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Using MicroProfile Reactive Messasing Quickstart with Kafka instances in Red Hat OpenShift Streams for Apache Kafka

Table of Contents

Prerequisites

  • Follow the instructions in the article with the following changes:

    • Use a different name for your Kafka instance (instead of samurai-pizza-kafkas). For the rest of this guide, I’ll use the name wildfly-qs-kafkas

    • Name the topic testing (instead of prices)

Stop at the section "Meanwhile, in your Developer Sandbox…​" as we will now use this quickstart for WildFly instead of the Quarkus one.

Configure Reactive Messaging for Managed Kafka (RHOSAK)

The quickstart was originally intended to run with local Kafka server. In order to configure it for RHOSA, we will deploy a config map that provides the config properties required by MicroProfile Reactive Messaging based on the configuration of the Kafka instance.

oc apply -f https://raw.githubusercontent.com/jmesnil/quickstart/rhosak/microprofile-reactive-messaging-kafka/reactive-messaging-properties.yaml

Connecting the application to Kafka

We need to create a ServiceBinding to bind the KafkaConnection (that represents the Kafka instance) in our application.

To do so, follow the step in the article in the section "Connecting the application to Kafka" with the service binding being:

# rhosak-binding.yaml
apiVersion: binding.operators.coreos.com/v1alpha1
kind: ServiceBinding
metadata:
  name: rhosak-binding
spec:
  application:
    group: apps
    name: kafka-app
    resource: deployments
    version: v1

  namingStrategy: rhosak-config-{{ .name }}
  bindAsFiles: true
  services:
  - group: rhoas.redhat.com
    version: v1alpha1
    kind: KafkaConnection
    name: wildfly-qs-kafkas
Note

you must have to change the name of the KafkaConnection to replace wildfly-qs-kafkas with your own name.

Apply this service binding to your OpenShift cluster with:

oc apply -f ./rhosak-binding.yaml

When we deploy our application, this will create a config map bound to the /bindings/rhosak-bindings directory in the application pods.

Build and Deploy the quickstart

The application is built with Bootable Jar. In order to access the properties from the two config maps created above, we need to add a CLI scripts to add them to the microprofile-config-smallrye subsystem when the Bootable Jar is created durin the exection of mvn package:

/subsystem=microprofile-config-smallrye/config-source=reactive-messaging-properties:add(dir={path=/etc/config/reactive-messaging-properties})
/subsystem=microprofile-config-smallrye/config-source=rhosak-binding:add(dir={path=/bindings/rhosak-binding})

The quickstart will be deployed using the Helm Chart for WildFly:

helm repo add wildfly http://docs.wildfly.org/wildfly-charts/
helm install kafka-app -f https://raw.githubusercontent.com/jmesnil/quickstart/rhosak/microprofile-reactive-messaging-kafka/kafka-app.yaml wildfly/wildfly

Once the application is built and deployed, you can see the output of the application by going to the external URL of your application:

$ oc get route kafka-app -o jsonpath="{.spec.host}"
kafka-app-jmesnil1-dev.apps.sandbox-m2.ll9k.p1.openshiftapps.com
Note

The URL of your application will be different and specific to your OpenShift cluster.

If we query repeatedly this endpoint, we see some of the messages that were propaged on the Kafka instance:

$ curl -L $(oc get route kafka-app -o jsonpath="{.spec.host}")
TimedEntry{id=1, time=2021-06-08 12:10:55.577, message='Kafka'}
TimedEntry{id=2, time=2021-06-08 12:11:03.577, message='Hello'}
TimedEntry{id=3, time=2021-06-08 12:11:23.579, message='Hello'}