openshift-docs/modules/serverless-sinkbinding-yaml.adoc

// Module included in the following assemblies:
//
// * /serverless/eventing/event-sources/serverless-custom-event-sources.adoc

:_mod-docs-content-type: PROCEDURE
[id="serverless-sinkbinding-yaml_{context}"]
= Creating a sink binding by using YAML

Creating Knative resources by using YAML files uses a declarative API, which enables you to describe event sources declaratively and in a reproducible manner. To create a sink binding by using YAML, you must create a YAML file that defines an `SinkBinding` object, then apply it by using the `oc apply` command.

.Prerequisites

* The {ServerlessOperatorName}, Knative Serving and Knative Eventing are installed on the cluster.
* Install the OpenShift CLI (`oc`).
* You have created a project or have access to a project with the appropriate roles and permissions to create applications and other workloads in {product-title}.

.Procedure

. 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.

.. Create a service YAML file:
+
.Example service YAML file
[source,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
----
.. Create the service:
+
[source,terminal]
----
$ oc apply -f <filename>
----

. Create a sink binding instance that directs events to the service.

.. Create a sink binding YAML file:
+
.Example service YAML file
[source,yaml]
----
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.

.. Create the sink binding:
+
[source,terminal]
----
$ oc apply -f <filename>
----

. Create a `CronJob` object.

.. Create a cron job YAML file:
+
.Example cron job YAML file
[source,yaml]
----
apiVersion: batch/v1
kind: CronJob
metadata:
  name: heartbeat-cron
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/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
----
+
[IMPORTANT]
====
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` resource, add the following lines to the `Job` resource YAML definition:

[source,yaml]
----
  jobTemplate:
    metadata:
      labels:
        app: heartbeat-cron
        bindings.knative.dev/include: "true"
----

====
+
.. Create the cron job:
+
[source,terminal]
----
$ oc apply -f <filename>
----

. Check that the controller is mapped correctly by entering the following command and inspecting the output:
+
[source,terminal]
----
$ oc get sinkbindings.sources.knative.dev bind-heartbeat -oyaml
----
+
.Example output
[source,yaml]
----
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.

. Enter the command:
+
[source,terminal]
----
$ oc get pods
----

. Enter the command:
+
[source,terminal]
----
$ oc logs $(oc get pod -o name | grep event-display) -c user-container
----
+
.Example output
[source,terminal]
----
☁️  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": ""
  }
----