✨ Implement GenerateUpgradePlan handler

test/extension/handlers/upgradeplan/handlers.go

@@ -0,0 +1,92 @@
+/*
+Copyright 2025 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 upgradeplan contains the handlers for the upgrade plan hook.
+//
+// The implementation of the handlers is specifically designed for Cluster API E2E tests use cases.
+// When implementing custom RuntimeExtension, it is only required to expose HandlerFunc with the
+// signature defined in sigs.k8s.io/cluster-api/api/runtime/hooks/v1alpha1.
+package upgradeplan
+
+import (
+	"context"
+	"slices"
+
+	"k8s.io/klog/v2"
+	ctrl "sigs.k8s.io/controller-runtime"
+	"sigs.k8s.io/controller-runtime/pkg/client"
+
+	runtimehooksv1 "sigs.k8s.io/cluster-api/api/runtime/hooks/v1alpha1"
+	"sigs.k8s.io/cluster-api/exp/topology/desiredstate"
+	"sigs.k8s.io/cluster-api/test/infrastructure/kind"
+)
+
+// ExtensionHandlers provides a common struct for the upgrade plan hook handler.
+// NOTE: it is not mandatory to use a ExtensionHandlers in custom RuntimeExtension, what is important
+// is to expose HandlerFunc with the signature defined in sigs.k8s.io/cluster-api/api/runtime/hooks/v1alpha1.
+type ExtensionHandlers struct {
+	client client.Client
+}
+
+// NewExtensionHandlers returns a ExtensionHandlers for the upgrade plan hook handler.
+func NewExtensionHandlers(client client.Client) *ExtensionHandlers {
+	return &ExtensionHandlers{
+		client: client,
+	}
+}
+
+// DoGenerateUpgradePlan implements the HandlerFunc for the GenerateUpgradePlan hook.
+// This hook generates an upgrade plan based on the Kubernetes versions available in the kind mapper, thus allowing E2E tests to control the behavior during tests.
+// NOTE: custom RuntimeExtension, must implement the body of this func according to the specific use case.
+func (m *ExtensionHandlers) DoGenerateUpgradePlan(ctx context.Context, request *runtimehooksv1.GenerateUpgradePlanRequest, response *runtimehooksv1.GenerateUpgradePlanResponse) {
+	log := ctrl.LoggerFrom(ctx).WithValues("Cluster", klog.KObj(&request.Cluster))
+	ctx = ctrl.LoggerInto(ctx, log)
+	log.Info("GenerateUpgradePlan is called")
+
+	// Get the list of Kubernetes versions from the kind mapper.
+	versions := kind.GetKubernetesVersions()
+	if !slices.Contains(versions, request.ToKubernetesVersion) {
+		versions = append(versions, request.ToKubernetesVersion)
+	}
+
+	// Use GetUpgradePlanFromClusterClassVersions to generate the upgrade plan.
+	getUpgradePlan := desiredstate.GetUpgradePlanFromClusterClassVersions(versions)
+
+	// Call the upgrade plan function.
+	controlPlaneUpgrades, workersUpgrades, err := getUpgradePlan(ctx, request.ToKubernetesVersion, request.FromControlPlaneKubernetesVersion, request.FromWorkersKubernetesVersion)
+	if err != nil {
+		response.Status = runtimehooksv1.ResponseStatusFailure
+		response.Message = err.Error()
+		return
+	}
+
+	// Convert the upgrade plans to UpgradeStep format.
+	response.ControlPlaneUpgrades = make([]runtimehooksv1.UpgradeStep, len(controlPlaneUpgrades))
+	for i, version := range controlPlaneUpgrades {
+		response.ControlPlaneUpgrades[i] = runtimehooksv1.UpgradeStep{
+			Version: version,
+		}
+	}
+
+	response.WorkersUpgrades = make([]runtimehooksv1.UpgradeStep, len(workersUpgrades))
+	for i, version := range workersUpgrades {
+		response.WorkersUpgrades[i] = runtimehooksv1.UpgradeStep{
+			Version: version,
+		}
+	}
+
+	response.Status = runtimehooksv1.ResponseStatusSuccess
+}

test/extension/main.go

@@ -53,6 +53,7 @@ import (
 	"sigs.k8s.io/cluster-api/test/extension/handlers/inplaceupdate"
 	"sigs.k8s.io/cluster-api/test/extension/handlers/lifecycle"
 	"sigs.k8s.io/cluster-api/test/extension/handlers/topologymutation"
+	"sigs.k8s.io/cluster-api/test/extension/handlers/upgradeplan"
 	"sigs.k8s.io/cluster-api/util/flags"
 	"sigs.k8s.io/cluster-api/version"
 )
@@ -263,6 +264,7 @@ func main() {
 	setupTopologyMutationHookHandlers(runtimeExtensionWebhookServer)
 	setupLifecycleHookHandlers(mgr, runtimeExtensionWebhookServer)
 	setupInPlaceUpdateHookHandlers(mgr, runtimeExtensionWebhookServer)
+	setupUpgradePlanHookHandlers(mgr, runtimeExtensionWebhookServer)
 
 	// Setup checks, indexes, reconcilers and webhooks.
 	setupChecks(mgr)
@@ -436,6 +438,23 @@ func setupInPlaceUpdateHookHandlers(mgr ctrl.Manager, runtimeExtensionWebhookSer
 	}
 }
 
+// setupUpgradePlanHookHandlers sets up Upgrade Plan Hooks.
+func setupUpgradePlanHookHandlers(mgr ctrl.Manager, runtimeExtensionWebhookServer *server.Server) {
+	// Create the ExtensionHandlers for the upgrade plan hooks
+	// NOTE: it is not mandatory to group all the ExtensionHandlers using a struct, what is important
+	// is to have HandlerFunc with the signature defined in sigs.k8s.io/cluster-api/api/runtime/hooks/v1alpha1.
+	upgradePlanExtensionHandlers := upgradeplan.NewExtensionHandlers(mgr.GetClient())
+
+	if err := runtimeExtensionWebhookServer.AddExtensionHandler(server.ExtensionHandler{
+		Hook:        runtimehooksv1.GenerateUpgradePlan,
+		Name:        "generate-upgrade-plan",
+		HandlerFunc: upgradePlanExtensionHandlers.DoGenerateUpgradePlan,
+	}); err != nil {
+		setupLog.Error(err, "Error adding handler")
+		os.Exit(1)
+	}
+}
+
 func setupChecks(mgr ctrl.Manager) {
 	if err := mgr.AddReadyzCheck("webhook", mgr.GetWebhookServer().StartedChecker()); err != nil {
 		setupLog.Error(err, "Unable to create ready check")