implement a delete hook handler

Author: Yuvaraj Kakaraparthi

internal/webhooks/runtime/cluster.go

@@ -0,0 +1,85 @@
+/*
+Copyright 2022 The Kubernetes Authors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package runtime
+
+import (
+	"context"
+	"net/http"
+
+	"github.com/pkg/errors"
+	ctrl "sigs.k8s.io/controller-runtime"
+	"sigs.k8s.io/controller-runtime/pkg/client"
+	"sigs.k8s.io/controller-runtime/pkg/webhook"
+	"sigs.k8s.io/controller-runtime/pkg/webhook/admission"
+
+	clusterv1 "sigs.k8s.io/cluster-api/api/v1beta1"
+	runtimehooksv1 "sigs.k8s.io/cluster-api/exp/runtime/hooks/api/v1alpha1"
+	"sigs.k8s.io/cluster-api/feature"
+	"sigs.k8s.io/cluster-api/internal/hooks"
+	runtimecatalog "sigs.k8s.io/cluster-api/internal/runtime/catalog"
+)
+
+func (w *ClusterDeleteHandler) SetupWebhookWithManager(mgr ctrl.Manager) error {
+	mgr.GetWebhookServer().Register("/delete-hook-cluster-x-k8s-io-v1beta1-cluster", &webhook.Admission{
+		Handler: w,
+	})
+	return nil
+}
+
+// +kubebuilder:webhook:verbs=delete,path=/delete-hook-cluster-x-k8s-io-v1beta1-cluster,mutating=true,failurePolicy=fail,matchPolicy=Equivalent,groups=cluster.x-k8s.io,resources=clusters,versions=v1beta1,name=delete-hook.cluster.x-k8s.io,sideEffects=None,admissionReviewVersions=v1;v1beta1
+
+type ClusterDeleteHandler struct {
+	Client  client.Client
+	decoder *admission.Decoder
+}
+
+// Handle will capture the intent to eventually call the BeforeClusterDelete hook by adding it to the pending hooks list.
+func (w *ClusterDeleteHandler) Handle(ctx context.Context, req admission.Request) admission.Response {
+	// If RuntimeSDK or ClusterTopology feature gate is not enabled then do nothing and simply pass.
+	if !feature.Gates.Enabled(feature.RuntimeSDK) || feature.Gates.Enabled(feature.ClusterTopology) {
+		return admission.Allowed("")
+	}
+
+	cluster := &clusterv1.Cluster{}
+	err := w.decoder.Decode(req, cluster)
+	if err != nil {
+		return admission.Errored(http.StatusBadRequest, errors.Wrapf(err, "failed to decode Cluster resource"))
+	}
+	// If the Cluster is not deleted then there is nothing to do.
+	if cluster.DeletionTimestamp.IsZero() {
+		return admission.Allowed("")
+	}
+
+	// If the Cluster is not a managed topology then there is nothing to do.
+	if cluster.Spec.Topology == nil {
+		return admission.Allowed("")
+	}
+
+	if err := hooks.MarkAsPending(ctx, w.Client, cluster, runtimehooksv1.BeforeClusterDelete); err != nil {
+		return admission.Errored(http.StatusInternalServerError, errors.Wrapf(err, "failed to mark %s hook as pending for Cluster %s/%s", runtimecatalog.HookName(runtimehooksv1.BeforeClusterDelete), cluster.Namespace, cluster.Name))
+	}
+
+	return admission.Allowed("")
+}
+
+// InjectDecoder injects the decoder.
+// ClusterDeleteHandler implements admission.DecoderInjector.
+// A decoder will be automatically injected.
+func (w *ClusterDeleteHandler) InjectDecoder(d *admission.Decoder) error {
+	w.decoder = d
+	return nil
+}

main.go

@@ -520,6 +520,14 @@ func setupWebhooks(mgr ctrl.Manager) {
 		setupLog.Error(err, "unable to create webhook", "webhook", "ExtensionConfig")
 		os.Exit(1)
 	}
+
+	// NOTE: This hook only runs if the RuntimeSDK and ClusterTopology feature gates are both set to true.
+	// This hook only processes clusters with managed topologies.
+	if err := (&runtimewebhooks.ClusterDeleteHandler{
+		Client: mgr.GetClient(),
+	}).SetupWebhookWithManager(mgr); err != nil {
+		setupLog.Error(err, "unable to create webhook", "webhook", "Cluster delete")
+	}
 }
 
 func concurrency(c int) controller.Options {