Buildpacks are an extremely powerful tool for specifying the ecosystem of tools and dependencies packaged with your Heroku application and controlling the way the application is built from code to a deployed app.

In the post announcing the release of buildpacks we illustrated this point, explaining how buildpacks provide the mechanism by which Heroku supports a variety of languages and frameworks, not just Ruby and Rails. We also briefly covered some of the end-user customizations that can be achieved with custom buildpacks, such as adding binary support and modifying the build process.

Today we'll examine the basic structure of buildpacks and study some example customizations to...

Last summer, Heroku became a polyglot platform, with official support for Ruby, Node.js, Clojure, Java, Python, and Scala. Building a platform that works equally well for such a wide variety of programming languages was a unique technical design challenge.

We knew from the outset that maintaining siloed, language-specific products – a Heroku for Ruby, a Heroku for Node.js, a Heroku for Clojure, and so on – wouldn't be scalable over the long-term.

Instead, we created Cedar: a single, general-purpose stack with no native support for any language. Adding support for any language is a matter of layering on a build-time adapter that can...