chore: Get resource from cache instead of APIServer

Currently in ACK, at the beginning of the Reconciler for each event, we
get the resource from the k8s APIServer. This is an unecessary call, as
the latest object that triggered the reconciler is already stored in the
informers cache.

With this change, we will be retrieving the resource from the cache
instead of the APIServer.

Author: michaelhtm

Makefile

@@ -35,6 +35,9 @@ mocks: install-mockery ## Build mocks
 	@echo -n "building mocks for sigs.k8s.io/controller-runtime/pkg/client ... "
 	@bin/mockery --quiet --name="(Object|Client|Status|Reader|SubResourceWriter)" --case=underscore --output=mocks/controller-runtime/pkg/client --dir="$(CONTROLLER_RUNTIME_DIR)/pkg/client"
 	@echo "ok."
+	@echo -n "building mocks for sigs.k8s.io/controller-runtime/pkg/cache ... "
+	@bin/mockery --quiet --name="(Cache)" --case=underscore --output=mocks/controller-runtime/pkg/cache --dir="$(CONTROLLER_RUNTIME_DIR)/pkg/cache"
+	@echo "ok."
 
 help:           ## Show this help.
 	@grep -F -h "##" $(MAKEFILE_LIST) | grep -F -v grep | sed -e 's/\\$$//' \

mocks/controller-runtime/pkg/cache/cache.go

@@ -26,6 +26,7 @@ import (
 	"k8s.io/apimachinery/pkg/runtime/schema"
 	"k8s.io/apimachinery/pkg/types"
 	ctrlrt "sigs.k8s.io/controller-runtime"
+	"sigs.k8s.io/controller-runtime/pkg/cache"
 	"sigs.k8s.io/controller-runtime/pkg/client"
 	k8sctrlutil "sigs.k8s.io/controller-runtime/pkg/controller/controllerutil"
 	"sigs.k8s.io/controller-runtime/pkg/predicate"
@@ -57,7 +58,7 @@ type adoptionReconciler struct {
 // of an upstream controller-runtime.Manager
 func (r *adoptionReconciler) BindControllerManager(mgr ctrlrt.Manager) error {
 	r.kc = mgr.GetClient()
-	r.apiReader = mgr.GetAPIReader()
+	r.ackResourceCache = mgr.GetCache()
 	return ctrlrt.NewControllerManagedBy(
 		mgr,
 	).For(
@@ -251,7 +252,7 @@ func (r *adoptionReconciler) Sync(
 
 	// Only create the described resource if it does not already exist
 	// in k8s cluster.
-	if err := r.apiReader.Get(ctx, types.NamespacedName{
+	if err := r.ackResourceCache.Get(ctx, types.NamespacedName{
 		Namespace: described.MetaObject().GetNamespace(),
 		Name:      described.MetaObject().GetName(),
 	}, described.RuntimeObject()); err != nil {
@@ -306,15 +307,15 @@ func (r *adoptionReconciler) getAdoptedResource(
 	req ctrlrt.Request,
 ) (*ackv1alpha1.AdoptedResource, error) {
 	ro := &ackv1alpha1.AdoptedResource{}
-	// Here we use k8s APIReader to read the k8s object by making the
+	// Here we use k8s ACKResourceCache to read the k8s object by making the
 	// direct call to k8s apiserver instead of using k8sClient.
 	// The reason is that k8sClient uses a cache and sometimes k8sClient can
 	// return stale copy of object.
 	// It is okay to make direct call to k8s apiserver because we are only
 	// making single read call for complete reconciler loop.
 	// See following issue for more details:
 	// https://github.com/aws-controllers-k8s/community/issues/894
-	if err := r.apiReader.Get(ctx, req.NamespacedName, ro); err != nil {
+	if err := r.ackResourceCache.Get(ctx, req.NamespacedName, ro); err != nil {
 		return nil, err
 	}
 	return ro, nil
@@ -615,7 +616,7 @@ func NewAdoptionReconcilerWithClient(
 	metrics *ackmetrics.Metrics,
 	cache ackrtcache.Caches,
 	kc client.Client,
-	apiReader client.Reader,
+	ackResourceCache cache.Cache,
 ) acktypes.AdoptedResourceReconciler {
 	return &adoptionReconciler{
 		reconciler: reconciler{
@@ -625,7 +626,7 @@ func NewAdoptionReconcilerWithClient(
 			metrics:   metrics,
 			cache:     cache,
 			kc:        kc,
-			apiReader: apiReader,
+			ackResourceCache: ackResourceCache,
 		},
 	}
 }