GO operator tutorial

Example Memcached operator based on Go operator tutorial https://sdk.operatorframework.io/docs/building-operators/golang/tutorial/

How it works

This project aims to follow the Kubernetes Operator pattern.

It uses Controllers, which provide a reconcile function responsible for synchronizing resources until the desired state is reached on the cluster.

Getting Started

You’ll need a Kubernetes cluster to run against. You can use KIND to get a local cluster for testing, or run against a remote cluster. Note: Your controller will automatically use the current context in your kubeconfig file (i.e. whatever cluster kubectl cluster-info shows).

Create a dedicated namespace

kubectl create namespace operator

Switch context

# using kubens
kubens operator

# using kubectl
kubectl config set-context --current --namespace=operator

Running locally

NOTE: Make sure that your active is set to operator

# using kubens
$ kubens -c
operator

# using kubectl
$ kubectl config view --minify | grep namespace
    namespace: operator

Install the CRDs into the cluster:

make install

Verify if CRD is created:

$ kubectl get crd
NAME                          CREATED AT
memcacheds.cache.github.com   2023-08-18T11:28:05Z

Run your controller

This will run in the foreground, so switch to a new terminal if you want to leave it running:

make run

NOTE: You can also run this in one step by running: make install run

Modifying the API definitions

If you are editing the API definitions, generate the manifests such as CRs or CRDs using:

make manifests

NOTE: Run make --help for more information on all potential make targets

More information can be found via the Kubebuilder Documentation

Create Memcached CR

kubectl apply -f config/samples/cache_v1alpha1_memcached.yaml

Check operator logs

2023-08-18T14:52:34+02:00	INFO	Creating a new Deployment	{"controller": "memcached", "controllerGroup": "cache.github.com", "controllerKind": "Memcached", "Memcached": {"name":"memcached-sample","namespace":"operator"}, "namespace": "operator", "name": "memcached-sample", "reconcileID": "20046466-8ac8-4488-a0ca-1b4e2f99f7a8", "Deployment.Namespace": "operator", "Deployment.Name": "memcached-sample"}

Cleanup

1. Delete memcached object:

$ kubectl delete -f config/samples/cache_v1alpha1_memcached.yaml
memcached.cache.github.com "memcached-sample" deleted

2. Stop the controller application ctrl+C

3. Delete crd

kubectl delete crd memcacheds.cache.github.com

Running on the cluster

1. Install l Instances of Custom Resources:

kubectl apply -f config/samples/

2. Build and push your image to the location specified by IMG:

make docker-build docker-push IMG=<some-registry>/go-operator-tutorial:tag

3. Deploy the controller to the cluster with the image specified by IMG:

make deploy IMG=<some-registry>/go-operator-tutorial:tag

Uninstall CRDs

To delete the CRDs from the cluster:

make uninstall

Undeploy controller

UnDeploy the controller from the cluster:

make undeploy

Test it out locally

Troubleshooting

Unable to find MEMCACHED_IMAGE environment variable with the image

make run
...
2023-08-18T14:41:50+02:00	ERROR	Reconciler error	{"controller": "memcached", "controllerGroup": "cache.github.com", "controllerKind": "Memcached", "Memcached": {"name":"memcached-sample","namespace":"operator"}, "namespace": "operator", "name": "memcached-sample", "reconcileID": "c1fa0f69-4b37-42ae-a887-6e17e045c873", "error": "Unable to find MEMCACHED_IMAGE environment variable with the image"}

You have to provide image for deployment using MEMCACHED_IMAGE variable.

F.ex.

make MEMCACHED_IMAGE="memcached:1.4.36-alpine"  run

Unable to delete CR

When the following command got stuck:

$ kubectl delete -f config/samples/cache_v1alpha1_memcached.yaml

Edit CR:

$ kubectl edit memcached memcached-sample

Remove sections:

• deletionTimestamp:
• finalizers:

Run delete command again:

$ kubectl delete -f config/samples/cache_v1alpha1_memcached.yaml