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Add a SinkBinding sample. (#2008)
* Add a SinkBinding sample. This is largely derived from the ContainerSource docs, but using SinkBinding and a CronJob. * Fix the eventing-sources reference. * Add licenses
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‎docs/eventing/samples/sinkbinding/README.md‎

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---
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title: "Sink Binding Example"
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linkTitle: "Sink Binding"
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weight: 10
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type: "docs"
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---
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A SinkBinding is responsible for linking together "addressable" Kubernetes
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resources that may receive events (aka the event "sink") with Kubernetes
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resources that embed a PodSpec (as `spec.template.spec`) and want to produce
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events.
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The SinkBinding can be used to author new event sources using any of the
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familiar compute abstractions that Kubernetes makes available (e.g. Deployment,
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Job, DaemonSet, StatefulSet), or Knative abstractions (e.g. Service,
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Configuration).
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## Create a CronJob that uses SinkBinding
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### Prerequisites
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1. Setup [Knative Serving](../../../serving).
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1. Setup [Knative Eventing and Sources](../../../eventing).
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### Prepare the heartbeats image
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Knative [event-contrib](https://github.com/knative/eventing-contrib) has a
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sample of heartbeats event source. You could clone the source codes by
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```
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git clone -b "{{< branch >}}" https://github.com/knative/eventing-contrib.git
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```
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And then build a heartbeats image and publish to your image repo with
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```
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ko publish knative.dev/eventing-contrib/cmd/heartbeats
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```
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**Note**: `ko publish` requires:
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- [`KO_DOCKER_REPO`](https://github.com/knative/serving/blob/master/DEVELOPMENT.md#environment-setup)
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to be set. (e.g. `gcr.io/[gcloud-project]` or `docker.io/<username>`)
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- you to be authenticated with your `KO_DOCKER_REPO`
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### Creating our event sink
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In order to verify our `SinkBinding` is working, we will create an Event Display
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Service that dumps incoming messages to its log.
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```yaml
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apiVersion: serving.knative.dev/v1
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kind: Service
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metadata:
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name: event-display
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spec:
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template:
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spec:
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containers:
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- image: gcr.io/knative-releases/github.com/knative/eventing-contrib/cmd/event_display
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```
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Use following command to create the service from `service.yaml`:
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```shell
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kubectl apply --filename service.yaml
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```
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The status of the created service can be seen using:
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```shell
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kubectl get ksvc
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NAME URL LATESTCREATED LATESTREADY READY REASON
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event-display http://event-display.default.1.2.3.4.xip.io event-display-gqjbw event-display-gqjbw True
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```
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### Create our SinkBinding
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In order to direct events to our Event Display, we will first create a
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SinkBinding that will inject `$K_SINK` into select `Jobs`:
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```yaml
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apiVersion: sources.eventing.knative.dev/v1alpha1
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kind: SinkBinding
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metadata:
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name: bind-heartbeat
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spec:
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subject:
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apiVersion: batch/v1
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kind: Job
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selector:
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matchLabels:
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app: heartbeat-cron
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sink:
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ref:
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apiVersion: serving.knative.dev/v1
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kind: Service
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name: event-display
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```
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In this case, we will bind any `Job` with the labels `app: heartbeat-cron`.
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Use the following command to create the event source from `sinkbinding.yaml`:
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```shell
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kubectl apply --filename sinkbinding.yaml
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```
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### Create our CronJob
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Now we will use the heartbeats container to send events to `$K_SINK` every time
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the CronJob runs:
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```yaml
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apiVersion: batch/v1beta1
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kind: CronJob
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metadata:
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name: heartbeat-cron
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spec:
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spec:
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# Run every minute
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schedule: "* * * * *"
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jobTemplate:
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metadata:
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labels:
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app: heartbeat-cron
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spec:
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template:
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spec:
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restartPolicy: Never
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containers:
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- name: single-heartbeat
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image: <FILL IN YOUR IMAGE HERE>
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args:
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- --period=1
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env:
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- name: ONE_SHOT
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value: "true"
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- name: POD_NAME
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valueFrom:
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fieldRef:
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fieldPath: metadata.name
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- name: POD_NAMESPACE
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valueFrom:
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fieldRef:
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fieldPath: metadata.namespace
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```
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First, edit `heartbeats-source.yaml` to include the image name from the
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`ko publish` command above, then run the following to apply it:
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```shell
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kubectl apply --filename heartbeats-source.yaml
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```
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### Verify
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We will verify that the message was sent to the Knative eventing system by
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looking at event-display service logs.
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```shell
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kubectl logs -l serving.knative.dev/service=event-display -c user-container --since=10m
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```
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You should see log lines showing the request headers and body of the event
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message sent by the heartbeats source to the display function:
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```
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☁️ cloudevents.Event
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Validation: valid
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Context Attributes,
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specversion: 0.3
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type: dev.knative.eventing.samples.heartbeat
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source: https://knative.dev/eventing-contrib/cmd/heartbeats/#event-test/mypod
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id: 2b72d7bf-c38f-4a98-a433-608fbcdd2596
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time: 2019-10-18T15:23:20.809775386Z
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contenttype: application/json
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Extensions,
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beats: true
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heart: yes
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the: 42
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Data,
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{
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"id": 2,
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"label": ""
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}
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```
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## Using the SinkBinding with a Knative Service
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SinkBinding is also compatible with our Knative Serving Cloud Events
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[samples](../../../serving/samples/cloudevents); as a next step try using those
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together. For example, the [`cloudevents-go`
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sample](../../../serving/samples/cloudevents/cloudevents-go) may be bound with:
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```yaml
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apiVersion: sources.eventing.knative.dev/v1alpha1
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kind: SinkBinding
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metadata:
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name: bind-heartbeat
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spec:
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subject:
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apiVersion: serving.knative.dev/v1
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kind: Service
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name: cloudevents-go
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sink:
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ref:
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apiVersion: serving.knative.dev/v1
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kind: Service
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name: event-display
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```
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‎docs/eventing/samples/sinkbinding/heartbeats-source.yaml‎

