PingSource

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

   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

3. Create a PingSource that sends an event containing {"message": "Hello world!"} every minute, by entering the command:

   • YAML
   • kn

   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

4. 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

5. View the logs for the event-display event consumer by entering the following command:

   • kubectl
   • kail

   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

6. 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

7. Optional: You can also delete the PingSource instance only by entering the following command:

   • kubectl
   • kn
   • kubectl: binary data PingSource
   • kn: binary data PingSource

   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

8. Optional: Delete the event-display service:

   • kubectl
   • kn

   kubectl delete service.serving.knative.dev event-display

   kn service delete event-display