Carl's dev blog

Notes from a polyglot programmer

Run JRuby on Heroku

A lot of different hacks has existed for a while now to run JRuby on Heroku but thanks to a new Heroku feature called buildpacks is now easy to implement and run your own runtime on Heroku.

I did therefore create a buildpack which basically downloads JRuby, install Bundler and run bundle install. After that it behaves exactly like a normal Heroku Ruby application!

Create a JRuby backed Heroku app
$ heroku create -s cedar --buildpack

Read more about the JRuby buildpack at

Take a look at an example application here:

Update 2012-04-22

The buildpack is moved and now maintained under the JRuby organization:

If you already have created an application with the old buildpack url you can just update the environment variable to the new url:

Change buildpack url
$ heroku config:add BUILDPACK_URL=