Event delivery workflows using brokers and triggers - Event workflows | Serverless applications

Creating a broker
Managing brokers
Filtering events using triggers

Brokers can be used in combination with triggers to deliver events from an event source to an event sink.

Events can be sent from an event source to a broker as an HTTP POST request.

After events have entered the broker, they can be filtered by CloudEvent attributes using triggers, and sent as an HTTP POST request to an event sink.

Creating a broker

OpenShift Serverless provides a default Knative broker that can be created by using the Knative CLI. You can also create the default broker by adding the eventing.knative.dev/injection=enabled label to a namespace if you are a cluster administrator, or by adding the eventing.knative.dev/injection: enabled annotation to a trigger if you are a developer.

Although both developers and cluster administrators can add a broker by injection, only cluster administrators can permanently delete brokers that were created using this method.

Creating a broker using the Knative CLI

Prerequisites

The OpenShift Serverless Operator and Knative Eventing are installed on your OpenShift Container Platform cluster.
You have installed the kn CLI.

Procedure

Create the default broker:
```
$ kn broker create default
```

Verification steps

Use the kn command to list all existing brokers:

$ kn broker list

Example output

NAME      URL                                                                     AGE   CONDITIONS   READY   REASON
default   http://broker-ingress.knative-eventing.svc.cluster.local/test/default   45s   5 OK / 5     True

Optional: If you are using the OpenShift Container Platform web console, you can navigate to the Topology view in the Developer perspective, and observe that the broker exists:

Creating a broker by annotating a trigger

You can create a broker by adding the eventing.knative.dev/injection: enabled annotation to a Trigger object.

If you create a broker by using the eventing.knative.dev/injection: enabled annotation, you cannot delete this broker without cluster administrator permissions. If you delete the broker without having a cluster administrator remove this annotation first, the broker is created again after deletion.

Prerequisites

The OpenShift Serverless Operator and Knative Eventing are installed on your OpenShift Container Platform cluster.

Procedure

Create a Trigger object as a .yaml file that has the eventing.knative.dev/injection: enabled annotation:

apiVersion: eventing.knative.dev/v1
kind: Trigger
metadata:
  annotations:
    eventing.knative.dev/injection: enabled
  name: <trigger-name>
spec:
  broker: default
  subscriber: (1)
    ref:
      apiVersion: serving.knative.dev/v1
      kind: Service
      name: <service-name>

1	Specify details about the event sink, or subscriber, that the trigger sends events to.

Apply the .yaml file:
```
$ oc apply -f <filename>
```

Verification steps

You can verify that the broker has been created successfully by using the oc CLI, or by observing it in the Topology view in the web console.

Use the oc command to get the broker:

$ oc -n <namespace> get broker default

Example output

NAME      READY     REASON    URL                                                                     AGE
default   True                http://broker-ingress.knative-eventing.svc.cluster.local/test/default   3m56s

Navigate to the Topology view in the web console, and observe that the broker exists:

Creating a broker by labeling a namespace

If you have cluster administrator permissions, you can create the default broker automatically by labeling a namespace.

Brokers created using this method will not be removed if you remove the label. You must manually delete them.

Prerequisites

The OpenShift Serverless Operator and Knative Eventing are installed on your OpenShift Container Platform cluster.
You have cluster administrator permissions for OpenShift Container Platform.

Procedure

Label a namespace with eventing.knative.dev/injection=enabled:

$ oc label namespace <namespace> eventing.knative.dev/injection=enabled

Verification steps

You can verify that the broker has been created successfully by using the oc CLI, or by observing it in the Topology view in the web console.

Use the oc command to get the broker:

$ oc -n <namespace> get broker <broker_name>

Example command

$ oc -n default get broker default

Example output

NAME      READY     REASON    URL                                                                     AGE
default   True                http://broker-ingress.knative-eventing.svc.cluster.local/test/default   3m56s

Navigate to the Topology view in the web console, and observe that the broker exists: