Docker-Heroku-Phoenix

This is a Dockerfile and Docker image for use with Phoenix Framework apps on the Heroku Platform. This is a workflow that largely replaces git push and buildpacks and offers a higher level of dev-prod parity. For more on the workflow, checkout the Heroku Devcenter.

This image a bit more generic than the title lets on. It's not tied to any Phoenix libraries or Brunch, so it's feasible for use on any project that is built on Elixir and Node that you'd like to deploy to Heroku.

What this does:

• Starts from the base heroku/cedar:14 docker image.
• Builds and Installs Erlang from source.
• Builds and Installs Elixir from source.
• Builds and Installs Node.js from source.
• Installs Hex, the package manager for Elixir.
• Installs NPM, the package manager for Node.

Example Usage:

A Dockerfile for a vanilla Phoenix app going to prod would look like this:

FROM joshwlewis/docker-heroku-phoenix:latest

# Compile elixir files for production
ENV MIX_ENV prod
# This prevents us from installing devDependencies
ENV NODE_ENV production
# This causes brunch to build minified and hashed assets
ENV BRUNCH_ENV production

# We add manifests first, to cache deps on successive rebuilds
COPY ["mix.exs", "mix.lock", "/app/user/"]
RUN mix deps.get

# Again, we're caching node_modules if you don't change package.json
ADD package.json /app/user/
RUN npm install

# Add the rest of your app, and compile for production
ADD . /app/user/
RUN mix compile \
    && brunch build \
    && mix phoenix.digest

And your docker-compose would look like this:

web:
  build: .
  command: 'bash -c ''mix phoenix.server'''
  dockerfile: Dockerfile.prod
  working_dir: /app/user
  environment:
    LANG: en_US.UTF-8
    HOST: localhost
    PORT: 4000
    DATABASE_URL: 'postgres://postgres:@postgres:4000/api_prod'
  ports:
    - '4000:4000'
  links:
    - postgres
postgres:
  image: postgres