Make Pod informer registration optional

Changes:
1. Added support for feature gate flag parsing
   (Sample flag looks like "--feature-gates=VolumeInUseErrorHandler=true")
2. Register Pod informer only if feature is enabled.

Author: saikat-royc

cmd/csi-resizer/main.go

@@ -18,19 +18,25 @@ package main
 
 import (
 	"context"
-	"flag"
+	goflag "flag"
 	"fmt"
-	"k8s.io/client-go/util/workqueue"
 	"os"
 	"time"
 
+	flag "github.com/spf13/pflag"
+	"k8s.io/client-go/util/workqueue"
+
 	"github.com/kubernetes-csi/csi-lib-utils/leaderelection"
 	"github.com/kubernetes-csi/external-resizer/pkg/controller"
 	"github.com/kubernetes-csi/external-resizer/pkg/resizer"
 	"github.com/kubernetes-csi/external-resizer/pkg/util"
 
+	"strings"
+
 	"k8s.io/apimachinery/pkg/util/wait"
+	utilfeature "k8s.io/apiserver/pkg/util/feature"
 	"k8s.io/client-go/informers"
+	utilflag "k8s.io/component-base/cli/flag"
 	"k8s.io/klog"
 )
 
@@ -53,14 +59,22 @@ var (
 	metricsAddress = flag.String("metrics-address", "", "The TCP network address where the prometheus metrics endpoint will listen (example: `:8080`). The default is empty string, which means metrics endpoint is disabled.")
 	metricsPath    = flag.String("metrics-path", "/metrics", "The HTTP path where prometheus metrics will be exposed. Default is `/metrics`.")
 
-	version = "unknown"
+	version      = "unknown"
+	featureGates map[string]bool
 )
 
 func main() {
 	klog.InitFlags(nil)
 	flag.Set("logtostderr", "true")
+	flag.Var(utilflag.NewMapStringBool(&featureGates), "feature-gates", "A set of key=value pairs that describe feature gates. "+
+		"Options are:\n"+strings.Join(utilfeature.DefaultFeatureGate.KnownFeatures(), "\n"))
+	flag.CommandLine.AddGoFlagSet(goflag.CommandLine)
 	flag.Parse()
 
+	if err := utilfeature.DefaultMutableFeatureGate.SetFromMap(featureGates); err != nil {
+		klog.Fatal(err.Error())
+	}
+
 	if *showVersion {
 		fmt.Println(os.Args[0], version)
 		os.Exit(0)

go.mod

@@ -6,10 +6,13 @@ require (
 	github.com/container-storage-interface/spec v1.2.0
 	github.com/imdario/mergo v0.3.9 // indirect
 	github.com/kubernetes-csi/csi-lib-utils v0.7.0
+	github.com/spf13/pflag v1.0.5
 	google.golang.org/grpc v1.28.0
 	k8s.io/api v0.18.0
 	k8s.io/apimachinery v0.18.0
+	k8s.io/apiserver v0.18.4
 	k8s.io/client-go v0.18.0
+	k8s.io/component-base v0.18.0
 	k8s.io/csi-translation-lib v0.18.0
 	k8s.io/klog v1.0.0
 )

pkg/controller/controller.go

@@ -21,6 +21,7 @@ import (
 	"fmt"
 	"time"
 
+	"github.com/kubernetes-csi/external-resizer/pkg/features"
 	"github.com/kubernetes-csi/external-resizer/pkg/resizer"
 	"github.com/kubernetes-csi/external-resizer/pkg/util"
 	"google.golang.org/grpc/codes"
@@ -31,6 +32,7 @@ import (
 	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
 	utilruntime "k8s.io/apimachinery/pkg/util/runtime"
 	"k8s.io/apimachinery/pkg/util/wait"
+	utilfeature "k8s.io/apiserver/pkg/util/feature"
 	"k8s.io/client-go/informers"
 	"k8s.io/client-go/kubernetes"
 	"k8s.io/client-go/kubernetes/scheme"
@@ -76,10 +78,6 @@ func NewResizeController(
 	pvcRateLimiter workqueue.RateLimiter) ResizeController {
 	pvInformer := informerFactory.Core().V1().PersistentVolumes()
 	pvcInformer := informerFactory.Core().V1().PersistentVolumeClaims()
-
-	// list pods so as we can identify PVC that are in-use
-	podInformer := informerFactory.Core().V1().Pods()
-
 	eventBroadcaster := record.NewBroadcaster()
 	eventBroadcaster.StartLogging(klog.Infof)
 	eventBroadcaster.StartRecordingToSink(&corev1.EventSinkImpl{Interface: kubeClient.CoreV1().Events(v1.NamespaceAll)})
@@ -90,18 +88,16 @@ func NewResizeController(
 		pvcRateLimiter, fmt.Sprintf("%s-pvc", name))
 
