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✨ Allow webhooks to register custom validators/defaulter types
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This changeset allows our webhook builder to take in a handler any other
struct other than a runtime.Object.

Today having an object as the primary source of truth for both
Defaulting and Validators makes API types carry a lot of information and
business logic alongside their definitions.

Moreover, lots of folks in the past have asked for ways to have an
external type to handle these operations and use a controller runtime
client for validations.

This change brings a new way to register webhooks, which admission.For
handler any type (struct) can be a defaulting or validating handler for
a runtime Object.

Signed-off-by: Vince Prignano <vincepri@vmware.com>
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@vincepri
vincepri committed Sep 28, 2021
1 parent 13f1400 commit 6052973
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Showing 5 changed files with 458 additions and 18 deletions.
78 changes: 60 additions & 18 deletions pkg/builder/webhook.go
View file
Expand Up @@ -17,6 +17,7 @@ limitations under the License.
package builder

import (
"errors"
"net/http"
"net/url"
"strings"
Expand All @@ -32,10 +33,12 @@ import (

// WebhookBuilder builds a Webhook.
type WebhookBuilder struct {
apiType runtime.Object
gvk schema.GroupVersionKind
mgr manager.Manager
config *rest.Config
apiType runtime.Object
withDefaulter admission.CustomDefaulter
withValidator admission.CustomValidator
gvk schema.GroupVersionKind
mgr manager.Manager
config *rest.Config
}

// WebhookManagedBy allows inform its manager.Manager.
Expand All @@ -53,6 +56,18 @@ func (blder *WebhookBuilder) For(apiType runtime.Object) *WebhookBuilder {
return blder
}

// WithDefaulter takes a admission.WithDefaulter interface, a MutatingWebhook will be wired for this type.
func (blder *WebhookBuilder) WithDefaulter(defaulter admission.CustomDefaulter) *WebhookBuilder {
blder.withDefaulter = defaulter
return blder
}

// WithValidator takes a admission.WithValidator interface, a ValidatingWebhook will be wired for this type.
func (blder *WebhookBuilder) WithValidator(validator admission.CustomValidator) *WebhookBuilder {
blder.withValidator = validator
return blder
}

// Complete builds the webhook.
func (blder *WebhookBuilder) Complete() error {
// Set the Config
Expand All @@ -69,9 +84,13 @@ func (blder *WebhookBuilder) loadRestConfig() {
}

func (blder *WebhookBuilder) registerWebhooks() error {
typ, err := blder.getType()
if err != nil {
return err
}

// Create webhook(s) for each type
var err error
blder.gvk, err = apiutil.GVKForObject(blder.apiType, blder.mgr.GetScheme())
blder.gvk, err = apiutil.GVKForObject(typ, blder.mgr.GetScheme())
if err != nil {
return err
}
Expand All @@ -88,12 +107,7 @@ func (blder *WebhookBuilder) registerWebhooks() error {

// registerDefaultingWebhook registers a defaulting webhook if th.
func (blder *WebhookBuilder) registerDefaultingWebhook() {
defaulter, isDefaulter := blder.apiType.(admission.Defaulter)
if !isDefaulter {
log.Info("skip registering a mutating webhook, admission.Defaulter interface is not implemented", "GVK", blder.gvk)
return
}
mwh := admission.DefaultingWebhookFor(defaulter)
mwh := blder.getDefaultingWebhook()
if mwh != nil {
path := generateMutatePath(blder.gvk)

Expand All @@ -108,13 +122,21 @@ func (blder *WebhookBuilder) registerDefaultingWebhook() {
}
}

func (blder *WebhookBuilder) registerValidatingWebhook() {
validator, isValidator := blder.apiType.(admission.Validator)
if !isValidator {
log.Info("skip registering a validating webhook, admission.Validator interface is not implemented", "GVK", blder.gvk)
return
func (blder *WebhookBuilder) getDefaultingWebhook() *admission.Webhook {
if defaulter := blder.withDefaulter; defaulter != nil {
return admission.WithCustomDefaulter(blder.apiType, defaulter)
}
if defaulter, ok := blder.apiType.(admission.Defaulter); ok {
return admission.DefaultingWebhookFor(defaulter)
}
vwh := admission.ValidatingWebhookFor(validator)
log.Info(
"skip registering a mutating webhook, object does not implement admission.Defaulter or WithDefaulter wasn't called",
"GVK", blder.gvk)
return nil
}

func (blder *WebhookBuilder) registerValidatingWebhook() {
vwh := blder.getValidatingWebhook()
if vwh != nil {
path := generateValidatePath(blder.gvk)

