Add reconcile.ClusterAwareRequest and matching EventHandlers

On-behalf-of: SAP <marvin.beckers@sap.com>
Signed-off-by: Marvin Beckers <marvin@kubermatic.com>

Author: embik

examples/fleet-namespace/cluster.go

@@ -19,27 +19,12 @@ package main
 import (
 	"context"
 
-	"k8s.io/apimachinery/pkg/types"
 	"k8s.io/client-go/tools/record"
 	"sigs.k8s.io/controller-runtime/pkg/cache"
 	"sigs.k8s.io/controller-runtime/pkg/client"
 	"sigs.k8s.io/controller-runtime/pkg/cluster"
-	"sigs.k8s.io/controller-runtime/pkg/reconcile"
 )
 
-type clusterRequest struct {
-	reconcile.Request
-	ClusterName string
-}
-
-// String returns the general purpose string representation.
-func (cr *clusterRequest) String() string {
-	if cr.ClusterName == "" {
-		return cr.NamespacedName.String()
-	}
-	return "cluster://" + cr.ClusterName + string(types.Separator) + cr.NamespacedName.String()
-}
-
 type NamespacedCluster struct {
 	clusterName string
 	cluster.Cluster

examples/fleet-namespace/eventhandler.go

@@ -120,11 +120,11 @@ func main() {
 		os.Exit(1)
 	}
 
-	if err := builder.TypedControllerManagedBy[clusterRequest](mgr).
+	if err := builder.TypedControllerManagedBy[reconcile.ClusterAwareRequest](mgr).
 		Named("fleet-ns-configmap-controller").
-		Watches(&corev1.ConfigMap{}, &EnqueueClusterRequestForObject{}).
-		Complete(reconcile.TypedFunc[clusterRequest](
-			func(ctx context.Context, req clusterRequest) (ctrl.Result, error) {
+		For(&corev1.ConfigMap{}).
+		Complete(reconcile.TypedFunc[reconcile.ClusterAwareRequest](
+			func(ctx context.Context, req reconcile.ClusterAwareRequest) (ctrl.Result, error) {
 				log := log.FromContext(ctx).WithValues("cluster", req.ClusterName)
 
 				cl, err := mgr.GetCluster(ctx, req.ClusterName)

examples/fleet-namespace/main.go

@@ -0,0 +1,9 @@
+# examples/fleet
+
+The `fleet` example is a basic implementation of a multi-cluster-capable controller. As a cluster provider it uses `kind`: Every local kind cluster with a `fleet-` name prefix will be picked up as dynamic cluster if multi-cluster support is enabled in `fleet`.
+
+`fleet` can switch between multi-cluster mode and single-cluster mode via the `--enable-cluster-provider` flag (defaults to `true`) to demonstrate the seamless switch of using the same code base as a "normal" single-cluster controller and as a multi-cluster controller as easy as plugging in a (third-party) cluster provider. To run `fleet` against the current `KUBECONFIG` in single-cluster mode, just run:
+
+```sh
+$ USE_EXISTING_CLUSTER=true go run . --enable-cluster-provider=false
+```