Skip to content

Latest commit

 

History

History
271 lines (198 loc) · 7.41 KB

STEP01.md

File metadata and controls

271 lines (198 loc) · 7.41 KB
Raw

1. Bootstrap the project

Tag: step-1

1.1 Basic structure

Outside of GOPATH

go mod init mod.example.com
kubebuilder init --domain example.com

1.2 Adding the first version of Frobber

Create your first API object

kubebuilder create api --group frobs --version v1alpha1 --kind Frobber

Following the On compability part we should add a few things to our type

on api/v1alpha1/frobber_types.go

// FrobberSpec defines the desired state of Frobber
type FrobberSpec struct {
	Height int    `json:"height"`
    Param  string `json:"param"`
}

// FrobberStatus defines the observed state of Frobber
type FrobberStatus struct {
	Phase string `json:"phase"`
}

Update manifests and any generated code

make generate
make manifests

Now we can run the controller and check it out. For specifics please check RUNNING

1.3 Adding webhooks

To work with controllers only it is fundamental to add mutation and validation webhooks to implement defaults and validation. This is done by using Admission controllers kubernetes feature.

1.3.1 Scafold webhooks

To scafold all the necessary code for defaulting and validation just run the code below. For the details check this section of the kubebuilder book.

kubebuilder create webhook --group frobs --version v1alpha1 --kind Frobber --defaulting --programmatic-validation

1.3.2 Install certmanager

Kubernetes requires a https server to call its webhooks, currently our deployments does not have any, so we will invoke cert-manager to manage certificates and inject them into our manager.

Install a certmanager in your cluster: Official

or

kubectl apply -f config/cert-manager.v0.16.0.yaml

1.3.2 Enable webhook and certmanager

inside config/default/kustomization.yaml enable all the [WEBHOOK] and [CERTMANAGER] sections. This should result in something like:

bases:
- ../crd
- ../rbac
- ../manager
# [WEBHOOK] To enable webhook, uncomment all the sections with [WEBHOOK] prefix including the one in 
# crd/kustomization.yaml
- ../webhook
# [CERTMANAGER] To enable cert-manager, uncomment all sections with 'CERTMANAGER'. 'WEBHOOK' components are required.
- ../certmanager
# [PROMETHEUS] To enable prometheus monitor, uncomment all sections with 'PROMETHEUS'. 
#- ../prometheus

patchesStrategicMerge:
  # Protect the /metrics endpoint by putting it behind auth.
  # If you want your controller-manager to expose the /metrics
  # endpoint w/o any authn/z, please comment the following line.
- manager_auth_proxy_patch.yaml

# [WEBHOOK] To enable webhook, uncomment all the sections with [WEBHOOK] prefix including the one in 
# crd/kustomization.yaml
- manager_webhook_patch.yaml

# [CERTMANAGER] To enable cert-manager, uncomment all sections with 'CERTMANAGER'.
# Uncomment 'CERTMANAGER' sections in crd/kustomization.yaml to enable the CA injection in the admission webhooks.
# 'CERTMANAGER' needs to be enabled to use ca injection
- webhookcainjection_patch.yaml

# the following config is for teaching kustomize how to do var substitution
vars:
# [CERTMANAGER] To enable cert-manager, uncomment all sections with 'CERTMANAGER' prefix.
- name: CERTIFICATE_NAMESPACE # namespace of the certificate CR
  objref:
    kind: Certificate
    group: cert-manager.io
    version: v1alpha2
    name: serving-cert # this name should match the one in certificate.yaml
  fieldref:
    fieldpath: metadata.namespace
- name: CERTIFICATE_NAME
  objref:
    kind: Certificate
    group: cert-manager.io
    version: v1alpha2
    name: serving-cert # this name should match the one in certificate.yaml
- name: SERVICE_NAMESPACE # namespace of the service
  objref:
    kind: Service
    version: v1
    name: webhook-service
  fieldref:
    fieldpath: metadata.namespace
- name: SERVICE_NAME
  objref:
    kind: Service
    version: v1
    name: webhook-service

1.3.3 Implement default and validation

Although not best practice, for simplicity sake lets change api/v1alpha1/frobber_types.go adding a Validate method that checks that Height should be greater than zero

// Validate basic Frobber validation
func (r *Frobber) Validate() (err error) {
	var errs field.ErrorList
	defer func() {
		err = errs.ToAggregate()
	}()
	if r.Spec.Height <= 0 {
		errs = append(errs, field.Invalid(field.NewPath("spec", "height"), r.Spec.Height, `should have height greater than zero`)
	}
	return
}

In our api/v1alpha1/frobber_webhook.go file implement the following change, which adds default value for spec.param and invoke the Validate method during Create and Update

[...]

// Default implements webhook.Defaulter so a webhook will be registered for the type
func (r *Frobber) Default() {
	frobberlog.Info("default", "name", r.Name)

	if r.Spec.Param == "" {
		r.Spec.Param = "default"
	}
}

[...]


// ValidateCreate implements webhook.Validator so a webhook will be registered for the type
func (r *Frobber) ValidateCreate() error {
	frobberlog.Info("validate create", "name", r.Name)

	return r.Validate()
}

// ValidateUpdate implements webhook.Validator so a webhook will be registered for the type
func (r *Frobber) ValidateUpdate(old runtime.Object) error {
	frobberlog.Info("validate update", "name", r.Name)

	return r.Validate()
}

[...]

1.4 Adding data

Modify your config/samples/frobs_v1alpha1_frobber.yaml to reflect the structure

apiVersion: frobs.danielfbm.github.io/v1alpha1
kind: Frobber
metadata:
  name: frobber-sample
spec:
  # Add fields here
  height: 3
  param: ""

apply

kubectl apply -f config/samples/frobs_v1alpha1_frobber.yaml

check that it is all well, with our "default" for param

kubectl get frobber frobber-sample -o yaml

Implement a basic controller that prints height and param changing controllers/frobber_controller.go's Reconcile function:

[...]

func (r *FrobberReconciler) Reconcile(req ctrl.Request) (ctrl.Result, error) {
	ctx := context.Background()
	log := r.Log.WithValues("frobber", req.NamespacedName)

	frobber := &frobsv1alpha1.Frobber{}
	err := r.Client.Get(ctx, req.NamespacedName, frobber)
	if err != nil {
		err = client.IgnoreNotFound(err)
		return ctrl.Result{}, err
	}
	// your logic here
	log.Info("Print", "height", frobber.Spec.Height, "param", frobber.Spec.Param)

	return ctrl.Result{}, nil
}

[...]

create a second sample as config/samples/frobs_v1alpha1_frobber_invalid.yaml

apiVersion: frobs.danielfbm.github.io/v1alpha1
kind: Frobber
metadata:
  name: frobber-invalid
spec:
  height: 0
  param: "inches"

apply and check if the validation is working as expected

kubectl apply -f config/samples/frobs_v1alpha1_frobber_invalid.yaml

$ Error from server (spec.height: Invalid value: 0: should have height greater than zero): error when creating "config/samples/frobs_v1alpha1_frobber_invalid.yaml": admission webhook "vfrobber.kb.io" denied the request: spec.height: Invalid value: 0: should have height greater than zero

Now we are finally ready to start

Next

Previous Next
README Step 2