🐛 Correctly handle concurrent updates to ClusterResourceSetBinding

* fix: Correctly handle concurrent updates to ClusterResourceSetBinding

The existing code does not do optimistic locking on the CRSBinding via
`resourceVersion` and hence concurent updates (patches) overwrite each
other, leading to races and inconsistent state of the CRSBinding.

This commit fixes that by forcing optimistic locking via the
controller-runtime client patch options. The downside to this is that
it leads to more reconciles and log output of failed updates, but
this is a much better situation than having inconsistent and inaccurate
state stored in CRSBinding.

* fixup! refactor: Add requested comment re patching spec only

exp/addons/internal/controllers/clusterresourceset_controller.go

@@ -257,7 +257,7 @@ func (r *ClusterResourceSetReconciler) getClustersByClusterResourceSetSelector(c
 // In Reconcile strategy, resources are re-applied to a particular cluster when their definition changes. The hash in ClusterResourceSetBinding is used to check
 // if a resource has changed or not.
 // TODO: If a resource already exists in the cluster but not applied by ClusterResourceSet, the resource will be updated ?
-func (r *ClusterResourceSetReconciler) ApplyClusterResourceSet(ctx context.Context, cluster *clusterv1.Cluster, clusterResourceSet *addonsv1.ClusterResourceSet) error {
+func (r *ClusterResourceSetReconciler) ApplyClusterResourceSet(ctx context.Context, cluster *clusterv1.Cluster, clusterResourceSet *addonsv1.ClusterResourceSet) (rerr error) {
 	log := ctrl.LoggerFrom(ctx, "Cluster", klog.KObj(cluster))
 	ctx = ctrl.LoggerInto(ctx, log)
 
@@ -280,16 +280,14 @@ func (r *ClusterResourceSetReconciler) ApplyClusterResourceSet(ctx context.Conte
 		return err
 	}
 
-	// Initialize the patch helper.
-	patchHelper, err := patch.NewHelper(clusterResourceSetBinding, r.Client)
-	if err != nil {
-		return err
-	}
+	patch := client.MergeFromWithOptions(clusterResourceSetBinding.DeepCopy(), client.MergeFromWithOptimisticLock{})
 
 	defer func() {
 		// Always attempt to Patch the ClusterResourceSetBinding object after each reconciliation.
-		if err := patchHelper.Patch(ctx, clusterResourceSetBinding); err != nil {
-			log.Error(err, "failed to patch config")
+		// Note only the ClusterResourceSetBinding spec will be patched as it does not have a status field, and so
+		// using the patch helper is unnecessary.
+		if err := r.Client.Patch(ctx, clusterResourceSetBinding, patch); err != nil {
+			rerr = kerrors.NewAggregate([]error{rerr, errors.Wrapf(err, "failed to patch ClusterResourceSetBinding %s", klog.KObj(clusterResourceSetBinding))})
 		}
 	}()
 
@@ -300,7 +298,7 @@ func (r *ClusterResourceSetReconciler) ApplyClusterResourceSet(ctx context.Conte
 		Name:       clusterResourceSet.Name,
 		UID:        clusterResourceSet.UID,
 	}))
-	errList := []error{}
+	var errList []error
 	resourceSetBinding := clusterResourceSetBinding.GetOrCreateBinding(clusterResourceSet)
 
 	// Iterate all resources and apply them to the cluster and update the resource status in the ClusterResourceSetBinding object.

exp/addons/internal/controllers/clusterresourceset_controller_test.go

@@ -990,11 +990,56 @@ metadata:
 		g.Expect(env.Patch(ctx, clusterResourceSetInstance, client.MergeFrom(clusterResourceSetInstance.DeepCopy()))).To(Succeed())
 
 		// Wait until ClusterResourceSetBinding is created for the Cluster
-		g.Eventually(func() bool {
+		g.Eventually(func(g Gomega) {
 			binding := &addonsv1.ClusterResourceSetBinding{}
-			err := env.Get(ctx, clusterResourceSetBindingKey, binding)
-			return err == nil
-		}, timeout).Should(BeTrue())
+			g.Expect(env.Get(ctx, clusterResourceSetBindingKey, binding)).Should(Succeed())
+		}, timeout).Should(Succeed())
+	})
+
+	t.Run("Should handle applying multiple ClusterResourceSets concurrently to the same cluster", func(t *testing.T) {
+		g := NewWithT(t)
+		ns := setup(t, g)
+		defer teardown(t, g, ns)
+
+		t.Log("Creating ClusterResourceSet instances that have same labels as selector")
+		for i := 0; i < 10; i++ {
+			clusterResourceSetInstance := &addonsv1.ClusterResourceSet{
+				ObjectMeta: metav1.ObjectMeta{
+					Name:      fmt.Sprintf("clusterresourceset-%s", util.RandomString(6)),
+					Namespace: ns.Name,
+				},
+				Spec: addonsv1.ClusterResourceSetSpec{
+					ClusterSelector: metav1.LabelSelector{
+						MatchLabels: labels,
+					},
+					Resources: []addonsv1.ResourceRef{{Name: configmapName, Kind: "ConfigMap"}, {Name: secretName, Kind: "Secret"}},
+				},
+			}
+			// Create the ClusterResourceSet.
+			g.Expect(env.Create(ctx, clusterResourceSetInstance)).To(Succeed())
+		}
+
+		t.Log("Updating the cluster with labels to trigger cluster resource sets to be applied")
+		testCluster.SetLabels(labels)
+		g.Expect(env.Update(ctx, testCluster)).To(Succeed())
+
+		t.Log("Verifying ClusterResourceSetBinding shows that all CRS have been applied")
+		g.Eventually(func(g Gomega) {
+			clusterResourceSetBindingKey := client.ObjectKey{Namespace: testCluster.Namespace, Name: testCluster.Name}
+			binding := &addonsv1.ClusterResourceSetBinding{}
+			g.Expect(env.Get(ctx, clusterResourceSetBindingKey, binding)).Should(Succeed())
+			g.Expect(binding.Spec.Bindings).To(HaveLen(10))
+			for _, b := range binding.Spec.Bindings {
+				g.Expect(b.Resources).To(HaveLen(2))
+				for _, r := range b.Resources {
+					g.Expect(r.Applied).To(BeTrue())
+				}
+			}
+			g.Expect(binding.OwnerReferences).To(HaveLen(10))
+		}, 4*timeout).Should(Succeed())
+		t.Log("Deleting the created ClusterResourceSet instances")
+		g.Expect(env.DeleteAllOf(ctx, &addonsv1.ClusterResourceSet{}, client.InNamespace(ns.Name))).To(Succeed())
+		g.Expect(env.DeleteAllOf(ctx, &addonsv1.ClusterResourceSetBinding{}, client.InNamespace(ns.Name))).To(Succeed())
 	})
 }
 

