Using subscriptions to send events from a channel to a sink - Knative Eventing | Serverless applications

Creating a subscription

Subscriptions deliver events to event sinks from a Channel.

Creating a subscription

You can create a subscription to connect a service or other event sink to a channel.

Knative Eventing is a Technology Preview feature. The InMemoryChannel type is provided for development use only, and should not be used in a production environment.

Prerequisites

You must have a current installation of OpenShift Serverless, including Knative Serving and Eventing, in your OpenShift Container Platform cluster. This can be installed by a cluster administrator.
If you do not have an existing sink that you wish to use, create a service to use as a sink by following the documentation on Creating and managing serverless applications.
You must have a channel to connect your subscription to. See Using channels with Knative Eventing.

Procedure

Create a Subscription object to connect a channel to a service, by creating a YAML file containing the following:

apiVersion: messaging.knative.dev/v1beta1
kind: Subscription
metadata:
  name: my-subscription (1)
  namespace: default
spec:
  channel: (2)
    apiVersion: messaging.knative.dev/v1beta1
    kind: Channel
    name: example-channel
  delivery: (3)
    deadLetterSink:
      ref:
        apiVersion: serving.knative.dev/v1
        kind: service
        name: error-handler
  subscriber: (4)
    ref:
      apiVersion: serving.knative.dev/v1
      kind: service
      name: event-display

1	Name of the subscription.
2	Configuration settings for the channel that the subscription connects to.
3	Configuration settings for event delivery. This tells the subscription what happens to events that cannot be delivered to the subscriber. When this is configured, events that failed to be consumed are sent to the `deadLetterSink`. The event is dropped, no re-delivery of the event is attempted, and an error is logged in the system. The `deadLetterSink` value must be a Destination.
4	Configuration settings for the subscriber. This is the event sink that events are delivered to from the channel.

Apply the YAML file by entering:
```
$ oc apply -f <filename>
```