 	ctrl := &resizeController{
-		name:            name,
-		resizer:         resizer,
-		kubeClient:      kubeClient,
-		pvLister:        pvInformer.Lister(),
-		pvSynced:        pvInformer.Informer().HasSynced,
-		pvcLister:       pvcInformer.Lister(),
-		pvcSynced:       pvcInformer.Informer().HasSynced,
-		podLister:       podInformer.Lister(),
-		podListerSynced: podInformer.Informer().HasSynced,
-		claimQueue:      claimQueue,
-		eventRecorder:   eventRecorder,
-		usedPVCs:        newUsedPVCStore(),
+		name:          name,
+		resizer:       resizer,
+		kubeClient:    kubeClient,
+		pvLister:      pvInformer.Lister(),
+		pvSynced:      pvInformer.Informer().HasSynced,
+		pvcLister:     pvcInformer.Lister(),
+		pvcSynced:     pvcInformer.Informer().HasSynced,
+		claimQueue:    claimQueue,
+		eventRecorder: eventRecorder,
+		usedPVCs:      newUsedPVCStore(),
 	}
 
 	// Add a resync period as the PVC's request size can be resized again when we handling
@@ -112,11 +108,18 @@ func NewResizeController(
 		DeleteFunc: ctrl.deletePVC,
 	}, resyncPeriod)
 
-	podInformer.Informer().AddEventHandlerWithResyncPeriod(cache.ResourceEventHandlerFuncs{
-		AddFunc:    ctrl.addPod,
-		DeleteFunc: ctrl.deletePod,
-		UpdateFunc: ctrl.updatePod,
-	}, resyncPeriod)
+	if isVolumeInUserErrorHandlerEnabled() {
+		// list pods so as we can identify PVC that are in-use
+		klog.Infof("Register Pod informer for resizer %s", ctrl.name)
+		podInformer := informerFactory.Core().V1().Pods()
+		ctrl.podLister = podInformer.Lister()
+		ctrl.podListerSynced = podInformer.Informer().HasSynced
+		podInformer.Informer().AddEventHandlerWithResyncPeriod(cache.ResourceEventHandlerFuncs{
+			AddFunc:    ctrl.addPod,
+			DeleteFunc: ctrl.deletePod,
+			UpdateFunc: ctrl.updatePod,
+		}, resyncPeriod)
+	}
 
 	return ctrl
 }
@@ -235,8 +238,12 @@ func (ctrl *resizeController) Run(
 	defer klog.Infof("Shutting down external resizer %s", ctrl.name)
 
 	stopCh := ctx.Done()
+	informersSyncd := []cache.InformerSynced{ctrl.pvSynced, ctrl.pvcSynced}
+	if isVolumeInUserErrorHandlerEnabled() {
+		informersSyncd = append(informersSyncd, ctrl.podListerSynced)
+	}
 
-	if !cache.WaitForCacheSync(stopCh, ctrl.pvSynced, ctrl.pvcSynced, ctrl.podListerSynced) {
+	if !cache.WaitForCacheSync(stopCh, informersSyncd...) {
 		klog.Errorf("Cannot sync pod, pv or pvc caches")
 		return
 	}
@@ -523,3 +530,7 @@ func inUseError(err error) bool {
 	}
 	return false
 }
+
+func isVolumeInUserErrorHandlerEnabled() bool {
+	return utilfeature.DefaultFeatureGate.Enabled(features.VolumeInUseErrorHandler)
+}

pkg/controller/controller_test.go

@@ -5,6 +5,7 @@ import (
 	"testing"
 	"time"
 
+	utilfeature "k8s.io/apiserver/pkg/util/feature"
 	"k8s.io/client-go/util/workqueue"
 
 	"github.com/kubernetes-csi/csi-lib-utils/metrics"
@@ -21,9 +22,17 @@ import (
 	"k8s.io/client-go/kubernetes/fake"
 )
 
