🐛 filter global namespace while looking for cluster scoped resources (kubernetes-sigs#1520)

* 🐛 filter global namespace while looking for cluster scoped resources

In the current implementation of multinamespaced cache, we look at
global namespace while listing objects from all namespaced. Global namespace
should not be looked at while fetching namespaced resources.

* create a cluser scoped cache separately

Signed-off-by: varshaprasad96 <[email protected]>

Author: varshaprasad96

pkg/cache/multi_namespace_cache.go

@@ -41,7 +41,7 @@ const globalCache = "_cluster-scope"
 // MultiNamespacedCacheBuilder - Builder function to create a new multi-namespaced cache.
 // This will scope the cache to a list of namespaces. Listing for all namespaces
 // will list for all the namespaces that this knows about. By default this will create
-// a global cache for cluster scoped resource (having empty namespace). Note that this is not intended
+// a global cache for cluster scoped resource. Note that this is not intended
 // to be used for excluding namespaces, this is better done via a Predicate. Also note that
 // you may face performance issues when using this with a high number of namespaces.
 func MultiNamespacedCacheBuilder(namespaces []string) NewCacheFunc {
@@ -50,9 +50,15 @@ func MultiNamespacedCacheBuilder(namespaces []string) NewCacheFunc {
 		if err != nil {
 			return nil, err
 		}
-		// create a cache for cluster scoped resources
-		namespaces = append(namespaces, globalCache)
+
 		caches := map[string]Cache{}
+
+		// create a cache for cluster scoped resources
+		gCache, err := New(config, opts)
+		if err != nil {
+			return nil, fmt.Errorf("error creating global cache %v", err)
+		}
+
 		for _, ns := range namespaces {
 			opts.Namespace = ns
 			c, err := New(config, opts)
@@ -61,7 +67,7 @@ func MultiNamespacedCacheBuilder(namespaces []string) NewCacheFunc {
 			}
 			caches[ns] = c
 		}
-		return &multiNamespaceCache{namespaceToCache: caches, Scheme: opts.Scheme, RESTMapper: opts.Mapper}, nil
+		return &multiNamespaceCache{namespaceToCache: caches, Scheme: opts.Scheme, RESTMapper: opts.Mapper, clusterCache: gCache}, nil
 	}
 }
 
@@ -73,36 +79,82 @@ type multiNamespaceCache struct {
 	namespaceToCache map[string]Cache
 	Scheme           *runtime.Scheme
 	RESTMapper       meta.RESTMapper
+	clusterCache     Cache
 }
 
 var _ Cache = &multiNamespaceCache{}
 
 // Methods for multiNamespaceCache to conform to the Informers interface
 func (c *multiNamespaceCache) GetInformer(ctx context.Context, obj client.Object) (Informer, error) {
 	informers := map[string]Informer{}
+
+	// If the object is clusterscoped, get the informer from clusterCache,
+	// if not use the namespaced caches.
+	isNamespaced, err := objectutil.IsAPINamespaced(obj, c.Scheme, c.RESTMapper)
+	if err != nil {
+		return nil, err
+	}
+	if !isNamespaced {
+		clusterCacheInf, err := c.clusterCache.GetInformer(ctx, obj)
+		if err != nil {
+			return nil, err
+		}
+		informers[globalCache] = clusterCacheInf
+
+		return &multiNamespaceInformer{namespaceToInformer: informers}, nil
+	}
+
 	for ns, cache := range c.namespaceToCache {
 		informer, err := cache.GetInformer(ctx, obj)
 		if err != nil {
 			return nil, err
 		}
 		informers[ns] = informer
 	}
+
 	return &multiNamespaceInformer{namespaceToInformer: informers}, nil
 }
 
