config/puma.rb Overwrites Engine Yard Configuration Options

When using Puma, if you commit a config/puma.rb file to your application's repository, it will override the Puma configuration generated by the Engine Yard platform and may prevent your application from successfully spawning Puma workers.

Workaround

Puma 2.8 and newer automatically creates $APP_ROOT/config/puma.rb.

If you need to keep the config/puma.rb file for local development, one way to address this is to rename the file to config/puma.rb.example, and commit that to your repository. Then, you can add an entry in your .gitignore to not commit config/puma.rb. At that point, you can have a local copy of config/puma.rb that is not stored in your repository, but if someone has a fresh checkout of the repository, they can just copy the config/puma.rb.example to config/puma.rb locally.