mirror of https://github.com/docker/compose.git
100 lines
4.1 KiB
Markdown
100 lines
4.1 KiB
Markdown
---
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layout: default
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title: Getting started with Fig and Rails
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---
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Getting started with Fig and Rails
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==================================
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We're going to use Fig to set up and run a Rails/PostgreSQL app. Before starting, you'll need to have [Fig installed](install.html).
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Let's set up the three files that'll get us started. First, our app is going to be running inside a Docker container which contains all of its dependencies. We can define what goes inside that Docker container using a file called `Dockerfile`. It'll contain this to start with:
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FROM binaryphile/ruby:2.0.0-p247
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RUN apt-get update -qq && apt-get install -y build-essential libpq-dev
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RUN mkdir /myapp
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WORKDIR /myapp
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ADD Gemfile /myapp/Gemfile
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RUN bundle install
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ADD . /myapp
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That'll put our application code inside an image with Ruby, Bundler and all our dependencies. For more information on how to write Dockerfiles, see the [Dockerfile tutorial](https://www.docker.io/learn/dockerfile/) and the [Dockerfile reference](http://docs.docker.io/en/latest/reference/builder/).
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Next, we have a bootstrap `Gemfile` which just loads Rails. It'll be overwritten in a moment by `rails new`.
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source 'https://rubygems.org'
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gem 'rails', '4.0.2'
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Finally, `fig.yml` is where the magic happens. It describes what services our app comprises (a database and a web app), how to get each one's Docker image (the database just runs on a pre-made PostgreSQL image, and the web app is built from the current directory), and the configuration we need to link them together and expose the web app's port.
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db:
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image: orchardup/postgresql
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ports:
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- "5432"
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web:
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build: .
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command: bundle exec rackup -p 3000
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volumes:
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- .:/myapp
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ports:
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- "3000:3000"
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links:
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- db
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With those files in place, we can now generate the Rails skeleton app using `fig run`:
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$ fig run web rails new . --force --database=postgresql --skip-bundle
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First, Fig will build the image for the `web` service using the `Dockerfile`. Then it'll run `rails new` inside a new container, using that image. Once it's done, you should have a fresh app generated:
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$ ls
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Dockerfile app fig.yml tmp
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Gemfile bin lib vendor
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Gemfile.lock config log
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README.rdoc config.ru public
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Rakefile db test
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Uncomment the line in your new `Gemfile` which loads `therubyracer`, so we've got a Javascript runtime:
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gem 'therubyracer', platforms: :ruby
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Now that we've got a new `Gemfile`, we need to build the image again. (This, and changes to the Dockerfile itself, should be the only times you'll need to rebuild).
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$ fig build
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The app is now bootable, but we're not quite there yet. By default, Rails expects a database to be running on `localhost` - we need to point it at the `db` container instead. We also need to change the username and password to align with the defaults set by `orchardup/postgresql`.
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Open up your newly-generated `database.yml`. Replace its contents with the following:
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development: &default
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adapter: postgresql
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encoding: unicode
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database: myapp_development
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pool: 5
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username: docker
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password: docker
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host: <%= ENV.fetch('DB_1_PORT_5432_TCP_ADDR', 'localhost') %>
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port: <%= ENV.fetch('DB_1_PORT_5432_TCP_PORT', '5432') %>
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test:
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<<: *default
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database: myapp_test
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We can now boot the app.
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$ fig up
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If all's well, you should see some PostgreSQL output, and then—after a few seconds—the familiar refrain:
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myapp_web_1 | [2014-01-17 17:16:29] INFO WEBrick 1.3.1
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myapp_web_1 | [2014-01-17 17:16:29] INFO ruby 2.0.0 (2013-11-22) [x86_64-linux-gnu]
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myapp_web_1 | [2014-01-17 17:16:29] INFO WEBrick::HTTPServer#start: pid=1 port=3000
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Finally, we just need to create the database. In another terminal, run:
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$ fig run web rake db:create
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And we're rolling—see for yourself at [localhost:3000](http://localhost:3000) (or [localdocker:3000](http://localdocker:3000) if you're using docker-osx).
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