Example app to read from a given Kafka topic and processing the message. Based on Apache Camel.

1. Create a Cluster with a local registry and Kafka (e.g. via ./hack/create-kind-cluster.sh)
2. Build and deploy the app to the local registry (localhost:5001):

   mvn package
   

3. Apply manifests (and optionally adjust before):

   kubectl apply -f target/kubernetes/kubernetes.yml
   

4. Test if messages get handled/logged:
   1. Produce some Kafka messages in the topic

      kubectl -n kafka run kafka-producer --rm -ti --image=quay.io/strimzi/kafka:0.47.0-kafka-4.0.0 --rm=true --restart=Never -- bin/kafka-console-producer.sh --bootstrap-server my-cluster-kafka-bootstrap:9092 --topic my-topic
      

   2. check the app logs

      kubectl logs -l app.kubernetes.io/name: camel-app
      

It is possible to forward the messages to another Kafka Topic, which can be specified in the KAFKA_SINK_TOPIC_NAME env.

You can scale the app with KEDA to distribute the message processing on multiple instances.

1. Apply the ScaledObject

   kubectl apply -f keda-scaler.yaml
   

2. Produce some load on the Kafka topic

   kubectl -n kafka run kafka-producer --rm -ti --image=quay.io/strimzi/kafka:0.47.0-kafka-4.0.0 --rm=true --restart=Never -- bin/kafka-producer-perf-test.sh --topic my-topic --num-records 100000 --record-size 10 --throughput -1 --producer-props bootstrap.servers=my-cluster-kafka-bootstrap:9092
   

3. Check how the camel-app gets upscaled by KEDA:

   kubectl get po -l app.kubernetes.io/name=camel-app -w