GitLab CI example for Elixir (distillery, docker)

.gitlab-ci.yml

# This file is a template, and might need editing before it works on your project.
# This template uses the non default language docker image
# The image already has Hex installed.
image: alpine-elixir:1.4.0

# Pick zero or more services to be used on all builds.
# Only needed when using a docker container to run your tests in.
# Check out: http://docs.gitlab.com/ce/ci/docker/using_docker_images.html#what-is-service

variables:
  MODULE_NAME: "YOUR_MODULE"
  DOCKER_HUB: "YOUR_HUB"
  # ES_JAVA_OPTS: "-Xms512m -Xmx512m"

build:staging:
  stage: build
  cache:
    paths:
      - deps/
      - _build/
  variables:
    MIX_ENV: staging
  script:
   - mix do deps.get
   - mix release --env staging --verbose
  tags:
   - elixir
  artifacts:
    name: "staging"
    expire_in: 1 hour
    paths:
     - rel/$MODULE_NAME
     - Dockerfile
  only:
   - master

build:production:
  stage: build
  cache:
    paths:
      - deps/
      - _build/
  variables:
    MIX_ENV: prod
  script:
   - mix do deps.get
   - mix release --env prod --verbose
  tags:
   - elixir
  artifacts:
    name: "$CI_BUILD_TAG"
    expire_in: 1 hour
    paths:
     - rel/$MODULE_NAME
     - Dockerfile
  only:
   - tags

testing:
  stage: test
  # services:
  # - mongo:3.2
  # - elasticsearch:5.1
  cache:
    paths:
      - deps/
      - _build/
  variables:
    MIX_ENV: ci
  script:
   - mix do deps.get
   - mix test
  tags:
   - elixir
  only:
   - master
   - tags

staging:
  stage: deploy
  image: docker:latest
  services:
   - docker:dind
  environment: staging
  variables:
    DOCKER_DRIVER: overlay
    GIT_STRATEGY: none
  script:
   - docker build -t $DOCKER_HUB/$MODULE_NAME:staging .
   - docker push $DOCKER_HUB/$MODULE_NAME:staging
  dependencies:
   - build:staging
  tags:
   - docker-build
  only:
   - master

production:current:
  stage: deploy
  image: docker:latest
  services:
   - docker:dind
  environment: production
  variables:
    DOCKER_DRIVER: overlay
    GIT_STRATEGY: none
  script:
   - docker build -t $DOCKER_HUB/$MODULE_NAME:$CI_BUILD_TAG .
   - docker push $DOCKER_HUB/$MODULE_NAME:$CI_BUILD_TAG
  dependencies:
   - build:production
  tags:
   - docker-build
  only:
   - tags

production:latest:
  stage: deploy
  image: docker:latest
  services:
   - docker:dind
  environment: production
  variables:
    DOCKER_DRIVER: overlay
    GIT_STRATEGY: none
  script:
   - docker build -t $DOCKER_HUB/$MODULE_NAME:latest .
   - docker push $DOCKER_HUB/$MODULE_NAME:latest
  dependencies:
   - build:production
  tags:
   - docker-build
  only:
   - tags

config.exs

use Mix.Releases.Config,
    # This sets the default release built by `mix release`
    default_release: :default,
    # This sets the default environment used by `mix release`
    default_environment: :dev

# For a full list of config options for both releases
# and environments, visit https://hexdocs.pm/distillery/configuration.html


# You may define one or more environments in this file,
# an environment's settings will override those of a release
# when building in that environment, this combination of release
# and environment configuration is called a profile

environment :dev do
  set dev_mode: true
  set include_erts: true
  set cookie: "YOUR_COOKIE"
end

environment :staging do
  set include_erts: true
  set include_system_libs: true
  set include_src: false
  set cookie: "YOUR_COOKIE"
  set output_dir: "rel/YOUR_MODULE"
end

environment :prod do
  set include_erts: true
  set include_system_libs: true
  set include_src: false
  set cookie: "YOUR_COOKIE"
  set output_dir: "rel/YOUR_MODULE"
end

# You may define one or more releases in this file.
# If you have not set a default release, or selected one
# when running `mix release`, the first release in the file
# will be used by default

release :YOUR_MODULE do
  set version: current_version(:YOUR_MODULE)
end

Dockerfile

FROM alpine:3.6
LABEL maintainer="YOU"

# Important!  Update this no-op ENV variable when this Dockerfile
# is updated with the current date. It will force refresh of all
# of the base images and things like `apt-get update` won't be using
# old cached versions when the Dockerfile is built.
ENV REFRESHED_AT=2017-10-11 \
    MIX_ENV=prod

WORKDIR /opt/app

# Install deps
RUN \
    apk --no-cache upgrade && \
    # Install Erlang/OTP deps
    apk add --no-cache \
      ca-certificates \
      openssl-dev \
      ncurses-dev \
      unixodbc-dev \
      zlib-dev \
      bash

ADD ./rel/YOUR_MODULE .

HEALTHCHECK CMD bin/YOUR_MODULE ping

EXPOSE 80

CMD ["bin/YOUR_MODULE", "foreground"]