Getting Started

This is a brief tour on what is required to make a Phoenix application buildable through Drone and published as a minimal docker image.

.drone.sec.yml template

environment:
  SECRET_KEY_BASE: <phoenix application key>
  DOCKER_USERNAME: <docker username>
  DOCKER_EMAIL: <docker email address>
  DOCKER_PASS: <docker password>

If you need to generate a new phoenix secret, use the command mix phoenix.gen.secret from the application root.

Dockerfile template

FROM aweiker/alpine-elixir:1.2.1
ENV PORT=4000 MIX_ENV=prod

ENV APP_NAME=<app_name> APP_VERSION="<app_version>"

WORKDIR /$APP_NAME
ADD rel/$APP_NAME .
EXPOSE $PORT
CMD trap exit TERM; /$APP_NAME/bin/$APP_NAME foreground & wait

config/prod.exs

Update the config so that phoenix will run the server on startup, this can be accomplished by adding server: true to the call to config

For example:

config :hello_phoenix, HelloPhoenix.Endpoint,
  http: [port: {:system, "PORT"}],
  url: [host: "example.com", port: 80],
  cache_static_manifest: "priv/static/manifest.json",
  server: true

config/prod.secret.exs.tpl

This file will need to be automatically generated during image build time as this key is used to protect your production instance.

• Is it possible to use an environment variable for this?

Here is an example of the template for generating this file. Refer to the build steps in .drone.yml in particular the scripts/ci/generate_secrets.sh file.

use Mix.Config
config :hello_phoenix, HelloPhoenix.Endpoint,
  secret_key_base: "SECRET_KEY_BASE"

mix.exs

In order to bulid the release, exrm will need to be added as a dependency. With a default Phoenix application the dependencies will look like:

  defp deps do
    [
      {:phoenix, "~> 1.1.4"},
      {:phoenix_html, "~> 2.4"},
      {:phoenix_live_reload, "~> 1.0", only: :dev},
      {:gettext, "~> 0.9"},
      {:cowboy, "~> 1.0"},
      {:exrm, "~> 0.19.9"}
    ]
  end

.drone.yml

Drone allows you to run your build on one type of image and then publish against a different image. In this exmaple I am using bitwalker/alpine-elixir-phoenix to generate the build output. The reason for this is that this image is based on Alpine 3.3 and also has node installed on it. Since node is only needed at compile time the base image for our docker image does not have it and will be kept as minimal as possible. In addition to creating this .drone.yml file, the supporting script files will need to be copied over.

ANYTIME THIS FILE IS CHANGED, YOU WILL NEED TO REGENERATE .drone.sec.yml

build:
  image: bitwalker/alpine-elixir-phoenix:2.0
  commands:
    - scripts/ci/install_local_dependencies.sh
    - scripts/ci/execute_tests.sh
    - scripts/ci/generate_secrets.sh
    - scripts/ci/build_release.sh
  environment:
    - SECRET_KEY_BASE=$$SECRET_KEY_BASE

cache:
  mount:
    - deps
    - node_modules

publish:
  docker:
    username: $$DOCKER_USERNAME
    password: $$DOCKER_PASS
    email: $$DOCKER_EMAIL
    repo: drone-demos/drone-with-elixir
    tag:
      - latest
      - "0.0.$$BUILD_NUMBER"

Common Issues

All scripts need the execute permission in order to run

chmod +x scripts/ci/*.sh