Heroku Buildpack for Elixir
Features
- Easy configuration with
elixir_buildpack.config
file - Use prebuilt Elixir binaries
- Allows configuring Erlang
- If your app doesn't have a Procfile, default web task
mix run --no-halt
will be run. - Consolidates protocols
- Hex and rebar support
- Caching of Hex packages, Mix dependencies and downloads
- Compilation procedure hooks through
hook_pre_compile
,hook_compile
,hook_post_compile
configuration
Version support
- Erlang - Prebuilt packages (17.5, 17.4, etc)
- The full list of prebuilt packages can be found here:
- gigalixir-20 or heroku-20 stacks: https://builds.hex.pm/builds/otp/ubuntu-20.04/builds.txt
- heroku-22 stacks: https://builds.hex.pm/builds/otp/ubuntu-22.04/builds.txt
- All other stacks: https://github.com/HashNuke/heroku-buildpack-elixir-otp-builds/blob/master/otp-versions
- The full list of prebuilt packages can be found here:
- Elixir - Prebuilt releases (1.0.4, 1.0.3, etc) or prebuilt branches (master, v1.7, etc)
- The full list of releases can be found here: https://github.com/elixir-lang/elixir/releases
- The full list of branches can be found here: https://github.com/elixir-lang/elixir/branches
Note: you should choose an Elixir and Erlang version that are compatible with one another.
Cloud Native Support
- Cloud Native users should use this buildpack
This buildpack is not guaranteed to be Cloud Native compatible. The elixir-buildpack/cloud-native-buildpack is a buildpack that is actively under development and is designed specifically to follow the Cloud Native Buildpack conventions.
Usage
Create a Heroku app with this buildpack
heroku create --buildpack hashnuke/elixir
Set the buildpack for an existing Heroku app
heroku buildpacks:set hashnuke/elixir
Use the edge version of buildpack
The hashnuke/elixir
buildpack contains the latest published version of the buildpack, but you can use the edge version (i.e. the source code in this repo) by running:
heroku buildpacks:set https://github.com/HashNuke/heroku-buildpack-elixir.git
When you decide to use the published or the edge version of the buildpack you should be aware that, although we attempt to maintain the buildpack for as many old Elixir and Erlang releases as possible, it is sometimes difficult since there's a matrix of 3 variables involved: Erlang version, Elixir version and Heroku stack. If your application cannot be updated for some reason and requires an older version of the buildpack then use a specific version of buildpack.
Use a specific version of buildpack
The methods above always use the latest version of the buildpack code. To use a specific version of the buildpack, choose a commit from the commits page. The commit SHA forms part of your buildpack url.
For example, if you pick the commit "883f33e10879b4b8b030753c13aa3d0dda82e1e7", then the buildpack url for your app would be:
https://github.com/HashNuke/heroku-buildpack-elixir.git#883f33e10879b4b8b030753c13aa3d0dda82e1e7
It is recommended to use a buildpack url with a commit SHA on production apps. This prevents the unpleasant moment when your Heroku build fails because the buildpack you use just got updated with a breaking change. Having buildpacks pinned to a specific version is like having your Hex packages pinned to a specific version in mix.lock
.
Using Heroku CI
This buildpack supports Heroku CI.
- To enable viewing test runs on Heroku, add tapex to your project.
- To detect compilation warnings use the
hook_compile
configuration option set tomix compile --force --warnings-as-errors
.
Elixir Releases
This buildpack can optionally build an Elixir release. The release build will be run after hook_post_compile
.
WARNING: If you need to do further compilation using another buildpack, such as the Phoenix static buildpack, you probably don't want to use this option. See the Elixir release buildpack instead.
To build and use a release for an app called foo
compiled with MIX_ENV=prod
:
- Make sure
elixir_version
inelixir_buildpack.config
is at least 1.9 - Add
release=true
toelixir_buildpack.config
- Use
web: _build/prod/rel/foo/bin/foo start
in your Procfile
NOTE: This requires the master version of the buildpack (or a commit later than 7d369c)
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=18.2.1
# Elixir version
elixir_version=1.2.0
# Always rebuild from scratch on every deploy?
always_rebuild=false
# Create a release using `mix release`? (requires Elixir 1.9)
release=true
# A command to run right before fetching dependencies
hook_pre_fetch_dependencies="pwd"
# A command to run right before compiling the app (after elixir, .etc)
hook_pre_compile="pwd"
hook_compile="mix compile --force --warnings-as-errors"
# A command to run right after compiling the app
hook_post_compile="pwd"
# Set the path the app is run from
runtime_path=/app
# Enable or disable additional test arguments
test_args="--cover"
Migrating from previous build pack
the following has been deprecated and should be removed from elixir_buildpack.config
:
# Export heroku config vars
config_vars_to_export=(DATABASE_URL)
Specifying Elixir version
- Use prebuilt Elixir release
elixir_version=1.2.0
- Use prebuilt Elixir branch, the branch specifier ensures that it will be downloaded every time
elixir_version=(branch master)
Specifying Erlang version
- You can specify an Erlang release version like below
erlang_version=18.2.1
Specifying config vars to export at compile time
- To set a config var on your heroku node you can exec from the shell:
heroku config:set MY_VAR=the_value
Other notes
-
Add your own
Procfile
to your application, else the default web taskmix run --no-halt
will be used. -
Your application should build embedded and start permanent. Build embedded will consolidate protocols for a performance boost, start permanent will ensure that Heroku restarts your application if it crashes. See below for an example of how to use these features in your Mix project:
defmodule MyApp.Mixfile do use Mix.Project def project do [app: :my_app, version: "0.0.1", build_embedded: Mix.env == :prod, start_permanent: Mix.env == :prod] end end
-
The buildpack will execute the commands configured in
hook_pre_compile
and/orhook_post_compile
in the root directory of your application before/after it has been compiled (respectively). These scripts can be used to build or prepare things for your application, for example compiling assets. -
The buildpack will execute the commands configured in
hook_pre_fetch_dependencies
in the root directory of your application before it fetches the application dependencies. This script can be used to clean certain dependencies before fetching new ones.
Development
- Build scripts to build erlang are at https://github.com/HashNuke/heroku-buildpack-elixir-otp-builds
- Sample app to test is available at https://github.com/HashNuke/heroku-buildpack-elixir-test
Testing
To run tests
git clone https://github.com/HashNuke/heroku-buildpack-elixir
export BUILDPACK="$(pwd)/heroku-buildpack-elixir"
git clone https://github.com/jesseshieh/heroku-buildpack-testrunner
git clone https://github.com/jesseshieh/shunit2
export SHUNIT_HOME="$(pwd)/shunit2"
cd heroku-buildpack-testrunner
bin/run $BUILDPACK
See more info at https://github.com/jesseshieh/heroku-buildpack-testrunner/blob/master/README.md
Credits
© Akash Manohar under The MIT License. Feel free to do whatever you want with it.