Multi-module SpringBoot Docker Application

This example shows to build multiple containers for a multi-module project in Gradle

How the example is setup

The project consists of one microservice and library

1. common - a project dependency used by microservice
2. microservice - responds with a greeting

The Gradle project is set up with a parent build.gradle that sets some common configuration up for all projects, with each sub-project containing its own build.gradle with some custom configuration. settings.gradle defines which modules to include in the overall build.

Reproducibility of dependency module common

Since dependency module builds happen with the underlying build system (gradle), we must add some extra configuration to ensure that the resulting jar that is built conforms to our reproducibility expectations. The module common uses some special Jar properties (preserveFileTimestamps, reproducibleFileOrder) in gradle to achieve this. This configuration can be seen in the common's build.gradle.

Care must be taken when adding custom attributes to a MANIFEST.MF. Attributes whose values change on every build can affect reproducibility even with the modifications outlined aboved.

How to run

Set the SERVER_PORT, MGMT_SERVER_PORT_, SERVER_ADDR environment variables

export $(cat .env | xargs)

Run the Gradle build:

# build everything
./gradlew jibDockerBuild

# build just hello-service
./gradlew :microservice:jib

You can also run ./gradle-build.sh as a shorthand.

Where are the containers

The output of the build should have the container image references highlighted in cyan. You can expect them to be at:

• microservice: demo-ixcc-app

How to run on Kubernetes

kubernetes.yaml defines the manifests for running the microservice on Kubernetes.

Apply to your Kubernetes cluster:

helm install 

Find the EXTERNAL-IP of the ixcc-demo-app.

NAME                TYPE           CLUSTER-IP      EXTERNAL-IP     PORT(S)        AGE
svc/hello-service   LoadBalancer   10.19.243.223   35.237.89.148   80:30196/TCP   1m

Visit the IP in your web browser and you should see:

{"id":1,"content":"Hello, Stranger!"}