 func (c *multiNamespaceCache) GetInformerForKind(ctx context.Context, gvk schema.GroupVersionKind) (Informer, error) {
 	informers := map[string]Informer{}
+
+	// If the object is clusterscoped, get the informer from clusterCache,
+	// if not use the namespaced caches.
+	isNamespaced, err := objectutil.IsAPINamespacedWithGVK(gvk, c.Scheme, c.RESTMapper)
+	if err != nil {
+		return nil, err
+	}
+	if !isNamespaced {
+		clusterCacheInf, err := c.clusterCache.GetInformerForKind(ctx, gvk)
+		if err != nil {
+			return nil, err
+		}
+		informers[globalCache] = clusterCacheInf
+
+		return &multiNamespaceInformer{namespaceToInformer: informers}, nil
+	}
+
 	for ns, cache := range c.namespaceToCache {
 		informer, err := cache.GetInformerForKind(ctx, gvk)
 		if err != nil {
 			return nil, err
 		}
 		informers[ns] = informer
 	}
+
 	return &multiNamespaceInformer{namespaceToInformer: informers}, nil
 }
 
 func (c *multiNamespaceCache) Start(ctx context.Context) error {
+	// start global cache
+	go func() {
+		err := c.clusterCache.Start(ctx)
+		if err != nil {
+			log.Error(err, "cluster scoped cache failed to start")
+		}
+	}()
+
+	// start namespaced caches
 	for ns, cache := range c.namespaceToCache {
 		go func(ns string, cache Cache) {
 			err := cache.Start(ctx)
@@ -111,6 +163,7 @@ func (c *multiNamespaceCache) Start(ctx context.Context) error {
 			}
 		}(ns, cache)
 	}
+
 	<-ctx.Done()
 	return nil
 }
@@ -122,10 +175,24 @@ func (c *multiNamespaceCache) WaitForCacheSync(ctx context.Context) bool {
 			synced = s
 		}
 	}
+
+	// check if cluster scoped cache has synced
+	if !c.clusterCache.WaitForCacheSync(ctx) {
+		synced = false
+	}
 	return synced
 }
 
 func (c *multiNamespaceCache) IndexField(ctx context.Context, obj client.Object, field string, extractValue client.IndexerFunc) error {
+	isNamespaced, err := objectutil.IsAPINamespaced(obj, c.Scheme, c.RESTMapper)
+	if err != nil {
+		return nil
+	}
+
+	if !isNamespaced {
+		return c.clusterCache.IndexField(ctx, obj, field, extractValue)
+	}
+
 	for _, cache := range c.namespaceToCache {
 		if err := cache.IndexField(ctx, obj, field, extractValue); err != nil {
 			return err
@@ -142,8 +209,7 @@ func (c *multiNamespaceCache) Get(ctx context.Context, key client.ObjectKey, obj
 
 	if !isNamespaced {
 		// Look into the global cache to fetch the object
-		cache := c.namespaceToCache[globalCache]
-		return cache.Get(ctx, key, obj)
+		return c.clusterCache.Get(ctx, key, obj)
 	}
 
 	cache, ok := c.namespaceToCache[key.Namespace]
@@ -165,8 +231,7 @@ func (c *multiNamespaceCache) List(ctx context.Context, list client.ObjectList,
 
 	if !isNamespaced {
 		// Look at the global cache to get the objects with the specified GVK
-		cache := c.namespaceToCache[globalCache]
-		return cache.List(ctx, list, opts...)
+		return c.clusterCache.List(ctx, list, opts...)
 	}
 
 	if listOpts.Namespace != corev1.NamespaceAll {

pkg/internal/objectutil/objectutil.go

@@ -55,7 +55,13 @@ func IsAPINamespaced(obj runtime.Object, scheme *runtime.Scheme, restmapper apim
 		return false, err
 	}
 
-	restmapping, err := restmapper.RESTMapping(schema.GroupKind{Group: gvk.Group, Kind: gvk.Kind})
+	return IsAPINamespacedWithGVK(gvk, scheme, restmapper)
+}
+
+// IsAPINamespacedWithGVK returns true if the object having the provided
+// GVK is namespace scoped.
+func IsAPINamespacedWithGVK(gk schema.GroupVersionKind, scheme *runtime.Scheme, restmapper apimeta.RESTMapper) (bool, error) {
+	restmapping, err := restmapper.RESTMapping(schema.GroupKind{Group: gk.Group, Kind: gk.Kind})
 	if err != nil {
 		return false, fmt.Errorf("failed to get restmapping: %w", err)
 	}