docker

Register to DockerHub and install Docker.

The Docker link above is for MacOS, but if you are using another OS, please install the appropriate Docker.

Create Project

First, create a folder appropriately.

I think that the project name will be myapp and I will create a project in this.

Create myapp folder

$ mkdir myapp
$ cd myapp

Create Dockerfile and implement the contents.

$ touch Dockerfile

FROM ruby:2.5
RUN apt-get update -qq && apt-get install -y nodejs postgresql-client
RUN 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"]
EXPOSE 3000

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

Next we will create Gemfile, Gemfile.lock.

Gemfile is created here to install Rails.

It will be overwritten when you execute rails new later.

No problem if Gemfile.lock is empty

Create Gemfile, Gemfile.lock

$ touch Gemfile && touch Gemfile.lock

Put in Gemfile's content

source 'https://rubygems.org'
gem 'rails', '~>5'

Here, we will create entrypoint.sh.

Currently, when a specific server.pid file exists, it seems that an error has occurred and prevents the server from restarting.

Adding this shell script will eliminate the above error.

Create entrypoint.sh

$ touch entrypoint.sh

Put in Gemfile's content 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 "$@"

Finally, create & put in docker-compose.yml's content

Create docker-compose.yml

$ touch docker-compose.yml

version: '3'
services:
  db:
    image: postgres
    ports:
      - '5432:5432'
    volumes:
      - postgresql-data:/var/lib/postgresql/data
  web:
    build: .
    command: bash -c "rm -f tmp/pids/server.pid && bundle exec rails s -p 3000 -b '0.0.0.0'"
    volumes:
      - .:/myapp
    ports:
      - "3000:3000"
    depends_on:
      - db
volumes:
  postgresql-data:
    driver: local

The necessary files have been created, finally those becomes such a file configuration.

myapp/ 　┣ Dockerfile 　┣ docker-compose.yml 　┣ entrypoint.sh 　┣ Gemfile 　┗ Gemfile.lock

Build Project

Now that you're ready to build, let's go ahead.

Docker execute rails new by Docker

$ docker-compose run web rails new . --force --no-deps --database=postgresql

$ docker-compose build

Database connection

Rails is configured to connect to the localhost database by default.

But this time, I change the setting to be connected to DB container (like PostgreSQL).

Change settings of database.yml

• config/database.yml

default: &default
  adapter: postgresql
  encoding: unicode
  host: db
  username: postgres
  password:
  pool: 5

development:
  <<: *default
  database: myapp_development

test:
  <<: *default
  database: myapp_test

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

Container creation & activation

$ docker-comnpose up

DB creation & migration

$ docker-compose run web rake db:create
$ docker-compose run web rails db:migrate

Displaying RailsWelcome page

Let's access http://localhost:3000/ with a browser.

Hooora,

If you want to terminate, don't forget the following command:

$ docker-compose down