heroku-mvp

Playground project to deploy a sbt-based scala3 server on heroku. I would like to experiment also with sbt-native-image

Local development

Requirements: sbt installed

Run tests and app

To run unit tests

sbt test

To run integration tests

sbt it:test

To run the app through sbt

sbt run

Build fat jar

The project uses sbt-assembly plugin to create a "fat" jar

sbt assembly

The plugin is configured explicitly to run tests on assembly task. The generated jar is heroku-mvp.jar.jar.

The final jar can be run

java -jar target/scala-3.1.0/heroku-mvp.jar.jar

(add other JAVA_OPS if needed)

Docker

Requirements: docker up and running.

For portability, the project is setup to rely directly on Dockerfile instead of using sbt plugins like sbt-docker. In the future, we might explore sbt-native-image

To run docker on MAC OS X, the following can be helpful docker/buildx#426 (comment)

Build final image

Dockerfile contains Docker multi-stage instructions to assembly a lightweight image that only contains the final jar. Intermediate steps are used to fetch sbt and build the jar. The final image is based on jre-slim-buster.

Assuming docker is up and running, the image can be built using

docker build -t <image tag> --build-arg JAVA_VERSION=11 --build-arg SBT_VERSION=1.6.0 -f ./Dockerfile .

Run final image

Once the final image is built, we can run it with

docker run -p 8080:8080 <image tag>

Curl status endpoint

Requirements: curl installed

Regardless of whether the app runs locally through sbt, from a fat jar or through docker, we can check that the service is running fineby using curl to call the healthcheck endpoint:

curl http://localhost:8080/status

// {"status":"ok"}