WebApp Operator

The WebApp Operator deploys the CustomResourceDefinition for WebApp, then watches and reconciles against instances of WebApps to ensure the desired state meets the actual cluster state.

The WebApp instance represents a Deployment object with confirgurable replicas, a Service, and a ConfigMap that has a index.html file that can be configured to a specific language, and theme. The resources the Operator deploys contain ownerReferences, causing a cascading delete effect when the WebApp instance is deleted.

If any object deployed by the Operator is deleted for any reason, other than through the ownerReference mechanism, the Operator will abruptly redeploy the object.

Demo

Create an ephemeral cluster. (Kind or k3d will work)

Deploy the Operator

kubectl apply -f dist/pepr-module-774fab07-77fa-517c-b5f8-c682c96c20c0.yaml
kubectl wait --for=condition=Ready pods -l app -n pepr-system --timeout=120s

Notice that the WebApp CRD has been deployed

kubectl get crd | grep webapp

Explain the WebApp.spec

kubectl explain wa.spec

# output
GROUP:      pepr.io
KIND:       WebApp
VERSION:    v1alpha1

FIELD: spec <Object>

DESCRIPTION:
    <empty>
FIELDS:
  language      <string> -required-
    Language defines the language of the web application, either English (en) or
    Spanish (es).

  replicas      <integer> -required-
    Replicas is the number of desired replicas.

  theme <string> -required-
    Theme defines the theme of the web application, either dark or light.

Create an instance of a WebApp in English with the light theme and 1 replica

kubectl create ns webapps;
kubectl apply -f -<<EOF
kind: WebApp
apiVersion: pepr.io/v1alpha1
metadata:
  name: webapp-light-en
  namespace: webapps
spec:
  theme: light 
  language: en
  replicas: 1 
EOF

Check that the ConfigMap, Service and Deployment are deployed

kubectl get cm,svc,deploy -n webapps

# output
NAME                                    DATA   AGE
configmap/kube-root-ca.crt              1      6s
configmap/web-content-webapp-light-en   1      5s

NAME                      TYPE        CLUSTER-IP   EXTERNAL-IP   PORT(S)   AGE
service/webapp-light-en   ClusterIP   10.43.85.1   <none>        80/TCP    5s

NAME                              READY   UP-TO-DATE   AVAILABLE   AGE
deployment.apps/webapp-light-en   1/1     1            1           5s

Get the Status of the WebApp

kubectl get wa webapp-light-en -n webapps -ojsonpath="{.status}" | jq  

# output
{
  "observedGeneration": 1,
  "phase": "Ready"
}

Describe the WebApp

kubectl  describe wa webapp-light-en -n webapps

# output
Name:         webapp-light-en
Namespace:    webapps
Labels:       <none>
Annotations:  <none>
API Version:  pepr.io/v1alpha1
Kind:         WebApp
Metadata:
  Creation Timestamp:  2024-04-08T16:02:31Z
  Generation:          1
  Resource Version:    1037
  UID:                 435c3f0a-3002-48ad-a897-c1fe24903c11
Spec:
  Language:  en
  Replicas:  1
  Theme:     light
Status:
  Observed Generation:  1
  Phase:                Ready
Events:
  Type    Reason                    Age   From             Message
  ----    ------                    ----  ----             -------
  Normal  InstanceCreatedOrUpdated  27s   webapp-light-en  Pending
  Normal  InstanceCreatedOrUpdated  27s   webapp-light-en  Ready

Port-forward and look at the WebApp in the browser

kubectl port-forward svc/webapp-light-en -n webapps 3000:80

WebApp

Delete the ConfigMap on the WebApp to watch it the operator reconcile it back

kubectl delete cm -n webapps --all 
# wait a few seconds
kubectl get cm -n webapps 

# output
configmap "kube-root-ca.crt" deleted
configmap "web-content-webapp-light-en" deleted
NAME                          DATA   AGE
kube-root-ca.crt              1      0s
web-content-webapp-light-en   1      0s

Update the WebApp and change the theme to dark and language to spanish

kubectl apply -f -<<EOF
kind: WebApp
apiVersion: pepr.io/v1alpha1
metadata:
  name: webapp-light-en
  namespace: webapps
spec:
  theme: dark 
  language: es
  replicas: 1 
EOF
#output
webapp.pepr.io/webapp-light-en configured

Port-forward and look at the WebApp in the browser

kubectl port-forward svc/webapp-light-en -n webapps 3000:80

WebApp

Delete the WebApp and check the namespace

kubectl delete wa -n webapps --all
# wait a few seconds
kubectl get cm,deploy,svc -n webapps
# output
NAME                         DATA   AGE
configmap/kube-root-ca.crt   1      40s

When the WebApp is deleted, all of the resources that it created are also deleted.