Docker Fig Live Rails

Get started with Rail Fig

We will now use Fig to configure and run a Rails/PostgreSQL app. Before you begin, make sure that Fig is already installed.

Three necessary documents need to be set up before all work can begin.
First, because the app is going to run in a Docker container that meets all the environmental dependencies, we can specify what the Docker container will install by editing the Dockerfile file. H ere's what it's all about:

FROM ruby
RUN apt-get update -qq && apt-get install -y build-essential libpq-dev
RUN mkdir /myapp
WORKDIR /myapp
ADD Gemfile /myapp/Gemfile
RUN bundle install
ADD . /myapp

The above specifies that the app will use a mirror with Ruby, Bundler, and its dependents installed. F or more information on how to write a Dockerfile file, you can view Mirror Creation and Dockerfile for use. N ext, we need a boot-loaded Rails file Gemfile After a while it will be rails new the rails new command.

source 'https://rubygems.org'
gem 'rails', '4.0.2'

Finally, fig.yml is the most magical place. fig.yml file associates everything. It describes the composition of the app (a web service and a database), the source of each mirror (the database runs using a predefined PostgreSQL image, the web app side is created from the local directory), the connection between the images, and the ports open to the service.

db:
  image: postgres
  ports:
    - "5432"
web:
  build: .
  command: bundle exec rackup -p 3000
  volumes:
    - .:/myapp
  ports:
    - "3000:3000"
  links:
    - db

When all the files are ready, we're ready to build the skeleton of the app by using the fig run command.

$ fig run web rails new . --force --database=postgresql --skip-bundle

Fig first uses Dockerfile a mirror for the web service, and then uses the image rails new subsequent commands in the container. Once this command is run, you should be able to see that a brand new app has been generated.

$ ls
Dockerfile   app          fig.yml      tmp
Gemfile      bin          lib          vendor
Gemfile.lock config       log
README.rdoc  config.ru    public
Rakefile     db           test

In Gemfile file, we remove the comment that loads the line therubyracer so that we can run the environment using Javascript:

gem 'therubyracer', platforms: :ruby

Now that we have a new Gemfile we need to re-create the image. (This step changes the Dockerfile file itself and only needs to be rebuilt once.)

$ fig build

The app is ready to start now, but the configuration is not yet complete. T he database target that Rails reads by default localhost and we need to manually specify the db of db S imilarly, the user name needs to be modified to match the postgres image intended. O pen the newly generated database.yml file. Replace with the following:

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

test:
  <<: *default
  database: myapp_test

You're ready to launch your app now.

$ fig up

If all goes well, you should be able to see the output of PostgreSQL, and after a few seconds you can see this repeated message:

myapp_web_1 | [2014-01-17 17:16:29] INFO  WEBrick 1.3.1
myapp_web_1 | [2014-01-17 17:16:29] INFO  ruby 2.0.0 (2013-11-22) [x86_64-linux-gnu]
myapp_web_1 | [2014-01-17 17:16:29] INFO  WEBrick::HTTPServer#start: pid=1 port=3000

Finally, what we need to do is create a database, open another terminal, and run:

$ fig run web rake db:create

This web app has already started listening to 3000 ports in your docker daemon (if you have a boot2docker, boot2docker ip you'll see its address).