memcached-operator

My adaptation of the Go Operator Tutorial from the official Operator SDK website

Prerequisites

• Access to a Kubernetes cluster with cert-manager installed
• Go 1.21
• Operator SDK 1.34

If you do not already have a Kubernetes cluster, get started with Kubernetes in no time with kind.

An example of installing cert-manager on a fresh kind cluster using the official Helm chart:

helm repo add jetstack https://charts.jetstack.io
helm repo update
helm -n cert-manager install \
    cert-manager \
    jetstack/cert-manager \
    --version v1.14.4 \
    --set installCRDs=true \
    --create-namespace

Developing

Fork and clone this repository, make it your working directory, then run:

make deploy

This runs the Memcached operator as a Kubernetes Deployment under the namespace memcached-operator-system:

kubectl -n memcached-operator-system get deploy

Sample output:

NAME                                    READY   UP-TO-DATE   AVAILABLE   AGE
memcached-operator-controller-manager   1/1     1            1           8m

Now deploy a sample Memcached custom resource (CR) using the template available under config/samples/cache_v1alpha1_memcached.yaml:

kubectl apply -f config/samples/cache_v1alpha1_memcached.yaml

Observe that the Memcached CR is created along with its associated Deployment and Pods:

kubectl get memcached,deploy,pod

Sample output:

NAME                                                  AGE
memcached.cache.donaldsebleung.com/memcached-sample   37s

NAME                               READY   UP-TO-DATE   AVAILABLE   AGE
deployment.apps/memcached-sample   3/3     3            3           22s

NAME                                   READY   STATUS    RESTARTS   AGE
pod/memcached-sample-df947c465-85rh4   1/1     Running   0          22s
pod/memcached-sample-df947c465-ck4ht   1/1     Running   0          22s
pod/memcached-sample-df947c465-jvzcf   1/1     Running   0          22s

Now edit the Memcached CR with kubectl edit and observe which modifications are allowed / rejected:

1. Increase .spec.size from 3 to 5
2. Decrease .spec.size from 5 to 1
3. Increase .spec.size from 1 to 6
4. Decrease .spec.size from 6 to 0
5. Decrease .spec.size from 1 to -1
6. Edit .spec.containerPort from 11211 to 0
7. Edit .spec.containerPort from 11211 to 33221

To clean up the resources:

kubectl delete -f config/samples/cache_v1alpha1_memcached.yaml
make undeploy

See also

1. Go Operator Tutorial | Operator SDK
2. Admission Webhooks | Operator SDK

License

Apache 2.0