ConfigMap informer should only watch --asm-configmap-based-config-nam…

…espace

This avoids making total ConfigMap size part of the scalability
profile of the controller.

Testing: Manual

- hack/run-local-glbc.sh --enable-asm-config-map-config \
-v=3 --asm-configmap-based-config-namespace=default
- Created ConfigMaps in `default` namespace.
- Observed only updates to the default namespace ConfigMaps were being
observed in the controller.

Notes

One interesting thing to note is that watching kube-system has a
non-trivial amount of constant activity due to leader election leases.
This can cause CPU usage if there are a large number of components
running leader election using the same namespace.

pkg/cmconfig/controller.go

@@ -90,11 +90,13 @@ func (c *ConfigMapConfigController) DisableASM() {
 
 // SetASMReadyTrue update the ASMReady to True.
 func (c *ConfigMapConfigController) SetASMReadyTrue() {
+	klog.V(0).Info("SetASMReadyTrue")
 	c.updateASMReady(trueValue)
 }
 
 // SetASMReadyFalse update the ASMReady to False.
 func (c *ConfigMapConfigController) SetASMReadyFalse() {
+	klog.V(0).Info("SetASMReadyFalse")
 	c.updateASMReady(falseValue)
 }
 
@@ -125,10 +127,15 @@ func (c *ConfigMapConfigController) RegisterInformer(configMapInformer cache.Sha
 }
 
 func (c *ConfigMapConfigController) processItem(obj interface{}, cancel func()) {
+	klog.V(4).Infof("ConfigMapConfigController.processItem()")
+
 	configMap, ok := obj.(*v1.ConfigMap)
 	if !ok {
 		klog.Errorf("ConfigMapConfigController: failed to convert informer object to ConfigMap.")
 	}
+
+	klog.V(3).Infof("ConfigMapConfigController.processItem '%s.%s'", configMap.Namespace, configMap.Name)
+
 	if configMap.Namespace != c.configMapNamespace || configMap.Name != c.configMapName {
 		return
 	}

pkg/context/context.go

@@ -28,6 +28,7 @@ import (
 	"k8s.io/apimachinery/pkg/types"
 	"k8s.io/client-go/dynamic"
 	"k8s.io/client-go/dynamic/dynamicinformer"
+	informers "k8s.io/client-go/informers"
 	informerv1 "k8s.io/client-go/informers/core/v1"
 	discoveryinformer "k8s.io/client-go/informers/discovery/v1"
 	informernetworking "k8s.io/client-go/informers/networking/v1"
@@ -224,8 +225,10 @@ func (ctx *ControllerContext) Init() {
 	klog.V(2).Infof("Controller Context initializing with %+v", ctx.ControllerContextConfig)
 	// Initialize controller context internals based on ASMConfigMap
 	if ctx.EnableASMConfigMap {
-		configMapInformer := informerv1.NewConfigMapInformer(ctx.KubeClient, ctx.Namespace, ctx.ResyncPeriod, utils.NewNamespaceIndexer())
-		ctx.ConfigMapInformer = configMapInformer
+		klog.Infof("ASMConfigMap is enabled")
+
+		informerFactory := informers.NewSharedInformerFactoryWithOptions(ctx.KubeClient, ctx.ResyncPeriod, informers.WithNamespace(ctx.ASMConfigMapNamespace))
+		ctx.ConfigMapInformer = informerFactory.Core().V1().ConfigMaps().Informer()
 		ctx.ASMConfigController = cmconfig.NewConfigMapConfigController(ctx.KubeClient, ctx.Recorder(ctx.ASMConfigMapNamespace), ctx.ASMConfigMapNamespace, ctx.ASMConfigMapName)
 
 		cmConfig := ctx.ASMConfigController.GetConfig()
@@ -235,7 +238,6 @@ func (ctx *ControllerContext) Init() {
 			ctx.ASMConfigController.SetASMReadyFalse()
 		}
 	}
-
 }
 
 func (ctx *ControllerContext) initEnableASM() {
@@ -247,6 +249,8 @@ func (ctx *ControllerContext) initEnableASM() {
 		destinationRuleCRDName = "destinationrules.networking.istio.io"
 	)
 
+	klog.V(0).Infof("ASM mode is enabled from ConfigMap")
+
 	apiextensionClient, err := apiextensionsclientset.NewForConfig(ctx.KubeConfig)
 	if err != nil {
 		msg := fmt.Sprintf("Failed to create ApiextensionClient for DestinationRule, disabling ASM Mode, error: %s", err)