Grails 2.x is deprecated with support ending June 1, 2017
Your Grails 2.x apps will continue to work on Heroku, but the buildpack will no longer be automatically detected after June 1, 2017. To continue using Grails 2.x, set the buildpack manually:
heroku buildpacks:set https://github.com/heroku/heroku-buildpack-grails
The buildpack will no longer receive updates of new JDK versions and framework point releases. While Heroku customer support does its best to lend a hand with unsupported languages/frameworks, we will no longer officially answer Grails 2.x technical questions.
We suggest upgrading your app to a newer 3.x version of the framework. After you’ve made the code changes necessary to support Grails 3.x, you can use the Gradle buildpack. Heroku customer support will continue to answer Grails 3.x technical questions.