Discovering Kyma Eventing

In Kyma, you can send and receive events with the help of the Kyma Eventing module processing back end. While providing this, end users don’t have to carry out any protocol or back end by themselves. Therefore, the Eventing moudle aims to make the events’ subscribing and publishing process easier for the users.

When looking at the Kyma Eventing process from beginning to end technology-wise, Kyma Eventing process uses:

• NATS (an open-source messaging system),
• NATS JetStream (provides the back end),
• HTTP-post requests (HTTP requests are delivered via POST-requests in terms of sending and receiving the events),
• Subscription Custom Resources (CR) (which abstracts the creation of different Kubernetes primitives).

Now the question is, how does the actual process of Kyma Eventing look like? First of all, it is important to mention, that Kyma Eventing is based on the Pub/Sub messaging pattern. This means that messages which are triggered in Kyma Eventing, are not sent to subscribers on a direct path but instead are published to a messaging back end, where they are processed, filtered and then sent to subscribers.

Understanding this process is important when using the SAP BTP, Kyma runtime to run your extensions, which should be executed when a certain event gets emitted. For example, the SAP SuccessFactors systems publish the event that a new hire joined the company. The extension can subscribe to the event and can be used to carry out further actions with this data. For example to enroll the new hire to an onboarding session.

While having the delivery and processing flow of Kyma in mind, the Eventing module can be used within the SAP BTP framework for two scenarios:

1. When Business Events are consumed from connected SAP & Non-SAP Solutions:
   Note

   Only CX solutions support Kyma Eventing, for example: SAP Commerce Cloud, SAP Sales Cloud, FSM. Other solutions like SAP S/4HANA currently do not send events via Kyma Eventing, as they send them directly to event mesh from where one needs to set up a webhook. For further information on this, please visit this page.
   
2. When In-Cluster Events are used for event-driven microservices:

In the Kyma dashboard, you can view and update the subscriptions for a specific workload, or you can do it on a namespace-level under Configuration.