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Resource-watcher

Background

The project is used for watching on resources of k8s, when anything changed on the watched resource (add, update, delete), the following action will be taken:

  • Send Cloudevent to specific url
  • Create k8s event
  • Trigger actions

The action should be pluginable, user could implements what they want, for example: send mail...

It's k8s native and implements by a k8s controller. In this demo, the trigger action will be scale-in and scale-out the operators.

An issue for knative is opened to discuss if Knative has any plan to manage native Kubernetes resources.

Development Prerequisites

  1. go: The language Tektoncd-pipeline-operator is built in
  2. git: For source control
  3. kubectl: For interacting with your kube cluster
  4. operator-sdk: https://github.com/operator-framework/operator-sdk
  5. ko(https://github.com/google/ko): Build and deploy Go applications on Kubernetes (optional)

Prototype Details

The project implements Controller/reconciler based on operator-sdk and enhance it to use ko as build/deploy tool.

Basic idea

The basic idea is wrapping operator deployment into knative serving resource.

wrapper typical operator to KSVC

Whole process

wrapper typical operator to KSVC

  1. Create CR: ResourceWatcher
apiVersion: tekton.dev/v1alpha1
kind: ResourceWatcher
metadata:
  name: example-resourcewatcher
  namespace: tekton-sources
spec:
  serviceAccountName: "default"
  sink:
    apiVersion: serving.knative.dev/v1
    kind: Service
    name: knative-operator
    namespace: default
  resources:
    - apiVersion: operator.knative.dev/v1alpha1
      kind: KnativeEventing
  namespaces:
    - tekton-sources

means we will watch a specific CR: KnativeEventing, when creation occurred, a cloudevent will be send to slink(this is the wrapper of Operator):

    apiVersion: serving.knative.dev/v1
    kind: Service
    name: knative-operator
    namespace: default

then the pod of the KSVC will be scale from 0 to 1

  1. When ResourceWatcher created, a pod will be created to do the real work.
  2. When target CR is appeared(KnativeEventing),
  3. the worker pod will send cloudenv to KSVC(remember it's actually a wrapper of Operator)

Installation

Prerequists

Install knative serving first.

Install Process

  1. Git clone the repo.
  2. Deploy resource-watcher:
export KO_DOCKER_REPO=docker.io/gyliu
ko apply -f ./deploy

Check if installation succeed by:

[root@symtest11 resource-watcher]# kubectl -n tekton-sources get po
resource-watcher-6bc7c54c65-ctjjq                          1/1     Running   0          28h
  1. Deploy the operator of knative: knative-operator or
kubectl apply -f ./samples/knative-operator.yaml

For demo, we need delete the deployment of knative-operator since we will wrapper the deployment as a ksvc.

kubectl delete deployment knative-operator
  1. Create a ksvc who is actually the deployment we deleted previously
kubectl create -f ./samples/knative-operator-wrapper.yaml
root@gyliu-dev21:~/go/src/github.com/vincent-pli/resource-watcher# kubectl get service.serving.knative.dev
NAME               URL                                                              LATESTCREATED            LATESTREADY          READY   REASON
autoscale-go       http://autoscale-go-default.apps.gyliu-cap.cp.fyre.ibm.com       autoscale-go-00001       autoscale-go-00001   True
knative-operator   http://knative-operator-default.apps.gyliu-cap.cp.fyre.ibm.com   knative-operator-00001                        False   RevisionMissing

Note: we modify the original deployment:

  • Add an extra container to supply a container port for knative serving to proxy the request.
  • Delete original container port: 9090 which is for metrics collect, since the 9090 is a internal port for knative
  • Modify the valueFrom in the env defination to static string.

The ksvc's pod will disppear afterr 60 second by default.

  1. Watching knative-operator's KnativeEventing:
kubectl apply -f ./samples/KnativeEventing_resourcewatcher_cr.yaml

Then check this:

[root@symtest11 resource-watcher]# kubectl -n tekton-sources get po
NAME                                                       READY   STATUS    RESTARTS   AGE
example-resourcewatcher-deploymenthgcfg-6fb66479bb-wgbbd   1/1     Running   0          11h
resource-watcher-6bc7c54c65-ctjjq                          1/1     Running   0          28h
  1. Create a KnativeEventing:
kubectl create -f ./samples/eventing.yaml -n knative-eventing

Then you could see the ksvc(a wrapper knative-operator)'s pod will start up and then the knative-eventing will be installed.