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Using SinkBinding

SinkBinding is used to connect event producers, or event sources, to an event consumer, or event sink, for example, a Knative service or application.

Both of the following procedures require you to create YAML files.

If you change the names of the YAML files from those used in the examples, you must ensure that you also update the corresponding CLI commands.

Using SinkBinding with the Knative CLI (kn)

This guide describes the steps required to create, manage, and delete a SinkBinding instance using kn commands.

Prerequisites

  • You have Knative Serving and Eventing installed.

  • You have the kn CLI installed.

Procedure

  1. To check that SinkBinding is set up correctly, create a Knative event display service, or event sink, that dumps incoming messages to its log:

    $ kn service create event-display --image quay.io/openshift-knative/knative-eventing-sources-event-display:latest

  2. Create a SinkBinding that directs events to the service:

    $ kn source binding create bind-heartbeat --subject Job:batch/v1:app=heartbeat-cron --sink svc:event-display

  3. Create a CronJob.

    1. Create a file named heartbeats-cronjob.yaml and copy the following sample code into it:

      apiVersion: batch/v1beta1
kind: CronJob
metadata:
  name: heartbeat-cron
spec:
spec:
  # Run every minute
  schedule: "* * * * *"
  jobTemplate:
    metadata:
      labels:
        app: heartbeat-cron
    spec:
      template:
        spec:
          restartPolicy: Never
          containers:
            - name: single-heartbeat
              image: quay.io/openshift-knative/knative-eventing-sources-heartbeats:latest
              args:
                - --period=1
              env:
                - name: ONE_SHOT
                  value: "true"
                - name: POD_NAME
                  valueFrom:
                    fieldRef:
                      fieldPath: metadata.name
                - name: POD_NAMESPACE
                  valueFrom:
                    fieldRef:
                      fieldPath: metadata.namespace

    2. After you have created the heartbeats-cronjob.yaml file, apply it by entering:

      $ oc apply --filename heartbeats-cronjob.yaml

  4. Check that the controller is mapped correctly by entering the following command and inspecting the output:

    $ kn source binding describe bind-heartbeat
    Example output
    Name:         bind-heartbeat
Namespace:    demo-2
Annotations:  sources.knative.dev/creator=minikube-user, sources.knative.dev/lastModifier=minikub ...
Age:          2m
Subject:
  Resource:   job (batch/v1)
  Selector:
    app:      heartbeat-cron
Sink:
  Name:       event-display
  Resource:   Service (serving.knative.dev/v1)

Conditions:
  OK TYPE     AGE REASON
  ++ Ready     2m
Verification steps

You can verify that the Kubernetes events were sent to the Knative event sink by looking at the message dumper function logs.

  • View the message dumper function logs by entering the following commands:

    $ oc get pods
    $ oc logs $(oc get pod -o name | grep event-display) -c user-container
    Example output
    ☁️  cloudevents.Event
Validation: valid
Context Attributes,
  specversion: 1.0
  type: dev.knative.eventing.samples.heartbeat
  source: https://knative.dev/eventing-contrib/cmd/heartbeats/#event-test/mypod
  id: 2b72d7bf-c38f-4a98-a433-608fbcdd2596
  time: 2019-10-18T15:23:20.809775386Z
  contenttype: application/json
Extensions,
  beats: true
  heart: yes
  the: 42
Data,
  {
    "id": 1,
    "label": ""
  }

Using SinkBinding with the YAML method

This guide describes the steps required to create, manage, and delete a SinkBinding instance using YAML files.

Prerequisites

  • You have Knative Serving and Eventing installed.

Procedure

  1. To check that SinkBinding is set up correctly, create a Knative event display service, or event sink, that dumps incoming messages to its log.

    1. Copy the following sample YAML into a file named service.yaml:

      apiVersion: serving.knative.dev/v1
kind: Service
metadata:
  name: event-display
spec:
  template:
    spec:
      containers:
        - image: quay.io/openshift-knative/knative-eventing-sources-event-display:latest

    2. After you have created the service.yaml file, apply it by entering:

      $ oc apply -f service.yaml

  2. Create a SinkBinding that directs events to the service.

    1. Create a file named sinkbinding.yaml and copy the following sample code into it:

      apiVersion: sources.knative.dev/v1alpha1
kind: SinkBinding
metadata:
  name: bind-heartbeat
spec:
  subject:
    apiVersion: batch/v1
    kind: Job (1)
    selector:
      matchLabels:
        app: heartbeat-cron

  sink:
    ref:
      apiVersion: serving.knative.dev/v1
      kind: Service
      name: event-display
    1 In this example, any Job with the label app: heartbeat-cron will be bound to the event sink.

    1. After you have created the sinkbinding.yaml file, apply it by entering:

      $ oc apply -f sinkbinding.yaml

  3. Create a CronJob.

    1. Create a file named heartbeats-cronjob.yaml and copy the following sample code into it:

      apiVersion: batch/v1beta1
kind: CronJob
metadata:
  name: heartbeat-cron
spec:
spec:
  # Run every minute
  schedule: "* * * * *"
  jobTemplate:
    metadata:
      labels:
        app: heartbeat-cron
    spec:
      template:
        spec:
          restartPolicy: Never
          containers:
            - name: single-heartbeat
              image: quay.io/openshift-knative/knative-eventing-sources-heartbeats:latest
              args:
                - --period=1
              env:
                - name: ONE_SHOT
                  value: "true"
                - name: POD_NAME
                  valueFrom:
                    fieldRef:
                      fieldPath: metadata.name
                - name: POD_NAMESPACE
                  valueFrom:
                    fieldRef:
                      fieldPath: metadata.namespace

    2. After you have created the heartbeats-cronjob.yaml file, apply it by entering:

      $ oc apply -f heartbeats-cronjob.yaml

  4. Check that the controller is mapped correctly by entering the following command and inspecting the output:

    $ oc get sinkbindings.sources.knative.dev bind-heartbeat -oyaml
    Example output
    spec:
  sink:
    ref:
      apiVersion: serving.knative.dev/v1
      kind: Service
      name: event-display
      namespace: default
  subject:
    apiVersion: batch/v1
    kind: Job
    namespace: default
    selector:
      matchLabels:
        app: heartbeat-cron
Verification steps

You can verify that the Kubernetes events were sent to the Knative event sink by looking at the message dumper function logs.

  1. View the message dumper function logs by entering the following commands:

    $ oc get pods
    $ oc logs $(oc get pod -o name | grep event-display) -c user-container
    Example output
    ☁️  cloudevents.Event
Validation: valid
Context Attributes,
  specversion: 1.0
  type: dev.knative.eventing.samples.heartbeat
  source: https://knative.dev/eventing-contrib/cmd/heartbeats/#event-test/mypod
  id: 2b72d7bf-c38f-4a98-a433-608fbcdd2596
  time: 2019-10-18T15:23:20.809775386Z
  contenttype: application/json
Extensions,
  beats: true
  heart: yes
  the: 42
Data,
  {
    "id": 1,
    "label": ""
  }