Expand All @@ -129,6 +151,19 @@ func (blder *WebhookBuilder) registerValidatingWebhook() {
}
}

func (blder *WebhookBuilder) getValidatingWebhook() *admission.Webhook {
if validator := blder.withValidator; validator != nil {
return admission.WithCustomValidator(blder.apiType, validator)
}
if validator, ok := blder.apiType.(admission.Validator); ok {
return admission.ValidatingWebhookFor(validator)
}
log.Info(
"skip registering a validating webhook, object does not implement admission.Validator or WithValidator wasn't called",
"GVK", blder.gvk)
return nil
}

func (blder *WebhookBuilder) registerConversionWebhook() error {
ok, err := conversion.IsConvertible(blder.mgr.GetScheme(), blder.apiType)
if err != nil {
Expand All @@ -145,6 +180,13 @@ func (blder *WebhookBuilder) registerConversionWebhook() error {
return nil
}

func (blder *WebhookBuilder) getType() (runtime.Object, error) {
if blder.apiType != nil {
return blder.apiType, nil
}
return nil, errors.New("For() must be called with a valid object")
}

func (blder *WebhookBuilder) isAlreadyHandled(path string) bool {
if blder.mgr.GetWebhookServer().WebhookMux == nil {
return false
Expand Down
199 changes: 199 additions & 0 deletions pkg/builder/webhook_test.go
View file
Expand Up @@ -134,6 +134,81 @@ func runTests(admissionReviewVersion string) {
ExpectWithOffset(1, w.Code).To(Equal(http.StatusNotFound))
})

It("should scaffold a defaulting webhook with a custom defaulter", func() {
By("creating a controller manager")
m, err := manager.New(cfg, manager.Options{})
ExpectWithOffset(1, err).NotTo(HaveOccurred())

By("registering the type in the Scheme")
builder := scheme.Builder{GroupVersion: testDefaulterGVK.GroupVersion()}
builder.Register(&TestDefaulter{}, &TestDefaulterList{})
err = builder.AddToScheme(m.GetScheme())
ExpectWithOffset(1, err).NotTo(HaveOccurred())

err = WebhookManagedBy(m).
WithDefaulter(&TestCustomDefaulter{}).
For(&TestDefaulter{}).
Complete()
ExpectWithOffset(1, err).NotTo(HaveOccurred())
svr := m.GetWebhookServer()
ExpectWithOffset(1, svr).NotTo(BeNil())

reader := strings.NewReader(`{
"kind":"AdmissionReview",
"apiVersion":"admission.k8s.io/` + admissionReviewVersion + `",
"request":{
"uid":"07e52e8d-4513-11e9-a716-42010a800270",
"kind":{
"group":"",
"version":"v1",
"kind":"TestDefaulter"
},
"resource":{
"group":"",
"version":"v1",
"resource":"testdefaulter"
},
"namespace":"default",
"operation":"CREATE",
"object":{
"replica":1
},
"oldObject":null
}
}`)

ctx, cancel := context.WithCancel(context.Background())
cancel()
// TODO: we may want to improve it to make it be able to inject dependencies,
// but not always try to load certs and return not found error.
err = svr.Start(ctx)
if err != nil && !os.IsNotExist(err) {
ExpectWithOffset(1, err).NotTo(HaveOccurred())
}

By("sending a request to a mutating webhook path")
path := generateMutatePath(testDefaulterGVK)
req := httptest.NewRequest("POST", "http://svc-name.svc-ns.svc"+path, reader)
req.Header.Add("Content-Type", "application/json")
w := httptest.NewRecorder()
svr.WebhookMux.ServeHTTP(w, req)
ExpectWithOffset(1, w.Code).To(Equal(http.StatusOK))
By("sanity checking the response contains reasonable fields")
ExpectWithOffset(1, w.Body).To(ContainSubstring(`"allowed":true`))
ExpectWithOffset(1, w.Body).To(ContainSubstring(`"patch":`))
ExpectWithOffset(1, w.Body).To(ContainSubstring(`"code":200`))

By("sending a request to a validating webhook path that doesn't exist")
path = generateValidatePath(testDefaulterGVK)
_, err = reader.Seek(0, 0)
ExpectWithOffset(1, err).NotTo(HaveOccurred())
req = httptest.NewRequest("POST", "http://svc-name.svc-ns.svc"+path, reader)
req.Header.Add("Content-Type", "application/json")
w = httptest.NewRecorder()
svr.WebhookMux.ServeHTTP(w, req)
ExpectWithOffset(1, w.Code).To(Equal(http.StatusNotFound))
})

It("should scaffold a validating webhook if the type implements the Validator interface", func() {
By("creating a controller manager")
m, err := manager.New(cfg, manager.Options{})
Expand Down Expand Up @@ -209,6 +284,82 @@ func runTests(admissionReviewVersion string) {
ExpectWithOffset(1, w.Body).To(ContainSubstring(`"code":403`))
})

