✨ Backport release-0.5: Support metadata-only watches

pkg/builder/controller.go

@@ -20,6 +20,7 @@ import (
 	"fmt"
 	"strings"
 
+	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
 	"k8s.io/apimachinery/pkg/runtime"
 	"k8s.io/client-go/rest"
 	"sigs.k8s.io/controller-runtime/pkg/client/apiutil"
@@ -155,20 +156,42 @@ func (blder *Builder) Build(r reconcile.Reconciler) (controller.Controller, erro
 	return blder.ctrl, nil
 }
 
+func (blder *Builder) project(obj runtime.Object) (runtime.Object, error) {
+	switch o := obj.(type) {
+	case *onlyMetadataWrapper:
+		metaObj := &metav1.PartialObjectMetadata{}
+		gvk, err := getGvk(o.Object, blder.mgr.GetScheme())
+		if err != nil {
+			return nil, fmt.Errorf("unable to determine GVK of %T for a metadata-only watch: %w", obj, err)
+		}
+		metaObj.SetGroupVersionKind(gvk)
+		return metaObj, nil
+	default:
+		return obj, nil
+	}
+}
+
 func (blder *Builder) doWatch() error {
 	// Reconcile type
-	src := &source.Kind{Type: blder.apiType}
-	hdler := &handler.EnqueueRequestForObject{}
-	err := blder.ctrl.Watch(src, hdler, blder.predicates...)
+	apiType, err := blder.project(blder.apiType)
 	if err != nil {
 		return err
 	}
+	src := &source.Kind{Type: apiType}
+	hdler := &handler.EnqueueRequestForObject{}
+	if err := blder.ctrl.Watch(src, hdler, blder.predicates...); err != nil {
+		return err
+	}
 
 	// Watches the managed types
 	for _, obj := range blder.managedObjects {
-		src := &source.Kind{Type: obj}
+		typeForSrc, err := blder.project(obj)
+		if err != nil {
+			return err
+		}
+		src := &source.Kind{Type: typeForSrc}
 		hdler := &handler.EnqueueRequestForOwner{
-			OwnerType:    blder.apiType,
+			OwnerType:    apiType,
 			IsController: true,
 		}
 		if err := blder.ctrl.Watch(src, hdler, blder.predicates...); err != nil {
@@ -178,10 +201,17 @@ func (blder *Builder) doWatch() error {
 
 	// Do the watch requests
 	for _, w := range blder.watchRequest {
+		// If the source of this watch is of type *source.Kind, project it.
+		if srckind, ok := w.src.(*source.Kind); ok {
+			typeForSrc, err := blder.project(srckind.Type)
+			if err != nil {
+				return err
+			}
+			srckind.Type = typeForSrc
+		}
 		if err := blder.ctrl.Watch(w.src, w.eventhandler, blder.predicates...); err != nil {
 			return err
 		}
-
 	}
 	return nil
 }
@@ -196,7 +226,11 @@ func (blder *Builder) getControllerName() (string, error) {
 	if blder.name != "" {
 		return blder.name, nil
 	}
-	gvk, err := getGvk(blder.apiType, blder.mgr.GetScheme())
+	obj, err := blder.project(blder.apiType)
+	if err != nil {
+		return "", err
+	}
+	gvk, err := getGvk(obj, blder.mgr.GetScheme())
 	if err != nil {
 		return "", err
 	}

pkg/builder/controller_test.go

@@ -23,6 +23,8 @@ import (
 
 	. "github.com/onsi/ginkgo"
 	. "github.com/onsi/gomega"
+	"k8s.io/client-go/rest"
+	"sigs.k8s.io/controller-runtime/pkg/cache"
 
