heroku-buildpack-ruby-monorepo

This is a Heroku Buildpack for Ruby, Rack, and Rails apps which are not in top-level of the repository. It relies on unchanged Heroku Buildpack for Ruby under the hood.

Synopsis

Let's say you have following repository structure:

.
├── ecommerce
│   ├── crm
│   ├── ordering
│   ├── payments
│   ├── pricing
│   └── product_catalog
└── rails_application
    ├── Gemfile
    ├── Gemfile.lock
    ├── Rakefile
    ├── app
    ├── bin
    ├── config
    ├── config.ru
    ├── db
    ├── lib
    ├── log
    ├── public
    ├── test
    ├── tmp
    └── vendor

There's a Rails application under rails_application/. There's also ecommerce/ — a bunch of components this app relies on, but not the other way round.

Now, you want to promote rails_application/ to Heroku dyno:

• pushing subdirectory via git subtree push --prefix rails_application heroku master would cut you off from the component dependencies

• same issue with other popular monorepo buildpacks, which only promote chosen subdirectory to root

• packaging and distributing components as gems introduces burden when introducing changes and releasing them, quickly defeating benefits of the monorepo

• collapsing everything into a single, top-level package/bundle just for the deployment simply makes production debugging much worse

Luckily with this buildpack, there's no need for compromises!

Tell it where your application lives via APP_DIR variable and it will do the rest:

• preserve exactly the same directory structure on Heroky dyno

• execute stock, up-to-date Ruby buildpack at the application root

• ensure $PATH and $GEM_PATH are aware of given application root

• copy Procfile from application root to top-level directory, making necessary path changes so that Heroku recognizes avaiable process types and can instantly run web

So what do you have to do to use it?

Set it as your only buildpack first:

heroku buildpacks:set https://github.com/arkency/heroku-buildpack-ruby-monorepo

Let it know, where the application is:

heroku config:set APP_DIR=rails_application

Known limitations

• hardcoded Ruby buildpack, there was no need to make it generic so far

After all it is not a very sophisticated Heroku buildpack.