Deploying phoenix app to heroku as docker container

Pre-requisites

• Docker : http://docs.docker.com/v1.8/installation/
• Heroku toolbelt : https://toolbelt.heroku.com/

Install heroku docker plugin

heroku plugins:install heroku-docker

Copy app.json and Procfile

Copy app.json and Procfile from this repository to your 
phoenix application root folder

Change app name & description

Edit app.json to change name & description 

Create docker related files (Dockerfile and docker-compose.yml)

heroku docker:init

Append following lines to Dockerfile

# 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

Edit config/[dev|test|prod.secret].exs

# Configure your database
config :chatapp, Chatapp.Repo,
  adapter: Ecto.Adapters.Postgres,
  url: {:system, "DATABASE_URL"},
  pool_size: 20

Create a heroku app

heroku create

Push docker image to heroku

heroku docker:release

• Executing 'heroku docker:release' command for very first time will take some time, subsequent runs will be much quicker.

Creating database

No need to run "mix ecto.create" with heroku as we just use 
postgresql database in heroku, rather than creating it.

Running Ecto migrations

heroku run "cd /app/user;MIX_ENV=prod NODE_ENV=production BRUNCH_ENV=production mix ecto.migrate"

Open application URL in browser

heroku open

Miscellaneous heroku commands

Connect to postgresql cli

heroku pg:psql DATABASE

• Note: Run above command as it is, without replacing DATABASE with anything

Reset database

heroku pg:reset DATABASE_URL

• Note: Run above command as it is, without replacing DATABASE_URL with anything

Heroku logs

heroku logs -t --app <<app_name>>

Credit

Based on Docker image & instructions found at
https://hub.docker.com/r/joshwlewis/docker-heroku-phoenix/