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Kubernetes Event Source example shows how to wire kubernetes cluster events for consumption by a function that has been implemented as a Knative Service. The code for the following files can be found in the /kubernetes-event-source/ directory.

Deployment Steps

Prerequisites

  1. Setup Knative Serving.
  2. Setup Knative Eventing.

Broker

  1. Create the default Broker in your namespace. These instructions assume the namespace default, feel free to change to any other namespace you would like to use instead. If you use a different namespace, you will need to modify all the YAML files deployed in this sample to point at that namespace.
kubectl label namespace default knative-eventing-injection=enabled

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.

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.eventing.knative.dev/v1alpha1
kind: ApiServerSource
metadata:
  name: testevents
  namespace: default
spec:
  serviceAccountName: events-sa
  mode: Resource
  resources:
    - apiVersion: v1
      kind: Event
  sink:
    apiVersion: eventing.knative.dev/v1alpha1
    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.

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.

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

apiVersion: eventing.knative.dev/v1alpha1
kind: Trigger
metadata:
  name: testevents-trigger
  namespace: default
spec:
  subscriber:
    ref:
      apiVersion: serving.knative.dev/v1alpha1
      kind: Service
      name: event-display

---
# This is a very simple Knative Service that writes the input request to its log.

apiVersion: serving.knative.dev/v1alpha1
kind: Service
metadata:
  name: event-display
  namespace: default
spec:
  template:
    spec:
      containers:
        - # This corresponds to
          # https://github.com/knative/eventing-contrib/blob/release-0.5/cmd/event_display/main.go
          image: gcr.io/knative-releases/github.com/knative/eventing-sources/cmd/event_display@sha256:bf45b3eb1e7fc4cb63d6a5a6416cf696295484a7662e0cf9ccdf5c080542c21d

  1. If the deployed ApiServerSource is pointing at a Broker other than default, modify trigger.yaml by adding spec.broker with the Broker's name.

  2. 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, then continue using this section. If not, then 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:

☁️  CloudEvent: valid ✅
Context Attributes,
  SpecVersion: 0.2
  Type: dev.knative.apiserver.resource.add
  Source: https://10.39.240.1:443
  ID: 716d4536-3b92-4fbb-98d9-14bfcf94683f
  Time: 2019-05-10T23:27:06.695575294Z
  ContentType: application/json
  Extensions:
    knativehistory: default-broker-b7k2p-channel-z7mqq.default.svc.cluster.local
    subject: /apis/v1/namespaces/default/events/busybox.159d7608e3a3572c
Transport Context,
  URI: /
  Host: auto-event-display.default.svc.cluster.local
  Method: POST
Data,
  {
    "apiVersion": "v1",
    "count": 1,
    "eventTime": null,
    "firstTimestamp": "2019-05-10T23:27:06Z",
    "involvedObject": {
      "apiVersion": "v1",
      "fieldPath": "spec.containers{busybox}",
      "kind": "Pod",
      "name": "busybox",
      "namespace": "default",
      "resourceVersion": "28987493",
      "uid": "1efb342a-737b-11e9-a6c5-42010a8a00ed"
    },
    "kind": "Event",
    "lastTimestamp": "2019-05-10T23:27:06Z",
    "message": "Started container",
    "metadata": {
      "creationTimestamp": "2019-05-10T23:27:06Z",
      "name": "busybox.159d7608e3a3572c",
      "namespace": "default",
      "resourceVersion": "506088",
      "selfLink": "/api/v1/namespaces/default/events/busybox.159d7608e3a3572c",
      "uid": "2005af47-737b-11e9-a6c5-42010a8a00ed"
    },
    "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, ApiSeverSource, Service and Trigger via:

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