Custom Resource Definition Assignment

Resource Creation

• For starting minikube $ minikube start --driver podman
• Resource Type = Kluster, Group = ak.dev, version = v1aplha1
• Create resource file Kluster.yaml with Spec details
• Added resource definition by $ kubectl apply -f crd.yaml
• Creating an object of CRD by declaring object.yaml
• Added crd based object by $ kubectl apply -f object.yaml
• Checking if object is running by $ kubeclt get Kluster or $ kubectl get -o wide for more details:

NAME        AGE
kluster-0   51m

• kubectl api-resources | grep Kluster

klusters                          kl           ak.dev/v1alpha1                        true         Kluster

• To check API endpoint $ kubectl proxy --port=8010
• In new terminal $ curl localhost:8010/apis | grep ak.dev/v1alpha1

% Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                 Dload  Upload   Total   Spent    Left  Speed
100  6699    0  6699    0     0   724k      0 --:--:-- --:--:-- --:--:--  817k
          "groupVersion": "ak.dev/v1alpha1",
        "groupVersion": "ak.dev/v1alpha1",

• $ curl localhost:8010/apis/ak.dev/v1alpha1/namespaces/default/klusters for checking object

Controller Creation

• go to $ cd home/{user}/go/src/github.com/{github_username}

• Create folder kluster/pkg/api/{Group}/{version}, add types.go

• Add definitions of cluster type and its fields in the types.go file

• We need to specifiy that the Kluster Spec is a Kubernetes object, for this we will create a register.go file in the same directory that will register the Kluster type to scheme.

• register.go code can be generated using https://github.com/kubernetes/code-generator.

• Create doc.go for declaring tabs. tabs are basically used to call a particular instruction for all valid instance over the codebase. For eg- +k8s:deepcopy-gen=package means that a deep copy must be generated at every package. This is global. If we declare it anywhere else, it will be local.

• Install code-generator by $ go get k8s.io/code-generator (Path: Home/go/pkg/mod/k8s.io/code-generator@v0.26.1)

• Create alias path $ execDir=~/go/pkg/mod/k8s.io/code-generator@v0.26.1

• Create deepcopy, lister, clientset and informers by runnning $ "${execDir}"/generate-groups.sh all github.com/anandxkumar/crd_assignment_2/pkg/client github.com/anandxkumar/crd_assignment_2/pkg/apis run.com:v1alpha1 --go-header-file "${execDir}"/hack/boilerplate.go.txt

• Now the deepcopy, clientset, Informers and listeners would have been added to the locla directory.

• Create the main.go. In main.go we will declare the kubeconfig, create clientsets and the gnerate clusters.

• To add all dependency : $ go mod tidy, then build using $ go build

• To create CRD, you can create it manually or can use controller-gen command i.e. $ go install sigs.k8s.io/kustomize/kustomize@latest and $ controller-gen paths=github.com/anandxkumar/kluster/pkg/apis/ak.dev/v1alpha1 crd:trivialVersions=true rbac:roleName=controller-perms output:crd:artifacts:config=config/crd/bases

• To run main.go $ ./kluster

• To Fix client/listers/kluster.go resource error, go create a function in pkg/apis/ak.dev/v1alpha1/register.go

func Resource(resource string) schema.GroupResource {
	return SchemeGroupVersion.WithResource(resource).GroupResource()
}

Running Controller

• $ go build && ./kluster or $ go run main.go
• In home directory there is a object.yaml, it will create, update or delete the Custom Resource of the CRD we created. Following are the things we can do with the object:
• If we want to create a new object, we can specify the name of CR and count of the number of pods of the CR and run $ kubectl create -f objects.yaml. That number of pods will get running up for that CR.
• If we want to update the number of pods or message, just make the changes in the objects.yaml file and then run $ kubectl apply -f objects.yaml. Depending on the current running pods and the desired pods, the required number of pods will get created or deleted accordingly. To check pods $ kubectl get pods and to check content of pods $ kubectl describe kluster

For deleting a CR

• $ kubectl delete -f object.yml, this will make sure all the associated pods are deleted as well.

For deleting a pod

• $ kubectl delete pod {podname} After deleting the pod, they won't spawn back