Ruby Buildpack now detects Rails configuration

Change effective on 12 June 2018

The Ruby buildpack now detects rails configuration. This feature is used to warn for problematic configuration.

For example, an app that is using Active Storage with this configuration will appear to work, but when the dyno restarts the assets uploaded will not be present due to Heroku’s ephemeral file system:

config.active_storage.service = :local

These types of issues are difficult to debug after the fact, so the Ruby buildpack now tries to detect them and proactively warn about this behavior.

This configuration should take no longer than the time it takes to boot your application or run a rake -T command. For most applications, this will take 5 seconds or less.

There is the chance that detection may take longer and it, therefore, has a timeout of 65 seconds. If your build is already close to the build timeout limit, this detection logic may cause it to go over. To decrease the amount of time it takes to detect configuration, we recommend using the bootsnap gem on your application.