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Knative Sample Controller

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Knative servinng events controller defines a controller for knative serving resource and listens for Knative Service events and generates corresponding CloudEvents taking the tektoncd controller as a reference implementation.

Controller architecture

The following roughly defines the controller components:

  1. We register 2 Informers:
  2. A ServingV1/Service reconciler
  3. Embed the CloudEvents SDK client.
  4. We also register a CloudEvents 'receiver' which listens at port 8080.

The following sequence diagram shows the interaction between the components

sequence

Testing and running the controller

  1. Setup a test cluster using KIND with make cluster
  2. Install Knative with make install-knative
  3. Install CRDs with make install-crds
  4. Run the controller with make run-controllers

Scenario 1 - Serving object to CloudEvent

Now create a dummy Knative service

echo "apiVersion: serving.knative.dev/v1
kind: Service
metadata:
  name: hello
spec:
  template:
    spec:
      containers:
      - image: gcr.io/google-samples/hello-app:1.0
" | kubectl apply -f -

We will see the corresponding events received by the controller and subsequently the emitted cloudevent received:

Context Attributes,
  specversion: 1.0
  type: cd.service.deployed.v1      # event of type deployed
  source: default/hello
  id: 1fc4b160-e859-4177-8847-b85c19fdbc18
  time: 2022-01-20T16:56:39.010077Z

On updating the previously created ksvc object, we should see a corresponding event of type upgraded

- - image: gcr.io/google-samples/hello-app:1.0
+ - image: gcr.io/google-samples/hello-app:2.0

This generates the upgraded event and should be reflected in the event as well:

Context Attributes,
  specversion: 1.0
  type: cd.service.upgraded.v1      # event of type upgraded
  source: default/hello
  id: 23225ed1-3dcc-4772-a60d-72ab57bb1ba3
  time: 2022-01-20T17:16:00.253051Z

Scenario 2 - CloudEvent triggering a Knative service creation

  1. Clearing the previous ksvc object
kubectl delete ksvc hello
  1. Trigger a cloud event of type created (cd.service.created.v1) with the following command:
go run cmd/cloudevent/produce.go

This should create a ksvc object in the cluster

note that the event used here (cd.service.created.v1) is not yet defined by the CloudEvents sdk and is just hardcoded for demo purposes.

Check for the created Knative service by running:

kubectl get ksvc

If you are interested in contributing, see CONTRIBUTING.md and DEVELOPMENT.md.