Creating Elixir Phoenix Releases in Docker Container

There are several approaches to run a Phoenix Application within a Docker container:

1. Default mix development server mix phoenix.server
2. Elixir Release Manager exrm
3. The successor of exrm named distillery

The Docker images are using Alpine lightweight Linux distribution and are based on the images from msaraiva.

The repo contains the source code and the Dockerfile for these three solutions apllied to the default HelloPhoenix demo application from the Up And Running Guide.

Using the default mix development server

This is the simplest approach for housing a Phoenix application in a Docker container. It just uses the Cowboy HTTP server that is started when running the command mix phoenix.server. This is an easy solution which is applicable for development but it should not be used in a production environment. It is described in the Phoenix Docs.

The required steps are as follows:

1. mix phoenix.new hello_phoenix --no-brunch --no-ecto
2. docker build -t simple_cowboy_server .
3. docker run --rm -p 4000:4000 simple_cowboy_server

Advanced deployment using the Elixir Release Manager (exrm)

The Elixir Release Manager creates a compiled stand-alone bundle of the application so distributing the source code to the production server can be avoided. The system parameters for build system should be identical to the production system. This can be easily accomplished by utilizing docker containers.

These are the required steps:

1. mix phoenix.new hello_phoenix --no-brunch --no-ecto
2. Add {:exrm, "~> x.x.x"} to the deps in mix.exs
3. Define which servers are started for which endpoints in config/$MIX_ENV.exs, e.g. config :hello_phoenix, HelloPhoenix.Endpoint, server: true
4. Create docker image: docker build -t advanced_deployment_with_exrm .
5. Start docker image on production port 80: docker run --rm -p 80:80 advanced_deployment_with_exrm

In this example the building happens in the image where also the server is running. As a consequence the source code is also shipped in the docker container to the production envirnoment. To avoid this, either remove everything except the rel directory or create a separate container for building.

Advanced deployment using Distillery

Exrm will be replaced by Distillery soon.

Description will follow soon.