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PingSource

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A PingSource is an event source that produces events with a fixed payload on a specified cron schedule.

The following example shows how you can configure a PingSource as an event source that sends events every minute to a Knative service named event-display that is used as a sink.

Before you begin

  1. To create a PingSource, you must install Knative Eventing. The PingSource event source type is enabled by default when you install Knative Eventing.
  2. Optional: You can use either kubectl or kn commands to create components such as a sink and PingSource.
  3. Optional: You can use either kubectl or kail for logging during the verification step in this procedure.

Procedure

  1. Optional: Create a new namespace called pingsource-example by entering the following command:

    kubectl create namespace pingsource-example
    

    Creating a namespace for the PingSource example allows you to isolate the components created by this demo, so that it is easier for you to view changes and remove components when you are finished.

  2. To verify that the PingSource is working correctly, create an example sink in the pingsource-example namespace that dumps incoming messages to a log, by entering the command:

kubectl -n pingsource-example apply -f - << EOF
apiVersion: apps/v1
kind: Deployment
metadata:
  name: event-display
spec:
  replicas: 1
  selector:
    matchLabels: &labels
      app: event-display
  template:
    metadata:
      labels: *labels
    spec:
      containers:
        - name: event-display
          image: gcr.io/knative-releases/knative.dev/eventing-contrib/cmd/event_display

---

kind: Service
apiVersion: v1
metadata:
  name: event-display
spec:
  selector:
    app: event-display
  ports:
  - protocol: TCP
    port: 80
    targetPort: 8080
EOF


  1. Create a PingSource that sends an event containing {"message": "Hello world!"} every minute, by entering the command:
kubectl create -n pingsource-example -f - <<EOF
apiVersion: sources.knative.dev/v1
kind: PingSource
metadata:
  name: test-ping-source
spec:
  schedule: "*/1 * * * *"
  contentType: "application/json"
  data: '{"message": "Hello world!"}'
  sink:
    ref:
      apiVersion: v1
      kind: Service
      name: event-display
EOF
kn source ping create test-ping-source \
  --namespace pingsource-example \
  --schedule "*/1 * * * *" \
  --data '{"message": "Hello world!"}' \
  --sink http://event-display.pingsource-example.svc.cluster.local


  1. Optional: Create a PingSource that sends binary data.

    If you want to send binary data in an event, this cannot be directly serialized in YAML. However, you can use dataBase64 in place of data in the PingSource spec to carry a data payload that is base64 encoded.

    To create a PingSource that uses base64 encoded data, enter the command:

    kubectl -n pingsource-example apply -f - <<EOF
    apiVersion: sources.knative.dev/v1
    kind: PingSource
    metadata:
      name: test-ping-source-binary
    spec:
      schedule: "*/1 * * * *"
      contentType: "text/plain"
      dataBase64: "ZGF0YQ=="
      sink:
        ref:
          apiVersion: v1
          kind: Service
          name: event-display
    EOF
    
  2. View the logs for the event-display event consumer by entering the following command:

kubectl -n pingsource-example logs -l app=event-display --tail=100
kail -l serving.knative.dev/service=event-display -c user-container --since=10m


This returns the Attributes and Data of the events that the PingSource sent to the event-display service:

☁️  cloudevents.Event
Validation: valid
Context Attributes,
  specversion: 1.0
  type: dev.knative.sources.ping
  source: /apis/v1/namespaces/pingsource-example/pingsources/test-ping-source
  id: 49f04fe2-7708-453d-ae0a-5fbaca9586a8
  time: 2021-03-25T19:41:00.444508332Z
  datacontenttype: application/json
Data,
  {
    "message": "Hello world!"
  }

If you created a PingSource that sends binary data, you will also see output similar to the following:

☁️  cloudevents.Event
Validation: valid
Context Attributes,
  specversion: 1.0
  type: dev.knative.sources.ping
  source: /apis/v1/namespaces/pingsource-example/pingsources/test-ping-source-binary
  id: ddd7bad2-9b6a-42a7-8f9b-b64494a6ce43
  time: 2021-03-25T19:38:00.455013472Z
  datacontenttype: text/plain
Data,
  data
  1. Optional: You can delete the pingsource-example namespace and all related resources from your cluster by entering the following command:

    kubectl delete namespace pingsource-example
    
  2. Optional: You can also delete the PingSource instance only by entering the following command:

kubectl delete pingsources.sources.knative.dev test-ping-source
kn source ping delete test-ping-source
kubectl delete pingsources.sources.knative.dev test-ping-source-binary
kn source ping delete test-ping-source-binary


  1. Optional: Delete the event-display service:
kubectl delete service.serving.knative.dev event-display
kn service delete event-display
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