Heroku Buildpack for Elixir

Features

Easy configuration with elixir_buildpack.config file
Use prebuilt Elixir binaries or build from source
Mix dependency caching
Adds the free Heroku Postgres database upon app creation
DATABASE_URL is made available at compile time
Allows configuring Erlang
If your app doesn't have a Procfile, default web task mix server -p $PORT will be run.
Consolidates protocols
Hex and rebar support

Version support info

Erlang - Prebuilt packages (17.0, R16B03-1, etc)
Elixir - Prebuilt binaries or build from a branch, tag or a commit

Usage

Create a Heroku app with this buildpack

heroku create --buildpack "https://github.com/HashNuke/heroku-buildpack-elixir.git"

Set the buildpack of an existing Heroku app

heroku config:set BUILDPACK_URL="https://github.com/HashNuke/heroku-buildpack-elixir.git"

Configuration

Create a elixir_buildpack.config file in your app's root dir. The file's syntax is bash.

If you don't specify a config option, then the default option from the buildpack's elixir_buildpack.config file will be used.

Here's a full config file with all available options:

# Erlang version
erlang_version=17.0

# Elixir version
elixir_version=0.12.5

# Do dependencies have to be built from scratch on every deploy?
always_build_deps=false

Some other ways of specifying Elixir version

Build Elixir from a branch. If you specify a branch, that particular Elixir branch will be re-downloaded and built from source every time you deploy.

elixir_version=(branch master)

Build Elixir from a tag

elixir_version=(tag v0.12.5)

Build Elixir from a particular commit

elixir_version=(commit b07fbcf8b73e)

Specifying Erlang version

You can either specify a stable Erlang release version like below

erlang_version=R16B03-1

OR you can specify that Erlang builds from the master branch must be used

erlang_version=(branch master)

Note that if you specify the master branch of Erlang, then it is Heroku's periodic builds that will be used. I don't work for Heroku, but I'm assuming that's why they have master branch builds.

Other notes

Add your own Procfile to your application, else the default web task mix server -p $PORT will be used.
To make use of consolidated protocols they need to be added to the loadpath. Example: elixir -pa _build/prod/consolidated -S mix run --no-halt.
If you create an application with this buildpack, then a free database addonheroku-postgresql:hobby-dev is also added. The database credentials are available from the env var DATABASE_URL.

archie / heroku-buildpack-elixir