Kotlin Multiplatform + Pizza = ❤️

Step 8: Deploy KMP backend on Heroku

The backend works locally and it’s already a big step forward, but how can we deploy it?
We’ll use Heroku for it.
If you don’t have a Heroku account you first need to sign up.
You’ll also need Heroku CLI installed, here are the instructions.

To make sure that the appropriate Java Runtime version is used while deploying on Heroku we need one more configuration . Add file to the root of your project with the following lines:

java.runtime.version=11 = "backend"

After you’ve registered and installed Heroku CLI, you should be able to login from the terminal with the following command:

heroku login

And then create a new application with

heroku create 

You’ll get the id of your newly created app in return, like enigmatic-sands-01782

create heroku app

Then you will need to install a Heroku deploy plugin:

heroku plugins:install heroku-cli-deploy

Now deploy the jar created by shadowJar under the name of our Heroku app with this command. Don’t forget to change the app name.

heroku deploy:jar ./backend/build/libs/Backend.jar --app enigmatic-sands-01782

It’ll take some time to upload the build

create heroku app

After a while you’ll see the upload succeeded:

create heroku app

Finally, add your remote heroku git source:

git remote add heroku 

In the future, every time you make changes you’ll need to update you remote like this:

git push heroku master

Try opening
Don’t forget to replace the Heroku app name with your own.
You’ll see an error.
Try investigating with heroku logs --tail, you’ll find:

Caused by: org.koin.core.error.InstanceCreationException: Could not create
 instance for [Singleton:'com.example.recipecollection.backend.localSource


Caused by: java.lang.IllegalArgumentException: jdbcUrl is required with driverClassName.

It happens because we are missing a postgres database plugin which comes for free with Heroku. Let’s add it with

heroku addons:create heroku-postgresql

You’ll see something like this:

create heroku app

This has created your database url and should have automatically set the JDBC_DATABASE_URL environment variable in heroku. To check it, you can either use

heroku config


heroku run echo \$JDBC_DATABASE_URL

Let’s check out our app again with

heroku open

No errors.
Go to
Awesome, now we can see our application serving pizza from Heroku!