Horizon Galaxy

Horizon component for processing published events and performing demultiplexing and filtering tasks.

Prerequisites • Building Galaxy • Configuration • Running Galaxy

Overview

Horizon Galaxy is a crucial component within the Horizon architecture, designed to efficiently multiplex published event messages for each subscription on the respective event type. It plays a key role in managing the flow of events, ensuring duplicates are handled appropriately, and transforming them based on defined response filters.

Note: Galaxy is an essential part of the Horizon ecosystem. Please refer to documentation of the entire system to get the full picture.

Prerequisites

For the optimal setup, ensure you have:

• A running instance of Kafka
• Access to a Kubernetes cluster on which the Subscription (subscriber.horizon.telekom.de) custom resource definition has been registered

Building Galaxy

Gradle build

./gradlew build

Docker build

The default docker base image is azul/zulu-openjdk-alpine:21-jre. This is customizable via the docker build arg DOCKER_BASE_IMAGE. Please note that the default helm values configure the kafka compression type snappy which requires gcompat to be installed in the resulting image. So either provide a base image with gcompat installed or change/disable the compression type in the helm values.

docker build -t horizon-galaxy:latest --build-arg="DOCKER_BASE_IMAGE=<myjvmbaseimage:1.0.0>" . 

Multi-stage Docker build

To simplify things, we have also added a mult-stage Dockerfile to the respository, which also handles the Java build of the application in a build container. The resulting image already contains "gcompat", which is necessary for Kafka compression.

docker build -t horizon-galaxy:latest . -f Dockerfile.multi-stage 

Configuration

Horizon Galaxy's configuration is managed through environment variables. Check the complete list of supported environment variables for setup instructions.

Running Galaxy

Locally

Before you can run Galaxy locally you must have a running instance of Kafka. Additionally, you need to have a Kubernetes config at ${user.home}/.kube/config.main that points to the cluster you want to use.

After that you can run Galaxy in a dev mode using this command:

./gradlew bootRun

To start a kafka instance locally you can run the Docker compose file living in the root of this repository:

docker-compuse up -d

Operational Information

GalaxyService uses an exit code of -2 to shut down the application when the Kafka consumer container stops listening to new Kafka messages.

Local Integration Test with Tracing

Horizon Galaxy includes integration tests that run against an embedded Kafka. To enable local tracing, follow these steps:

1. Spin up Jaeger within Docker using docker-compose-tracing.yaml
2. Set spring.zipkin.enabled to true in the dynamicProperties() method of AbstractIntegrationTest.java

Documentation

Read more about the software architecture and the general process flow of Horizon Galaxy in docs/architecture.md.

Contributing

We're committed to open source, so we welcome and encourage everyone to join its developer community and contribute, whether it's through code or feedback.
By participating in this project, you agree to abide by its Code of Conduct at all times.

Code of Conduct

This project has adopted the Contributor Covenant in version 2.1 as our code of conduct. Please see the details in our CODE_OF_CONDUCT.md. All contributors must abide by the code of conduct.

Licensing

This project follows the REUSE standard for software licensing. You can find a guide for developers at https://telekom.github.io/reuse-template/.
Each file contains copyright and license information, and license texts can be found in the ./LICENSES folder. For more information visit https://reuse.software/.