Heroku Buildpack for Ruby (MAPS fork)

This is a Heroku Buildpack for Ruby, Rack, and Rails apps. It uses Bundler for dependency management.

This buildpack requires 64-bit Linux.

Why create a MAPS-specific fork?

This is a fork of the officially-supported Ruby buildpack.

This fork is necessary because some of our Heroku-deployed applications (eg - RAD and RAD Consumer) use bower and the bowndler gem to manage frontend dependencies. At time of writing, the frontend team hasn't settled on a way to migrate away from bower in these apps.

Historically, we've deployed using a fork of a prior, now deprecated buildpack. There are a couple of issues with this approach:

• Our Heroku applications need to be upgraded from Cedar-14 to the Heroku-18 stack, as the former is end-of-life as of 1st May 2020. The old buildpack triggers a number of errors when used to deploy to heroku-18.
• The old buildpack is no longer maintained. Using a supported one instead allows us to merge upstream changes into this fork as and when they become available (for as long as we need to support the use of bower in our Heroku apps).

For these reasons, we've opted to replace our usage of the older fork with a more recent one.

Note that this buildpack relies on Heroku's multiple buildpack support to install Node before Ruby (see Usage notes below).

Usage

In addition to the code in the examples below, you'll need to set the nodejs buildpack to run first before trying to deploy.

$ heroku buildpacks:add --index 1 heroku/nodejs

Ruby

Example Usage:

$ ls
Gemfile Gemfile.lock

$ heroku create --buildpack https://github.com/heroku/heroku-buildpack-ruby.git

$ git push heroku master
...
-----> Heroku receiving push
-----> Fetching custom buildpack
-----> Ruby app detected
-----> Installing dependencies using Bundler version 1.1.rc
       Running: bundle install --without development:test --path vendor/bundle --deployment
       Fetching gem metadata from http://rubygems.org/..
       Installing rack (1.3.5)
       Using bundler (1.1.rc)
       Your bundle is complete! It was installed into ./vendor/bundle
       Cleaning up the bundler cache.
-----> Discovering process types
       Procfile declares types -> (none)
       Default types for Ruby  -> console, rake

The buildpack will detect your app as Ruby if it has a Gemfile and Gemfile.lock files in the root directory. It will then proceed to run bundle install after setting up the appropriate environment for ruby and Bundler.

Bundler

For non-windows Gemfile.lock files, the --deployment flag will be used. In the case of windows, the Gemfile.lock will be deleted and Bundler will do a full resolve so native gems are handled properly. The vendor/bundle directory is cached between builds to allow for faster bundle install times. bundle clean is used to ensure no stale gems are stored between builds.

Rails 2

Example Usage:

$ ls
app  config  db  doc  Gemfile  Gemfile.lock  lib  log  public  Rakefile  README  script  test  tmp  vendor

$ ls config/environment.rb
config/environment.rb

$ heroku create --buildpack https://github.com/heroku/heroku-buildpack-ruby.git

$ git push heroku master
...
-----> Heroku receiving push
-----> Ruby/Rails app detected
-----> Installing dependencies using Bundler version 1.1.rc
...
-----> Writing config/database.yml to read from DATABASE_URL
-----> Rails plugin injection
       Injecting rails_log_stdout
-----> Discovering process types
       Procfile declares types      -> (none)
       Default types for Ruby/Rails -> console, rake, web, worker

The buildpack will detect your app as a Rails 2 app if it has a environment.rb file in the config directory.

Rails Log STDOUT

A rails_log_stdout is installed by default so Rails' logger will log to STDOUT and picked up by Heroku's logplex.

Auto Injecting Plugins

Any vendored plugin can be stopped from being installed by creating the directory it's installed to in the slug. For instance, to prevent rails_log_stdout plugin from being injected, add vendor/plugins/rails_log_stdout/.gitkeep to your git repo.

Rails 3

Example Usage:

$ ls
app  config  config.ru  db  doc  Gemfile  Gemfile.lock  lib  log  Procfile  public  Rakefile  README  script  tmp  vendor

$ ls config/application.rb
config/application.rb

$ heroku create --buildpack https://github.com/heroku/heroku-buildpack-ruby.git

$ git push heroku master
-----> Heroku receiving push
-----> Ruby/Rails app detected
-----> Installing dependencies using Bundler version 1.1.rc
       Running: bundle install --without development:test --path vendor/bundle --deployment
       ...
-----> Writing config/database.yml to read from DATABASE_URL
-----> Preparing app for Rails asset pipeline
       Running: rake assets:precompile
-----> Rails plugin injection
       Injecting rails_log_stdout
       Injecting rails3_serve_static_assets
-----> Discovering process types
       Procfile declares types      -> web
       Default types for Ruby/Rails -> console, rake, worker

The buildpack will detect your apps as a Rails 3 app if it has an application.rb file in the config directory.

Assets

To enable static assets being served on the dyno, rails3_serve_static_assets is installed by default. If the execjs gem is detected then node.js will be vendored. The assets:precompile rake task will get run if no public/manifest.yml is detected. See this article on how rails 3.1 works on cedar.

Documentation

For more information about using Ruby and buildpacks on Heroku, see these Dev Center articles:

• Heroku Ruby Support
• Getting Started with Ruby on Heroku
• Getting Started with Rails 4 on Heroku
• Buildpacks
• Buildpack API

Hacking

To use this buildpack, fork it on Github. Push up changes to your fork, then create a test app with --buildpack <your-github-url> and push to it.

To change the vendored binaries for Bundler, Node.js, and rails plugins, use the rake tasks provided by the Rakefile. You'll need an S3-enabled AWS account and a bucket to store your binaries in as well as the vulcan gem to build the binaries on heroku.

For example, you can change the vendored version of Bundler to 1.1.rc.

First you'll need to build a Heroku-compatible version of Node.js:

$ export AWS_ID=xxx AWS_SECRET=yyy S3_BUCKET=zzz
$ s3 create $S3_BUCKET
$ rake gem:install[bundler,1.1.rc]

Open lib/language_pack/ruby.rb in your editor, and change the following line:

BUNDLER_VERSION = "1.11.2"

Open lib/language_pack/base.rb in your editor, and change the following line:

VENDOR_URL = "https://s3.amazonaws.com/zzz"

Commit and push the changes to your buildpack to your Github fork, then push your sample app to Heroku to test. You should see:

-----> Installing dependencies using Bundler version 1.1.rc

NOTE: You'll need to vendor the plugins, node, Bundler, and libyaml by running the rake tasks for the buildpack to work properly.

Testing

The tests on this buildpack are written in Rspec to allow the use of focused: true. Parallelization of testing is provided by https://github.com/grosser/parallel_tests this lib spins up an arbitrary number of processes and running a different test file in each process, it does not parallelize tests within a test file. To run the tests: clone the repo, then bundle install then clone the test fixtures by running:

$ bundle exec hatchet install

then go to hatchet repo and follow the instructions to set it up.

Now run the tests:

$ bundle exec parallel_rspec -n 6 spec/

If you don't want to run them in parallel you can still:

$ bundle exec rake spec

Now go take a nap or do something for a really long time.