Heroku has a good getting started guide with Scala.

If you know the basic of Heroku, and has started with Typesafe’s Scala + Play! framework, there is 1 more thing you should to know.

You should know how to properly configure your local development environment.

Add the start script plugin

Typesafe’s start script plugin helps to generate a target/start script (you will use later).

Create the file project/build.sbt with this

resolvers += Classpaths.typesafeResolver

addSbtPlugin("com.typesafe.startscript" % "xsbt-start-script-plugin" % "0.5.3")

Procfile

Create the file Procfile in the root folder. Enter this line:

web: target/start Web

Build your app locally

You need to run this EVERYTIME before you run the app

$ sbt clean compile stage

Run your app locally

Run your app using foreman

$ foreman run

The app will run on port 5000 (instead of usual 9000).

Note: When you change your code, you need to exit, sbt clean compile run, then foreman start again..

Environment Variables (.env)

The .env file at root is for storing environment variables. This file is in .gitignore, because it usually contains API credentials or environment specific settings.

For example, credentials for mysql/redis/s3/etc is different between local and production environment.

Enter your local environment variables in .env like this

S3_KEY=mykey
S3_SECRET=mysecret

Enter your production environment variables using heroku command as such

$ heroku config:add S3_KEY=superkey
$ heroku config:add S3_SECRET=supersecret

Then in your scala code, you can access the respective environment variables as such:

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val s3Key = System.getenv("S3_KEY")

Better way to run your app locally

You could use .env in your local development workspace as described in the above sections.

However, it would inefficient to sbt clean compile run and then foreman start everytime you change your code and run.

So the better way is to store directly in your computer’s environment variables.

$ export S3_KEY=mykey

To ensure it’s stored

$ echo $S3_KEY

With that, your could sbt run as per normal.