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Kubernetes event using the API Server Source

This example shows how to wire Kubernetes cluster events, using the API Server Source, for consumption by a function that has been implemented as a Knative Service.

Before you begin

  1. You must have a Knative cluster running both the Serving and Eventing components. To learn how to install the required components, see Installing Knative.

  2. You can follow the steps below to create new files, or you clone a copy from the repo by running:

    git clone -b "release-0.13" https://github.com/knative/docs knative-docs
    cd knative-docs/docs/eventing/samples/kubernetes-event-source
    

Deployment Steps

Broker

These instructions assume the namespace default, which you can change to your preferred namespace. If you use a different namespace, you will need to modify all the YAML files deployed in this sample to point at that namespace.

  1. Create the default Broker in your namespace:

    kubectl create -f - <<EOF
    apiVersion: eventing.knative.dev/v1
    kind: Broker
    metadata:
     name: default
    EOF
    

Service Account

  1. Create a Service Account that the ApiServerSource runs as. The ApiServerSource watches for Kubernetes events and forwards them to the Knative Eventing Broker. Create a file named serviceaccount.yaml and copy the code block below into it.

    apiVersion: v1
    kind: ServiceAccount
    metadata:
      name: events-sa
      namespace: default
    
    ---
    apiVersion: rbac.authorization.k8s.io/v1
    kind: ClusterRole
    metadata:
      name: event-watcher
    rules:
      - apiGroups:
          - ""
        resources:
          - events
        verbs:
          - get
          - list
          - watch
    
    ---
    apiVersion: rbac.authorization.k8s.io/v1
    kind: ClusterRoleBinding
    metadata:
      name: k8s-ra-event-watcher
    roleRef:
      apiGroup: rbac.authorization.k8s.io
      kind: ClusterRole
      name: event-watcher
    subjects:
      - kind: ServiceAccount
        name: events-sa
        namespace: default
    

    If you want to re-use an existing Service Account with the appropriate permissions, you need to modify the serviceaccount.yaml.

  2. Enter the following command to create the service account from serviceaccount.yaml:

    kubectl apply --filename serviceaccount.yaml
    

Create Event Source for Kubernetes Events

  1. In order to receive events, you have to create a concrete Event Source for a specific namespace. Create a file named k8s-events.yaml and copy the code block below into it.

    apiVersion: sources.knative.dev/v1
    kind: ApiServerSource
    metadata:
      name: testevents
      namespace: default
    spec:
      serviceAccountName: events-sa
      mode: Resource
      resources:
        - apiVersion: v1
          kind: Event
      sink:
        ref:
          apiVersion: eventing.knative.dev/v1
          kind: Broker
          name: default
    

    If you want to consume events from a different namespace or use a different Service Account, you need to modify k8s-events.yaml accordingly.

  2. Enter the following command to create the event source:

    kubectl apply --filename k8s-events.yaml
    

Trigger

In order to check the ApiServerSource is fully working, we will create a simple Knative Service that dumps incoming messages to its log and creates a Trigger from the Broker to that Knative Service.

  1. Create a file named trigger.yaml and copy the code block below into it.

    apiVersion: eventing.knative.dev/v1
    kind: Trigger
    metadata:
      name: testevents-trigger
      namespace: default
    spec:
      broker: default
      subscriber:
        ref:
          apiVersion: serving.knative.dev/v1
          kind: Service
          name: event-display
    
    ---
    # This is a very simple Knative Service that writes the input request to its log.
    
    apiVersion: serving.knative.dev/v1
    kind: Service
    metadata:
      name: event-display
      namespace: default
    spec:
      template:
        spec:
          containers:
            - # This corresponds to
              # https://github.com/knative/eventing-contrib/tree/master/cmd/event_display/main.go
              image: gcr.io/knative-releases/knative.dev/eventing-contrib/cmd/event_display
    
  2. If the deployed ApiServerSource is pointing at a Broker other than default, modify trigger.yaml by adding spec.broker with the Broker’s name.

  3. Deploy trigger.yaml:

    kubectl apply --filename trigger.yaml
    

Create Events

Create events by launching a pod in the default namespace. Create a busybox container and immediately delete it:

kubectl run busybox --image=busybox --restart=Never -- ls
kubectl delete pod busybox

Verify

We will verify that the Kubernetes events were sent into the Knative eventing system by looking at our message dumper function logs. If you deployed the Trigger, continue using this section. If not, you will need to look downstream yourself:

kubectl get pods
kubectl logs -l serving.knative.dev/service=event-display -c user-container

You should see log lines similar to:

☁️  cloudevents.Event
Validation: valid
Context Attributes,
  specversion: 1.0
  type: dev.knative.apiserver.resource.update
  source: https://10.96.0.1:443
  subject: /apis/v1/namespaces/default/events/testevents.15dd3050eb1e6f50
  id: e0447eb7-36b5-443b-9d37-faf4fe5c62f0
  time: 2020-07-28T16:35:14.172979816Z
  datacontenttype: application/json
Extensions,
  kind: Event
  knativearrivaltime: 2020-07-28T16:35:14.173381505Z
  knativehistory: default-kne-trigger-kn-channel.default.svc.cluster.local
  name: busybox.1625f7cfa4cd12f8
  namespace: default
Data,
  {
    "apiVersion": "v1",
    "count": 1,
    "eventTime": null,
    "firstTimestamp": "2020-07-28T16:35:14Z",
    "involvedObject": {
      "apiVersion": "v1",
      "fieldPath": "spec.containers{busybox}",
      "kind": "Pod",
      "name": "busybox",
      "namespace": "default",
      "resourceVersion": "28987493",
      "uid": "1efb342a-737b-11e9-a6c5-42010a8a00ed"
    },
    "kind": "Event",
    "lastTimestamp": "2020-07-28T16:35:14Z",
    "message": "Started container",
    "metadata": {
      "creationTimestamp": "2020-07-28T16:35:14Z",
      "name": "busybox.1625f7cfa4cd12f8",
      "namespace": "default",
      "resourceVersion": "506088",
      "selfLink": "/api/v1/namespaces/default/events/busybox.1625f7cfa4cd12f8",
      "uid": "7f841049-7979-48db-9cbc-93ed2346a1b5",
    },
    "reason": "Started",
    "reportingComponent": "",
    "reportingInstance": "",
    "source": {
      "component": "kubelet",
      "host": "gke-knative-auto-cluster-default-pool-23c23c4f-xdj0"
    },
    "type": "Normal"
  }

Cleanup

You can remove the ServiceAccount, ClusterRoles, ClusterRoleBinding, ApiServerSource, Service and Trigger using:

kubectl --namespace default delete --filename serviceaccount.yaml
kubectl --namespace default delete --filename k8s-events.yaml
kubectl --namespace default delete --filename trigger.yaml