You will notice that we have modified the engine template code available at http://predictionio.incubator.apache.org/templates/similarproduct/quickstart/ to meet Heroku needs.

The key things to understand from the engine code are as follows:

• Procfile: This file resides in the root of the project folder and declares the command necessary to run the app on Heroku dynos. Consider the following commands:

web: source bin/env.sh && target/universal/stage/bin/pio-engine-heroku -main ServerApp
train: source bin/env.sh && target/universal/stage/bin/pio-engine-heroku -main TrainApp

The preceding web command starts the code in the ServerApp Scala object when the Heroku dyno boots up.

• train: This is a custom command to train the app. The train basically runs the TrainApp object.