exp/addons/internal/controllers/clusterresourceset_helpers.go

@@ -36,6 +36,7 @@ import (
 	"k8s.io/apimachinery/pkg/types"
 	"k8s.io/klog/v2"
 	"sigs.k8s.io/controller-runtime/pkg/client"
+	"sigs.k8s.io/controller-runtime/pkg/controller/controllerutil"
 
 	clusterv1 "sigs.k8s.io/cluster-api/api/v1beta1"
 	addonsv1 "sigs.k8s.io/cluster-api/exp/addons/api/v1beta1"
@@ -108,27 +109,27 @@ func createUnstructured(ctx context.Context, c client.Client, obj *unstructured.
 
 // getOrCreateClusterResourceSetBinding retrieves ClusterResourceSetBinding resource owned by the cluster or create a new one if not found.
 func (r *ClusterResourceSetReconciler) getOrCreateClusterResourceSetBinding(ctx context.Context, cluster *clusterv1.Cluster, clusterResourceSet *addonsv1.ClusterResourceSet) (*addonsv1.ClusterResourceSetBinding, error) {
-	clusterResourceSetBinding := &addonsv1.ClusterResourceSetBinding{}
-	clusterResourceSetBindingKey := client.ObjectKey{
-		Namespace: cluster.Namespace,
-		Name:      cluster.Name,
+	clusterResourceSetBinding := &addonsv1.ClusterResourceSetBinding{
+		ObjectMeta: metav1.ObjectMeta{
+			Name:      cluster.Name,
+			Namespace: cluster.Namespace,
+		},
 	}
+	clusterResourceSetBindingKey := client.ObjectKeyFromObject(clusterResourceSetBinding)
 
 	if err := r.Client.Get(ctx, clusterResourceSetBindingKey, clusterResourceSetBinding); err != nil {
 		if !apierrors.IsNotFound(err) {
 			return nil, err
 		}
-		clusterResourceSetBinding.Name = cluster.Name
-		clusterResourceSetBinding.Namespace = cluster.Namespace
-		clusterResourceSetBinding.OwnerReferences = []metav1.OwnerReference{
-			{
-				APIVersion: addonsv1.GroupVersion.String(),
-				Kind:       "ClusterResourceSet",
-				Name:       clusterResourceSet.Name,
-				UID:        clusterResourceSet.UID,
-			},
+		err = controllerutil.SetOwnerReference(
+			clusterResourceSet,
+			clusterResourceSetBinding,
+			r.Client.Scheme(),
+		)
+		if err != nil {
+			return nil, errors.Wrapf(err, "failed to set owner reference for clusterResourceSetBinding %s for cluster %s/%s", clusterResourceSetBindingKey, cluster.Namespace, cluster.Name)
 		}
-		clusterResourceSetBinding.Spec.Bindings = []*addonsv1.ResourceSetBinding{}
+
 		clusterResourceSetBinding.Spec.ClusterName = cluster.Name
 		if err := r.Client.Create(ctx, clusterResourceSetBinding); err != nil {
 			if apierrors.IsAlreadyExists(err) {

exp/addons/internal/controllers/suite_test.go

@@ -55,13 +55,13 @@ func TestMain(m *testing.M) {
 			Client:  mgr.GetClient(),
 			Tracker: tracker,
 		}
-		if err = reconciler.SetupWithManager(ctx, mgr, controller.Options{MaxConcurrentReconciles: 1}); err != nil {
+		if err = reconciler.SetupWithManager(ctx, mgr, controller.Options{MaxConcurrentReconciles: 10}); err != nil {
 			panic(fmt.Sprintf("Failed to set up cluster resource set reconciler: %v", err))
 		}
 		bindingReconciler := ClusterResourceSetBindingReconciler{
 			Client: mgr.GetClient(),
 		}
-		if err = bindingReconciler.SetupWithManager(ctx, mgr, controller.Options{MaxConcurrentReconciles: 1}); err != nil {
+		if err = bindingReconciler.SetupWithManager(ctx, mgr, controller.Options{MaxConcurrentReconciles: 10}); err != nil {
 			panic(fmt.Sprintf("Failed to set up cluster resource set binding reconciler: %v", err))
 		}
 	}