Java-based microservice as an Event Trigger using CloudEvents SDK

Overview

This sample demonstrates how to build and deploy a Java-based microservice as an Event Trigger in SAP BTP, Kyma runtime using CloudEvents SDK.

The sample uses the CloudEvents SDK to deserialize events. Kyma eventing dispatches the CloudEvents to the Spring Boot microservice. The controller uses io.cloudevents:cloudevents-spring to deserialize the event.

You can find further details in the Spring documentation

The order.created event from SAP Commerce Cloud is used as an example of a trigger.

This sample demonstrates how to:

• Set up the development Namespace in the Kyma runtime.
• Configure kubectl to use the KUBECONFIG file downloaded from the Kyma runtime.
• Set up Event Triggers in the Kyma runtime.
• Create and deploy a Spring Boot application to handle the event using the CloudEvents SDK library.
• Configure the Spring Boot application to use the Event Trigger.
• Use kubectl to verify the state.
• Observe the logs using kubectl.

Prerequisites

• SAP BTP, Kyma runtime instance
• Docker
• make
• Gradle
• Kubernetes tooling
• Java 17+
• SAP Commerce Cloud system connected to the Kyma runtime. You can also use the mock. Refer to this blog post to set up the commerce mock.

Steps

Configure Kyma

• Create a new dev Namespace:

• Ensure that the events are configured for the connected application.

  • Navigate to Integration -> Applications:

  • Select the SAP Commerce Cloud system:

  • Ensure that the SAP Commerce Cloud Events are a part of the Provided Service and Events.

  • If not, configure the events from the SAP Commerce Cloud Backoffice or mock commerce whichever you are using.

Configure the application

Event Trigger is implemented as a Spring Boot application using gradle as a build tool.

• The CloudEvents library is added as a dependency to build.gradle.

implementation('io.cloudevents:cloudevents-spring:2.3.0')

• A Plain Old Java Object (POJO) is defined for the order.created event. The POJO reflects the order.created event definition.

• The controller logic unmarshalls the event payload using the CloudEvent SDK APIs.

Prepare for deployment

• Configure the KUBECONFIG file:

  • Set kubectl to use the KUBECONFIG file:

    export KUBECONFIG={path-to-kubeconfig}
    

• Build and push the image to the Docker repository:

  DOCKER_ACCOUNT={your-docker-account} make push-image
  

• Update the image name in the Kubernetes Deployment. Refer to the standard Kubernetes Deployment and Service definitions.

Kubernetes Deployment

This section details out deploying the application and event trigger as standard Kubernetes resources.

To deploy as Helm chart, please refer to Helm Chart Deployment

Deploy the application

• Deploy the application as a Kubernetes Service.

  kubectl -n dev apply -f ./k8s/deployment.yaml
  

• Verify that the Pods are up and running:

  kubectl -n dev get po -l app=sample-event-trigger-java
  

The expected result shows that the Pod for the sample-event-trigger-java Deployment is running:

NAME                                         READY   STATUS    RESTARTS   AGE
sample-event-trigger-java-5fb6856f4d-xk64k   2/2     Running   0          45m

Configure the Event Trigger

• Create the Event Subscription to receive the order.created event from the source. The source is the connected SAP Commerce Cloud system. Update subscription.yaml, Replace {your-connected-commerce-application-name} with your connected commerce application name as shown in Integration -> Applications

kubectl -n dev apply -f ./k8s/subscription.yaml

• Verify that the Subscription is correctly deployed:

kubectl -n dev get subscriptions.eventing.kyma-project.io
NAME                                    READY   AGE
sample-event-trigger-java-subscription  true    10m

Helm Chart Deployment

A Helm Chart definition is also available for developers to try out.

Must Haves

• kubectl
• Helm3

Helm install

To install the helm chart in dev namespace, run

helm install kymaapp ../helm-charts/sample-event-trigger-java --set image.repository=gabbi/sample-event-trigger-java:0.0.2 --set subscription.application={your-connected-application-as-shown-in-kyma} --set subscription.eventType=order.created -n dev

To verify, the installed chart

helm -n dev ls
NAME            NAMESPACE       REVISION        UPDATED                                 STATUS          CHART                           APP VERSION
dev-gateway     dev             1               2020-09-14 17:34:58.607853163 +0000 UTC deployed        gateway-0.0.1
kymaapp         dev             1               2020-09-14 20:20:03.464428 +0200 CEST   deployed        sample-event-trigger-java-0.1.0 1.16.0

Try it out

• Simulate the event from the SAP Solution. For the purpose of this tutorial, use the mock to simulate the order.created event.

  • Go to Remote APIs. It lists all registered APIs and Events.

  • Navigate to SAP Commerce Cloud - Events and send the order.created event.

  • Observe the logs using kubectl:

    kubectl -n dev logs deploy/sample-event-trigger-java -c sample-event-trigger-java
    

    The expected logs look as follows:

    datacontenttype: application/json
    specversion: 1.0
    id: c3603dcf-a401-4cb4-b5cb-d928f65cc1a8
    source: kyma
    time: 2022-02-02T14:51:05.633Z
    type: sap.kyma.custom.mpmockccv2adoptteam2tst2.order.created.v1
    OrderCreated{orderCode='0202-2'}
    

Troubleshooting

Confirm that event is published and compare the naming by looking at the Kyma component eventing-publisher-proxy

kubectl -n kyma-system logs -l app.kubernetes.io/name=eventing-publisher-proxy -c eventing-publisher-proxy

Cleanup

Delete the created resources:

kubectl -n dev delete -f ./k8s/

or, for helm

helm del kymaapp -n dev