 	appsv1 "k8s.io/api/apps/v1"
 	corev1 "k8s.io/api/core/v1"
@@ -203,8 +205,107 @@ var _ = Describe("application", func() {
 			close(done)
 		}, 10)
 	})
+
+	Describe("watching with projections", func() {
+		var mgr manager.Manager
+		BeforeEach(func() {
+			// use a cache that intercepts requests for fully typed objects to
+			// ensure we use the projected versions
+			var err error
+			mgr, err = manager.New(cfg, manager.Options{NewCache: newNonTypedOnlyCache})
+			Expect(err).NotTo(HaveOccurred())
+		})
+
+		It("should support watching For, Owns, and Watch as metadata", func() {
+			statefulSetMaps := make(chan *metav1.PartialObjectMetadata)
+
+			bldr := ControllerManagedBy(mgr).
+				For(OnlyMetadata(&appsv1.Deployment{})).
+				Owns(OnlyMetadata(&appsv1.ReplicaSet{})).
+				Watches(&source.Kind{Type: OnlyMetadata(&appsv1.StatefulSet{})},
+					&handler.EnqueueRequestsFromMapFunc{
+						ToRequests: handler.ToRequestsFunc(func(o handler.MapObject) []reconcile.Request {
+							ometa := o.Object.(*metav1.PartialObjectMetadata)
+							statefulSetMaps <- ometa
+							return nil
+						}),
+					})
+
+			doReconcileTest("8", stop, bldr, mgr, true)
+
+			By("Creating a new stateful set")
+			set := &appsv1.StatefulSet{
+				ObjectMeta: metav1.ObjectMeta{
+					Namespace: "default",
+					Name:      "test1",
+					Labels: map[string]string{
+						"foo": "bar",
+					},
+				},
+				Spec: appsv1.StatefulSetSpec{
+					Selector: &metav1.LabelSelector{
+						MatchLabels: map[string]string{"foo": "bar"},
+					},
+					Template: corev1.PodTemplateSpec{
+						ObjectMeta: metav1.ObjectMeta{Labels: map[string]string{"foo": "bar"}},
+						Spec: corev1.PodSpec{
+							Containers: []corev1.Container{
+								{
+									Name:  "nginx",
+									Image: "nginx",
+								},
+							},
+						},
+					},
+				},
+			}
+			err := mgr.GetClient().Create(context.TODO(), set)
+			Expect(err).NotTo(HaveOccurred())
+
+			By("Checking that the mapping function has been called")
+			Eventually(func() bool {
+				metaSet := <-statefulSetMaps
+				Expect(metaSet.Name).To(Equal(set.Name))
+				Expect(metaSet.Namespace).To(Equal(set.Namespace))
+				Expect(metaSet.Labels).To(Equal(set.Labels))
+				return true
+			}).Should(BeTrue())
+		})
+	})
 })
 
+// newNonTypedOnlyCache returns a new cache that wraps the normal cache,
+// returning an error if normal, typed objects have informers requested.
+func newNonTypedOnlyCache(config *rest.Config, opts cache.Options) (cache.Cache, error) {
+	normalCache, err := cache.New(config, opts)
+	if err != nil {
+		return nil, err
+	}
+	return &nonTypedOnlyCache{
+		Cache: normalCache,
+	}, nil
+}
+
+// nonTypedOnlyCache is a cache.Cache that only provides metadata &
+// unstructured informers.
+type nonTypedOnlyCache struct {
+	cache.Cache
+}
+
+func (c *nonTypedOnlyCache) GetInformer(obj runtime.Object) (cache.Informer, error) {
+	switch obj.(type) {
+	case (*metav1.PartialObjectMetadata):
+		return c.Cache.GetInformer(obj)
+	default:
+		return nil, fmt.Errorf("did not want to provide an informer for normal type %T", obj)
+	}
+}
+func (c *nonTypedOnlyCache) GetInformerForKind(gvk schema.GroupVersionKind) (cache.Informer, error) {
+	return nil, fmt.Errorf("don't try to sidestep the restriction on informer types by calling GetInformerForKind")
+}
+
+// TODO(directxman12): this function has too many arguments, and the whole
+// "nameSuffix" think is a bit of a hack It should be cleaned up significantly by someone with a bit of time
 func doReconcileTest(nameSuffix string, stop chan struct{}, blder *Builder, mgr manager.Manager, complete bool) {
 	deployName := "deploy-name-" + nameSuffix
 	rsName := "rs-name-" + nameSuffix
@@ -267,8 +368,8 @@ func doReconcileTest(nameSuffix string, stop chan struct{}, blder *Builder, mgr
 	Expect(err).NotTo(HaveOccurred())
 
 	By("Waiting for the Deployment Reconcile")
-	Expect(<-ch).To(Equal(reconcile.Request{
-		NamespacedName: types.NamespacedName{Namespace: "default", Name: deployName}}))
+	Eventually(ch).Should(Receive(Equal(reconcile.Request{
+		NamespacedName: types.NamespacedName{Namespace: "default", Name: deployName}})))
 
