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Rails 5 Quick Start with Docker and Webpacker

This project contains all you need to start developing web apps with Rails 5 using Webpack to manage your CSS and javascript assets, via the webpacker gem.

We'll use docker to run our code, webpack server, and database, so this development environment can be used in any OS environment. If you mess up or something goes wrong, feel free to delete your containers and try again - that's what they're there for.

Prerequisites

Getting Started

Download the contents of this repo (except for this README) to a directory on your computer that you want to contain your new Rails app.

For example: ~/Projects/myapp/

You should name your directory whatever you want your Rails app to be named.

  • Dockerfile - Defines the dependencies of the container that our Rails app will run in. We start with a base image, FROM, that includes Ruby, Node, and Yarn.
  • docker-compose.yml - Defines the services that make up our application. To get started all we need is a database, a web server where Rails will run, and a webpack server that will serve and hot reload our assets. The postgres db is created using a pre-made image, while the webpack and web services are built using our Dockerfile.
  • Gemfile - A basic gemfile that just describes what version of Rails we want. When we create and install our app this file will be overwritten with all of Rails dependencies.

Create database volume

Run

docker volume create --name=pgdata

Docker containers are ephemeral. You can destroy and recreate them as often as you want. This volume will allow our DB data to survive such purges.

There is another way to do this: instead of creating a Docker volume, you can use the volumes attribute under the db service, and mount a local directory (./tmp/db):

db:
  image: postgres
  volumes:
    - ./tmp/db:/var/lib/postgresql/data

You could then delete the top level volumes attribute:

volumes:
  pgdata:
    external: true

However, due to file ownership issues, this approach won't work on Windows and you'll need to stick with using a Docker volume.

Create rails application

Run:

docker-compose run --no-deps web rails new . --force --database=postgresql --skip-sprockets --skip-coffee --skip-test --webpack

This will run the rails new command on our web service defined in docker-compose.yml.

Flag explanations:

  • --no-deps - Tells docker-compose run not to start any of the services in depends_on.
  • --force - Tells rails to overwrite existing files, such as Gemfile.
  • --database=postgresql - Tells Rails to default our db config to use postgres.
  • --skip-sprockets - Since we're using webpacker we don't need sprockets or the asset pipeline.
  • --skip-coffee - We're going to be writing ES6 JS, so we don't need coffeescript.
  • --skip-test - We're going to install Rspec, so we don't need the unit test framework that comes with rails.
  • --webpack - Tells Rails to go ahead and install webpack.

If everything went well you should have a directory full of Rails boilerplate.

Re-build web image

Run

docker-compose build

Since we now have a new Gemfile with all of our Rails gem dependencies defined, we need to rebuild our web image. This will re-execute the Dockerfile to build our image. Anytime you change your gemfile or tweak your Dockerfile, you'll need to rebuild.

Configure database

Next open config/database.yml.

It's already configured for postgres, but we need some additional configuration to get it to work with our db container.

Change the &default config to match the following:

default: &default
  adapter: postgresql
  encoding: unicode
  # For details on connection pooling, see Rails configuration guide
  # http://guides.rubyonrails.org/configuring.html#database-pooling
  pool: <%= ENV.fetch("RAILS_MAX_THREADS") { 5 } %>
  host: db
  username: postgres
  password:

This uses the default username and password (which is empty) for the postgres image. It also changes host to point to db, the name of our service.

Configure Webpacker

Similar to the database, we need to point our webpacker config at our running webpack service. In webpacker.yml, change

host: 0.0.0.0

and

public: 0.0.0.0:3035

to

host: webpack

and

public: webpack:3035

Start the application

Run

docker-compose up

This will start all of our services. You should see the Rails app server running:

web_1      | Puma starting in single mode...
web_1      | * Version 3.12.1 (ruby 2.5.5-p157), codename: Llamas in Pajamas
web_1      | * Min threads: 5, max threads: 5
web_1      | * Environment: development
web_1      | * Listening on tcp://0.0.0.0:3000
web_1      | Use Ctrl-C to stop

Create database

In another terminal, run:

docker ps

You should see all three defined services running.

Run:

docker-compose run web rake db:create

This will build our development and test databases.

Visit application

In your browser, go to http://localhost:3000. You should be greeted by the Rails splash image.

Install Javascript dependencies

Run

docker-compose run web yarn add turbolinks rails-ujs activestorage

This will use yarn to install these javascript libraries as dependencies of our app.

Next, in ./app/javascript/packs/application.js, add the following:

import Rails from 'rails-ujs';
import Turbolinks from 'turbolinks';
import * as ActiveStorage from 'activestorage';

Rails.start();
Turbolinks.start();
ActiveStorage.start();

This imports those libraries into our main application pack.

Then, in ./app/views/layouts/application.html.erb, change stylesheet_link_tag and javascript_include_tag to stylesheet_pack_tag and javascript_pack_tag. This will make our main application layout include our javascript and css packs. The CSS pack doesn't exist yet, we will create it in the next, optional step.

Install a CSS library (optional)

In this example we are using Bulma, but you could use Twitter bootstrap or any other CSS framework.

Run

docker-compose run web yarn add bulma

Next, create a new file, ./app/javascript/packs/application.scss, and add the following code:

@import '~bulma/bulma';

Install rspec

Follow these directions to install Rspec: https://github.com/rspec/rspec-rails#installation

Remember that you'll need to docker-compose build after adding the gem to your Gemfile, and you'll need to use docker-compose run web to run the rails generate command.

Build Your Application

You're now ready to take your application in whatever direction you choose.