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# Copyright 2019 The Knative Authors
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#
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# Licensed under the Apache License, Version 2.0 (the "License");
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# you may not use this file except in compliance with the License.
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# You may obtain a copy of the License at
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#
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# https://www.apache.org/licenses/LICENSE-2.0
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#
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# Unless required by applicable law or agreed to in writing, software
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# distributed under the License is distributed on an "AS IS" BASIS,
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# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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# See the License for the specific language governing permissions and
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# limitations under the License.
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apiVersion: batch/v1beta1
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kind: CronJob
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metadata:
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name: heartbeat-cron
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spec:
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spec:
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# Run every minute
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schedule: "* * * * *"
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jobTemplate:
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metadata:
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labels:
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app: heartbeat-cron
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spec:
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template:
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spec:
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restartPolicy: Never
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containers:
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# This corresponds to a heartbeats image uri you build and publish,
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# e.g. gcr.io/[gcloud-project]/github.com/knative/eventing-contrib/cmd/heartbeats
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- name: single-heartbeat
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image: knative.dev/eventing-contrib/cmd/heartbeats
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args:
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- --period=1
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env:
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- name: ONE_SHOT
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value: "true"
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- name: POD_NAME
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valueFrom:
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fieldRef:
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fieldPath: metadata.name
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- name: POD_NAMESPACE
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valueFrom:
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fieldRef:
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fieldPath: metadata.namespace

‎docs/eventing/samples/sinkbinding/service.yaml‎

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# Copyright 2019 The Knative Authors
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#
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# Licensed under the Apache License, Version 2.0 (the "License");
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# you may not use this file except in compliance with the License.
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# You may obtain a copy of the License at
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#
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# http://www.apache.org/licenses/LICENSE-2.0
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#
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# Unless required by applicable law or agreed to in writing, software
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# distributed under the License is distributed on an "AS IS" BASIS,
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# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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# See the License for the specific language governing permissions and
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# limitations under the License.
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apiVersion: serving.knative.dev/v1
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kind: Service
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metadata:
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name: event-display
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spec:
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template:
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spec:
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containers:
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- image: gcr.io/knative-releases/github.com/knative/eventing-contrib/cmd/event_display

‎docs/eventing/samples/sinkbinding/sinkbinding.yaml‎

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# Copyright 2019 The Knative Authors
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#
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# Licensed under the Apache License, Version 2.0 (the "License");
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# you may not use this file except in compliance with the License.
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# You may obtain a copy of the License at
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#
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# https://www.apache.org/licenses/LICENSE-2.0
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#
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# Unless required by applicable law or agreed to in writing, software
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# distributed under the License is distributed on an "AS IS" BASIS,
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# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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# See the License for the specific language governing permissions and
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# limitations under the License.
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apiVersion: sources.eventing.knative.dev/v1alpha1
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kind: SinkBinding
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metadata:
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name: bind-heartbeat
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spec:
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subject:
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apiVersion: batch/v1
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kind: Job
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selector:
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matchLabels:
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app: heartbeat-cron
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sink:
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ref:
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apiVersion: serving.knative.dev/v1
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kind: Service
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name: event-display

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