Knative triggers

1. Create Knative triggers

You will now create triggers which will invoke the HTTP endpoint of Knative services depending on the CloudEvents headers.

The red box in the diagram below highlights the Knative triggers with filter and its bindings that you will be creating within this section.

Each CloudEvents created will be tagged with specific values in the headers ce-type and ce-source which is then used by the Trigger to route them to the correct service HTTP endpoint

From the the top right corner of the OpenShift console, click on the (+) button and then Import Yaml dropdown option

Copy and paste the following CRD to create the 3 Triggers matching the 3 Knative services

apiVersion: eventing.knative.dev/v1
kind: Trigger
metadata:
  name: persist-reviews-trigger
  namespace: globex-serverless-{user_name}
spec:
  broker: globex-broker
  filter:
    attributes:
      source: review-moderated
      type: review-moderated-event
  subscriber:
    ref:
      apiVersion: serving.knative.dev/v1
      kind: Service
      name: persist-reviews
    uri: /review/submit

---
apiVersion: eventing.knative.dev/v1
kind: Trigger
metadata:
  name: moderate-reviews-trigger
  namespace: globex-serverless-{user_name}
spec:
  broker: globex-broker
  filter:
    attributes:
      source: submit-review
      type: submit-review-event
  subscriber:
    ref:
      apiVersion: serving.knative.dev/v1
      kind: Service
      name: aiml-moderate-reviews
    uri: /analyze
---
apiVersion: eventing.knative.dev/v1
kind: Trigger
metadata:
  name: sentiment-reviews-trigger
  namespace: globex-serverless-{user_name}
spec:
  broker: globex-broker
  filter:
    attributes:
      source: submit-review
      type: submit-review-event
  subscriber:
    ref:
      apiVersion: serving.knative.dev/v1
      kind: Service
      name: aiml-sentiment-reviews
    uri: /analyze

You might notice that both the moderate-reviews-trigger and sentiment-reviews-trigger have the same filter attributes. This is because both the corresponding services need to act on the same event (i.e when a review is submitted).

You will note the triggers have been created successfully
Navigate back to the {openshift_cluster_console}/topology/ns/globex-serverless-{user_name}?view=graph[Topology View, window="console"], to view the new triggers you created
Click on the Broker globex-broker to view how the three Knative services subscribe to the KnativeBroker using the Triggers; also note the various filters applied to the triggers.
These filters are the ones which help to match the CloudEvents header of each message to the right service which will act on the message.