How to build Rails 6 environment with Docker

Introduction

I will introduce how to build a Rail 6 environment with Docker. Webpack was introduced from Rails6, and the procedure is a little different from Rails5, so I also considered that.

Docker official page Quickstart: Compose and Rails

environment

Docker3 Rails6.0.3 Ruby2.7.1 DB:PostgeSQL

1. Create the required files

This time, we will build the environment in a folder named "myapp". If you want to change the name, please change "myapp" accordingly.

The file structure to be created from now on is as follows.

file organization

myapp
  --Dockerfile
  --Gemfile
  --Gemfile.lock
  --entrypoint.sh
  --docker-compose.yml

First, create a folder.

Terminal

$ mkdir myapp
$ cd myapp

1.1 Dockerfile

Terminal

$ touch Dockerfile

Dockerfile

FROM ruby:2.7.1
RUN apt-get update -qq && apt-get install -y nodejs postgresql-client

##nodejs and yarn are required when installing webpack
#Install yarn package management tool
RUN apt-get update && apt-get install -y curl apt-transport-https wget && \
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 && apt-get install -y yarn

# Node.install js
RUN curl -sL https://deb.nodesource.com/setup_7.x | bash - && \
apt-get install nodejs

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"]

1.2 Gemfile

Terminal

$ touch Gemfile

Gemfile

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

1.3 Gemfile.lock

Terminal

$ touch Gemfile.lock

Nothing is listed here.

1.4 entrypoint.sh

Terminal

$ touch 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 "$@"

1.5 docker-compose.yml

Terminal

$ touch docker-compose.yml

docker-compose.yml

version: '3'
services:
  db:
    image: postgres
    volumes:
      - ./tmp/db:/var/lib/postgresql/data
    
    #######add to#########################
    environment:
      POSTGRES_HOST_AUTH_METHOD: 'trust'
    ###################################

  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

2. Build the project

2.1 rails new

Terminal

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

About command options --force: Overwrite the file even if it exists --no-deps: Do not start the linked service --database = postgresql: DB specifies PostgreSQL --skip-bundle: skip the bundle install (after creating the app)

2.2 docker-compose build Now that a new Gemfile has been created, use the following command to bundle install.

Terminal

$ docker-compose build

2.3 Change the connection settings to DB

config/database.yml

default: &default
  adapter: postgresql
  encoding: unicode
  pool: <%= ENV.fetch("RAILS_MAX_THREADS") { 5 } %>
  #####add to#####
  host: db
  username: postgres
  passowrd:
  #############

development:
  <<: *default
  database: myapp_development

test:
  <<: *default
  database: myapp_test

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

2.4 Confirmation of Docker container startup

Terminal

$ docker-compose up

It is OK if the container starts and connects to the server. I haven't created the DB yet, so I get the following error.

2.5 DB creation

Since I was able to connect to the server, I created a DB. After disconnecting with Ctrl + C

Terminal

  #Stop Docker once
$ docker-compose stop
$ docker-compose down
 
  #DB creation
$ docker-compose run web rake db:create

  #Launch Docker again
$ docker-compose up

3. Make sure the container & server is running

If you connect to [http: // localhost: 3000 /](http: // localhost: 3000 /), you can confirm that it has started successfully. The version is Rails6, Ruby2.7.1 as set.

Other

You need to use Docker commands when developing within Docker.

$ docker-compose run web bundle exec rails command

Example

$ docker-compose run web bundle exec rails g model User
$ docker-compose run web bundle exec rails g controller Homepages index
$ docker-compose run web bundle exec rails g rspec:install 

reference

Docker official page Quickstart: Compose and Rails Steps for building a Ruby on Rails environment with Docker [Rails 6 compatible] I was addicted to building a Rails 6 development environment with Docker Postgres Docker Image has changed and can no longer be started [Rails] ActiveRecord::NoDatabaseError [Docker]