mirror of https://github.com/docker/compose.git
175 lines
6.4 KiB
Markdown
175 lines
6.4 KiB
Markdown
<!--[metadata]>
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+++
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title = "Quickstart: Compose and Rails"
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description = "Getting started with Docker Compose and Rails"
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keywords = ["documentation, docs, docker, compose, orchestration, containers"]
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[menu.main]
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parent="workw_compose"
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weight=5
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+++
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<![end-metadata]-->
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## Quickstart: Docker Compose and Rails
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This Quickstart guide will show you how to use Docker Compose to set up and run a Rails/PostgreSQL app. Before starting, you'll need to have [Compose installed](install.md).
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### Define the project
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Start by setting up the three files you'll need to build the app. First, since
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your app is going to run inside a Docker container containing all of its
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dependencies, you'll need to define exactly what needs to be included in the
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container. This is done using a file called `Dockerfile`. To begin with, the
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Dockerfile consists of:
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FROM ruby:2.2.0
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RUN apt-get update -qq && apt-get install -y build-essential libpq-dev nodejs
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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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ADD Gemfile.lock /myapp/Gemfile.lock
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RUN bundle install
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ADD . /myapp
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That'll put your application code inside an image that will build a container
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with Ruby, Bundler and all your dependencies inside it. For more information on
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how to write Dockerfiles, see the [Docker user guide](https://docs.docker.com/engine/userguide/dockerimages/#building-an-image-from-a-dockerfile) and the [Dockerfile reference](https://docs.docker.com/engine/reference/builder/).
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Next, create 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', '4.2.0'
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You'll need an empty `Gemfile.lock` in order to build our `Dockerfile`.
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$ touch Gemfile.lock
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Finally, `docker-compose.yml` is where the magic happens. This file describes
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the services that comprise your app (a database and a web app), how to get each
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one's Docker image (the database just runs on a pre-made PostgreSQL image, and
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the web app is built from the current directory), and the configuration needed
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to link them together and expose the web app's port.
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version: '2'
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services:
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db:
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image: postgres
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web:
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build: .
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command: bundle exec rails s -p 3000 -b '0.0.0.0'
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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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depends_on:
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- db
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### Build the project
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With those three files in place, you can now generate the Rails skeleton app
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using `docker-compose run`:
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$ docker-compose run web rails new . --force --database=postgresql --skip-bundle
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First, Compose 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 generated a fresh app:
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$ ls -l
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total 56
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-rw-r--r-- 1 user staff 215 Feb 13 23:33 Dockerfile
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-rw-r--r-- 1 user staff 1480 Feb 13 23:43 Gemfile
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-rw-r--r-- 1 user staff 2535 Feb 13 23:43 Gemfile.lock
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-rw-r--r-- 1 root root 478 Feb 13 23:43 README.rdoc
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-rw-r--r-- 1 root root 249 Feb 13 23:43 Rakefile
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drwxr-xr-x 8 root root 272 Feb 13 23:43 app
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drwxr-xr-x 6 root root 204 Feb 13 23:43 bin
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drwxr-xr-x 11 root root 374 Feb 13 23:43 config
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-rw-r--r-- 1 root root 153 Feb 13 23:43 config.ru
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drwxr-xr-x 3 root root 102 Feb 13 23:43 db
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-rw-r--r-- 1 user staff 161 Feb 13 23:35 docker-compose.yml
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drwxr-xr-x 4 root root 136 Feb 13 23:43 lib
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drwxr-xr-x 3 root root 102 Feb 13 23:43 log
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drwxr-xr-x 7 root root 238 Feb 13 23:43 public
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drwxr-xr-x 9 root root 306 Feb 13 23:43 test
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drwxr-xr-x 3 root root 102 Feb 13 23:43 tmp
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drwxr-xr-x 3 root root 102 Feb 13 23:43 vendor
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If you are running Docker on Linux, the files `rails new` created are owned by
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root. This happens because the container runs as the root user. Change the
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ownership of the the new files.
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sudo chown -R $USER:$USER .
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If you are running Docker on Mac or Windows, you should already have ownership
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of all files, including those generated by `rails new`. List the files just to
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verify this.
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Uncomment the line in your new `Gemfile` which loads `therubyracer`, so you've
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got a Javascript runtime:
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gem 'therubyracer', platforms: :ruby
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Now that you've got a new `Gemfile`, you need to build the image again. (This,
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and changes to the Dockerfile itself, should be the only times you'll need to
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rebuild.)
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$ docker-compose build
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### Connect the database
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The app is now bootable, but you're not quite there yet. By default, Rails
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expects a database to be running on `localhost` - so you need to point it at the
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`db` container instead. You also need to change the database and username to
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align with the defaults set by the `postgres` image.
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Replace the contents of `config/database.yml` 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: postgres
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pool: 5
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username: postgres
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password:
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host: db
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test:
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<<: *default
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database: myapp_test
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You can now boot the app with:
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$ docker-compose up
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If all's well, you should see some PostgreSQL output, and then—after a few
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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 2.2.0 (2014-12-25) [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, you need to create the database. In another terminal, run:
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$ docker-compose run web rake db:create
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That's it. Your app should now be running on port 3000 on your Docker daemon. If you're using [Docker Machine](https://docs.docker.com/machine/), then `docker-machine ip MACHINE_VM` returns the Docker host IP address.
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>**Note**: If you stop the example application and attempt to restart it, you might get the
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following error: `web_1 | A server is already running. Check
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/myapp/tmp/pids/server.pid.` One way to resolve this is to delete the file
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`tmp/pids/server.pid`, and then re-start the application with `docker-compose
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up`.
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## More Compose documentation
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- [User guide](index.md)
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- [Installing Compose](install.md)
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- [Getting Started](gettingstarted.md)
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- [Get started with Django](django.md)
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- [Get started with WordPress](wordpress.md)
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- [Command line reference](./reference/index.md)
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- [Compose file reference](compose-file.md)
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