✨ Add ClusterFilter to ClusterCache Options

controllers/clustercache/cluster_cache.go

@@ -60,13 +60,22 @@ type Options struct {
 	// will never be created.
 	WatchFilterValue string
 
+	// ClusterFilter is a function that can be used to filter which clusters should be handled
+	// by the ClusterCache. If nil, all clusters will be handled. If set, only clusters for which
+	// the filter returns true will be handled.
+	ClusterFilter ClusterFilter
+
 	// Cache are the cache options for the caches that are created per cluster.
 	Cache CacheOptions
 
 	// Client are the client options for the clients that are created per cluster.
 	Client ClientOptions
 }
 
+// ClusterFilter is a function that filters which clusters should be handled by the ClusterCache.
+// It returns true if the cluster should be handled, false otherwise.
+type ClusterFilter func(cluster *clusterv1.Cluster) bool
+
 // CacheOptions are the cache options for the caches that are created per cluster.
 type CacheOptions struct {
 	// SyncPeriod is the sync period of the cache.
@@ -357,6 +366,11 @@ type clusterCache struct {
 
 	// cacheCtxCancel is used during Shutdown to stop caches.
 	cacheCtxCancel context.CancelCauseFunc
+
+	// ClusterFilter is a function that can be used to filter which clusters should be handled
+	// by the ClusterCache. If nil, all clusters will be handled. If set, only clusters for which
+	// the filter returns true will be handled.
+	clusterFilter ClusterFilter
 }
 
 // clusterSource stores the necessary information so we can enqueue reconcile.Requests for reconcilers that
@@ -451,6 +465,15 @@ func (cc *clusterCache) Reconcile(ctx context.Context, req reconcile.Request) (r
 		return ctrl.Result{RequeueAfter: defaultRequeueAfter}, nil
 	}
 
+	// Apply cluster filter if set
+	if cc.clusterFilter != nil && !cc.clusterFilter(cluster) {
+		log.V(6).Info("Cluster filtered out by ClusterFilter, not connecting")
+		accessor.Disconnect(ctx)
+		cc.deleteClusterAccessor(clusterKey)
+		cc.cleanupClusterSourcesForCluster(clusterKey)
+		return ctrl.Result{}, nil
+	}
+
 	// Return if infrastructure is not ready yet to avoid trying to open a connection when it cannot succeed.
 	// Requeue is not needed as there will be a new reconcile.Request when Cluster.status.initialization.infrastructureProvisioned is set.
 	if !ptr.Deref(cluster.Status.Initialization.InfrastructureProvisioned, false) {

controllers/clustercache/cluster_cache_test.go

@@ -57,6 +57,9 @@ func TestReconcile(t *testing.T) {
 		ObjectMeta: metav1.ObjectMeta{
 			Name:      "test-cluster",
 			Namespace: metav1.NamespaceDefault,
+			Labels: map[string]string{
+				"cluster.x-k8s.io/included-in-clustercache-tests": "true",
+			},
 		},
 		Spec: clusterv1.ClusterSpec{
 			ControlPlaneRef: clusterv1.ContractVersionedObjectReference{
@@ -87,6 +90,9 @@ func TestReconcile(t *testing.T) {
 		clusterAccessorConfig: accessorConfig,
 		clusterAccessors:      make(map[client.ObjectKey]*clusterAccessor),
 		cacheCtx:              context.Background(),
+		clusterFilter: func(cluster *clusterv1.Cluster) bool {
+			return (cluster.ObjectMeta.Labels["cluster.x-k8s.io/included-in-clustercache-tests"] == "true")
+		},
 	}
 
 	// Add a Cluster source and start it (queue will be later used to verify the source works correctly)
@@ -110,6 +116,32 @@ func TestReconcile(t *testing.T) {
 	testCluster.Status.Initialization.InfrastructureProvisioned = ptr.To(true)
 	g.Expect(env.Status().Patch(ctx, testCluster, patch)).To(Succeed())
 
+	// Sanity check that the clusterFilter does pick up the testCluster
+	g.Expect(testCluster.ObjectMeta.Labels["cluster.x-k8s.io/included-in-clustercache-tests"]).To(Equal("true"))
+	g.Expect(cc.clusterFilter(testCluster)).To((BeTrue()))
+	// Exclude from clustercache by changing the label
+	patch = client.MergeFrom(testCluster.DeepCopy())
+	testCluster.ObjectMeta.Labels = map[string]string{
+		"cluster.x-k8s.io/included-in-clustercache-tests": "false",
+	}
+	g.Expect(testCluster.ObjectMeta.Labels["cluster.x-k8s.io/included-in-clustercache-tests"]).To(Equal("false"))
+	g.Expect(cc.clusterFilter(testCluster)).To((BeFalse()))
+	g.Expect(env.Status().Patch(ctx, testCluster, patch)).To(Succeed())
+
+	// Reconcile, cluster should be ignored now
+	// => no requeue, no cluster accessor created
+	res, err = cc.Reconcile(ctx, reconcile.Request{NamespacedName: clusterKey})
+	g.Expect(err).ToNot(HaveOccurred())
+	g.Expect(res).To(Equal(ctrl.Result{}))
+	g.Expect(res.IsZero()).To(BeTrue())
+
+	// Put the label back
+	patch = client.MergeFrom(testCluster.DeepCopy())
+	testCluster.ObjectMeta.Labels = map[string]string{
+		"cluster.x-k8s.io/included-in-clustercache-tests": "true",
+	}
+	g.Expect(env.Status().Patch(ctx, testCluster, patch)).To(Succeed())
+
 	// Reconcile, kubeconfig Secret doesn't exist
 	// => accessor.Connect will fail so we expect a retry with ConnectionCreationRetryInterval.
 	res, err = cc.Reconcile(ctx, reconcile.Request{NamespacedName: clusterKey})