It("should scaffold a validating webhook with a custom validator", func() {
By("creating a controller manager")
m, err := manager.New(cfg, manager.Options{})
ExpectWithOffset(1, err).NotTo(HaveOccurred())

By("registering the type in the Scheme")
builder := scheme.Builder{GroupVersion: testValidatorGVK.GroupVersion()}
builder.Register(&TestValidator{}, &TestValidatorList{})
err = builder.AddToScheme(m.GetScheme())
ExpectWithOffset(1, err).NotTo(HaveOccurred())

err = WebhookManagedBy(m).
WithValidator(&TestCustomValidator{}).
For(&TestValidator{}).
Complete()
ExpectWithOffset(1, err).NotTo(HaveOccurred())
svr := m.GetWebhookServer()
ExpectWithOffset(1, svr).NotTo(BeNil())

reader := strings.NewReader(`{
"kind":"AdmissionReview",
"apiVersion":"admission.k8s.io/` + admissionReviewVersion + `",
"request":{
"uid":"07e52e8d-4513-11e9-a716-42010a800270",
"kind":{
"group":"",
"version":"v1",
"kind":"TestValidator"
},
"resource":{
"group":"",
"version":"v1",
"resource":"testvalidator"
},
"namespace":"default",
"operation":"UPDATE",
"object":{
"replica":10
},
"oldObject":{
"replica":2
}
}
}`)

ctx, cancel := context.WithCancel(context.Background())
cancel()
// TODO: we may want to improve it to make it be able to inject dependencies,
// but not always try to load certs and return not found error.
err = svr.Start(ctx)
if err != nil && !os.IsNotExist(err) {
ExpectWithOffset(1, err).NotTo(HaveOccurred())
}

By("sending a request to a mutating webhook path that doesn't exist")
path := generateMutatePath(testValidatorGVK)
req := httptest.NewRequest("POST", "http://svc-name.svc-ns.svc"+path, reader)
req.Header.Add("Content-Type", "application/json")
w := httptest.NewRecorder()
svr.WebhookMux.ServeHTTP(w, req)
ExpectWithOffset(1, w.Code).To(Equal(http.StatusNotFound))

By("sending a request to a validating webhook path")
path = generateValidatePath(testValidatorGVK)
_, err = reader.Seek(0, 0)
ExpectWithOffset(1, err).NotTo(HaveOccurred())
req = httptest.NewRequest("POST", "http://svc-name.svc-ns.svc"+path, reader)
req.Header.Add("Content-Type", "application/json")
w = httptest.NewRecorder()
svr.WebhookMux.ServeHTTP(w, req)
ExpectWithOffset(1, w.Code).To(Equal(http.StatusOK))
By("sanity checking the response contains reasonable field")
ExpectWithOffset(1, w.Body).To(ContainSubstring(`"allowed":false`))
ExpectWithOffset(1, w.Body).To(ContainSubstring(`"code":403`))
})

It("should scaffold defaulting and validating webhooks if the type implements both Defaulter and Validator interfaces", func() {
By("creating a controller manager")
m, err := manager.New(cfg, manager.Options{})
Expand Down Expand Up @@ -537,3 +688,51 @@ func (dv *TestDefaultValidator) ValidateDelete() error {
}
return nil
}

// TestCustomDefaulter.

type TestCustomDefaulter struct{}

func (*TestCustomDefaulter) Default(ctx context.Context, obj runtime.Object) error {
d := obj.(*TestDefaulter) //nolint:ifshort
if d.Replica < 2 {
d.Replica = 2
}
return nil
}

var _ admission.CustomDefaulter = &TestCustomDefaulter{}

// TestCustomValidator.

type TestCustomValidator struct{}

func (*TestCustomValidator) ValidateCreate(ctx context.Context, obj runtime.Object) error {
v := obj.(*TestValidator) //nolint:ifshort
if v.Replica < 0 {
return errors.New("number of replica should be greater than or equal to 0")
}
return nil
}

func (*TestCustomValidator) ValidateUpdate(ctx context.Context, oldObj, newObj runtime.Object) error {
v := newObj.(*TestValidator)
old := oldObj.(*TestValidator) //nolint:ifshort
if v.Replica < 0 {
return errors.New("number of replica should be greater than or equal to 0")
}
if v.Replica < old.Replica {
return fmt.Errorf("new replica %v should not be fewer than old replica %v", v.Replica, old.Replica)
}
return nil
}

func (*TestCustomValidator) ValidateDelete(ctx context.Context, obj runtime.Object) error {
v := obj.(*TestValidator) //nolint:ifshort
if v.Replica > 0 {
return errors.New("number of replica should be less than or equal to 0 to delete")
}
return nil
}

var _ admission.CustomValidator = &TestCustomValidator{}

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