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Using sink binding

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

Before developers can use sink binding, cluster administrators must label the namespace that will be configured in the SinkBinding object with bindings.knative.dev/include:"true":

$ oc label namespace <namespace> bindings.knative.dev/include=true

Using sink binding with the Knative CLI

This guide describes the steps required to create, manage, and delete a sink binding instance using the kn CLI.

Prerequisites

  • You have Knative Serving and Eventing installed.

  • You have the the kn CLI installed.

The following procedure requires 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.

Before developers can use sink binding, cluster administrators must label the namespace that will be configured in the SinkBinding object with bindings.knative.dev/include:"true":

$ oc label namespace <namespace> bindings.knative.dev/include=true
Procedure

  1. To check that sink binding 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 object that directs events to the service:

    $ kn source binding create bind-heartbeat --subject Job:batch/v1:app=heartbeat-cron --sink ksvc: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
        bindings.knative.dev/include: "true"
    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

      To use sink binding, you must manually add a bindings.knative.dev/include=true label to your Knative resources.

      For example, to add this label to a CronJob object, add the following lines to the Job resource YAML definition:

        jobTemplate:
    metadata:
      labels:
        app: heartbeat-cron
        bindings.knative.dev/include: "true"

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

      $ 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

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:

    $ 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 sink binding with the YAML method

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

Prerequisites

  • You have Knative Serving and Eventing installed.

The following procedure requires 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.

Before developers can use sink binding, cluster administrators must label the namespace that will be configured in the SinkBinding object with bindings.knative.dev/include:"true":

$ oc label namespace <namespace> bindings.knative.dev/include=true
Procedure

  1. To check that sink binding 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:

      $ oc apply -f service.yaml

  2. Create a SinkBinding object 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.

    2. After you have created the sinkbinding.yaml file, apply it:

      $ oc apply -f sinkbinding.yaml

  3. Create a CronJob object.

    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
        bindings.knative.dev/include: "true"
    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

      To use sink binding, you must manually add a bindings.knative.dev/include=true label to your Knative resources.

      For example, to add this label to a cron job instance, add the following lines to the Job resource YAML definition:

        jobTemplate:
    metadata:
      labels:
        app: heartbeat-cron
        bindings.knative.dev/include: "true"

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

      $ 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

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:

    $ 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": ""
  }