This example shows how to build multiple containers for a multi-module project in both Maven and Gradle.

The project consists of two microservices and a library:

1. name-service - responds with a name
2. shared-library - a project dependency used by name-service
3. hello-service - calls name-service and responds with a greeting

The Maven project is set up with a parent POM (pom.xml) that defines most of the common build configuration. The module POMs (name-service/pom.xml and hello-service/pom.xml) just define inheritance on the parent POM. However, if needed, the module POMs can define custom configuration on jib-maven-plugin specific to that module.

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.

Since dependency module builds happen with the underlying build system (maven/gradle), we must add some extra configuration to ensure that the resulting jar that is built conforms to our reproducibility expectations. The module shared-library uses the Reproducible Build Maven Plugin for maven, and some special Jar properties (preserveFileTimestamps, reproducibleFileOrder) in gradle to achieve this. This configuration can be seen in the shared-library's pom.xml and 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 above.

Set the PROJECT_ID environment variable to your own Google Cloud Platform project:

export PROJECT_ID=$(gcloud config list --format 'value(core.project)')

Run the Maven build:

# build everything
./mvnw package jib:build

# build just hello-service
./mvnw compile jib:build -pl hello-service

# build name-service (with dependency on shared-library)
# you must use "package" for jib to correctly package "shared-library" with the
# "name-service" container
./mvnw package jib:build -pl name-service -am

Run the Gradle build:

# build everything
./gradlew jib

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

# build name-service (with dependency on shared-library)
./gradlew :name-service:jib

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

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

• name-service: gcr.io/PROJECT_ID/name-service:0.1.0
• hello-service: gcr.io/PROJECT_ID/hello-service:0.1.0

kubernetes.yaml defines the manifests for running the two microservices on Kubernetes. Make sure to open the file and change PROJECT_ID to your own Google Cloud Platform project.

Create a Kubernetes cluster:

gcloud container clusters create jib

Apply to your Kubernetes cluster:

kubectl apply -f kubernetes.yaml

Find the EXTERNAL-IP of the hello-service.

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:

Hello Jib Multimodule: A string from 'shared-library'