 	By("Creating a ReplicaSet")
 	// Expect a Reconcile when an Owned object is managedObjects.
@@ -297,8 +398,8 @@ func doReconcileTest(nameSuffix string, stop chan struct{}, blder *Builder, mgr
 	Expect(err).NotTo(HaveOccurred())
 
 	By("Waiting for the ReplicaSet Reconcile")
-	Expect(<-ch).To(Equal(reconcile.Request{
-		NamespacedName: types.NamespacedName{Namespace: "default", Name: deployName}}))
+	Eventually(ch).Should(Receive(Equal(reconcile.Request{
+		NamespacedName: types.NamespacedName{Namespace: "default", Name: deployName}})))
 
 }
 

pkg/builder/example_test.go

@@ -21,6 +21,7 @@ import (
 	"fmt"
 	"os"
 
+	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
 	logf "sigs.k8s.io/controller-runtime/pkg/log"
 
 	appsv1 "k8s.io/api/apps/v1"
@@ -34,6 +35,60 @@ import (
 	"sigs.k8s.io/controller-runtime/pkg/reconcile"
 )
 
+func ExampleBuilder_metadata_only() {
+	logf.SetLogger(zap.New())
+
+	var log = logf.Log.WithName("builder-examples")
+
+	mgr, err := manager.New(config.GetConfigOrDie(), manager.Options{})
+	if err != nil {
+		log.Error(err, "could not create manager")
+		os.Exit(1)
+	}
+
+	cl := mgr.GetClient()
+	err = builder.
+		ControllerManagedBy(mgr).                  // Create the ControllerManagedBy
+		For(&appsv1.ReplicaSet{}).                 // ReplicaSet is the Application API
+		Owns(builder.OnlyMetadata(&corev1.Pod{})). // ReplicaSet owns Pods created by it, and caches them as metadata only
+		Complete(reconcile.Func(func(req reconcile.Request) (reconcile.Result, error) {
+			ctx, cancel := context.WithCancel(context.Background())
+			defer cancel()
+
+			// Read the ReplicaSet
+			rs := &appsv1.ReplicaSet{}
+			err := cl.Get(ctx, req.NamespacedName, rs)
+			if err != nil {
+				return reconcile.Result{}, client.IgnoreNotFound(err)
+			}
+
+			// List the Pods matching the PodTemplate Labels, but only their metadata
+			var podsMeta metav1.PartialObjectMetadataList
+			err = cl.List(ctx, &podsMeta, client.InNamespace(req.Namespace), client.MatchingLabels(rs.Spec.Template.Labels))
+			if err != nil {
+				return reconcile.Result{}, client.IgnoreNotFound(err)
+			}
+
+			// Update the ReplicaSet
+			rs.Labels["pod-count"] = fmt.Sprintf("%v", len(podsMeta.Items))
+			err = cl.Update(ctx, rs)
+			if err != nil {
+				return reconcile.Result{}, err
+			}
+
+			return reconcile.Result{}, nil
+		}))
+	if err != nil {
+		log.Error(err, "could not create controller")
+		os.Exit(1)
+	}
+
+	if err := mgr.Start(signals.SetupSignalHandler()); err != nil {
+		log.Error(err, "could not start manager")
+		os.Exit(1)
+	}
+}
+
 // This example creates a simple application ControllerManagedBy that is configured for ReplicaSets and Pods.
 //
 // * Create a new application for ReplicaSets that manages Pods owned by the ReplicaSet and calls into

pkg/builder/options.go

@@ -0,0 +1,36 @@
+/*
+Copyright 2018 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 builder
+
+import "k8s.io/apimachinery/pkg/runtime"
+
+// OnlyMetadata tells the controller to *only* cache metadata, and to watch
+// the the API server in metadata-only form.  This is useful when watching
+// lots of objects, really big objects, or objects for which you only know
+// the the GVK, but not the structure.  You'll need to pass
+// metav1.PartialObjectMetadata to the client when fetching objects in your
+// reconciler, otherwise you'll end up with a duplicate structured or
+// unstructured cache.
+func OnlyMetadata(obj runtime.Object) runtime.Object {
+	return &onlyMetadataWrapper{obj}
+}
+
+type onlyMetadataWrapper struct {
+	runtime.Object
+}
+
+// }}}