+func setupVolumeInUseErrorHandler(enable bool) {
+	featureGates := map[string]bool{
+		"VolumeInUseErrorHandler": enable,
+	}
+	utilfeature.DefaultMutableFeatureGate.SetFromMap(featureGates)
+}
+
 func TestController(t *testing.T) {
 	blockVolumeMode := v1.PersistentVolumeBlock
 	fsVolumeMode := v1.PersistentVolumeFilesystem
+
 	for _, test := range []struct {
 		Name string
 		PVC  *v1.PersistentVolumeClaim
@@ -37,7 +46,8 @@ func TestController(t *testing.T) {
 		// is PVC being expanded in-use
 		pvcInUse bool
 		// does PVC being expanded has Failed Precondition errors
-		pvcHasInUseErrors bool
+		pvcHasInUseErrors              bool
+		disableVolumeInUseErrorHandler bool
 	}{
 		{
 			Name:          "Invalid key",
@@ -130,7 +140,66 @@ func TestController(t *testing.T) {
 			pvcHasInUseErrors: true,
 			pvcInUse:          false,
 		},
+		// test cases with feat disabled.
+		{
+			Name:                           "Feat disabled, Resize PVC, no FS resize, pvc-inuse with failedprecondition",
+			PVC:                            createPVC(2, 1),
+			PV:                             createPV(1, "testPVC", defaultNS, "foobar", &fsVolumeMode),
+			CreateObjects:                  true,
+			CallCSIExpand:                  true,
+			pvcHasInUseErrors:              true,
+			pvcInUse:                       true,
+			disableVolumeInUseErrorHandler: true,
+		},
+		{
+			Name:                           "Feat disabled, Resize PVC, no FS resize, pvc-inuse but no failedprecondition error",
+			PVC:                            createPVC(2, 1),
+			PV:                             createPV(1, "testPVC", defaultNS, "foobar", &fsVolumeMode),
+			CreateObjects:                  true,
+			CallCSIExpand:                  true,
+			pvcHasInUseErrors:              false,
+			pvcInUse:                       true,
+			disableVolumeInUseErrorHandler: true,
+		},
+		{
+			Name:                           "Feat disabled, Resize PVC, no FS resize, pvc not in-use but has failedprecondition error",
+			PVC:                            createPVC(2, 1),
+			PV:                             createPV(1, "testPVC", defaultNS, "foobar", &fsVolumeMode),
+			CreateObjects:                  true,
+			CallCSIExpand:                  true,
+			pvcHasInUseErrors:              true,
+			pvcInUse:                       false,
+			disableVolumeInUseErrorHandler: true,
+		},
+		{
+			Name:                           "Feat disabled, Block Resize PVC with FS resize",
+			PVC:                            createPVC(2, 1),
+			PV:                             createPV(1, "testPVC", defaultNS, "foobar", &blockVolumeMode),
+			CreateObjects:                  true,
+			NodeResize:                     true,
+			CallCSIExpand:                  true,
+			expectBlockVolume:              true,
+			disableVolumeInUseErrorHandler: true,
+		},
+		{
+			Name:                           "Feat disabled, Resize PVC with FS resize",
+			PVC:                            createPVC(2, 1),
+			PV:                             createPV(1, "testPVC", defaultNS, "foobar", &fsVolumeMode),
+			CreateObjects:                  true,
+			NodeResize:                     true,
+			CallCSIExpand:                  true,
+			disableVolumeInUseErrorHandler: true,
+		},
+		{
+			Name:                           "Feat disabled, Resize PVC, no FS resize",
+			PVC:                            createPVC(2, 1),
+			PV:                             createPV(1, "testPVC", defaultNS, "foobar", &fsVolumeMode),
+			CreateObjects:                  true,
+			CallCSIExpand:                  true,
+			disableVolumeInUseErrorHandler: true,
+		},
 	} {
+		setupVolumeInUseErrorHandler(!test.disableVolumeInUseErrorHandler)
 		client := csi.NewMockClient("mock", test.NodeResize, true, true)
 		driverName, _ := client.GetDriverName(context.TODO())
 

pkg/features/features.go

@@ -0,0 +1,36 @@
+/*
+Copyright 2020 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 features
+
+import (
+	"k8s.io/apiserver/pkg/util/feature"
+	"k8s.io/component-base/featuregate"
+)
+
+const (
+	VolumeInUseErrorHandler featuregate.Feature = "VolumeInUseErrorHandler"
+)
+
+func init() {
+	feature.DefaultMutableFeatureGate.Add(defaultKubernetesFeatureGates)
+}
+
+// defaultKubernetesFeatureGates consists of all known feature keys specific to external-resizer.
+// To add a new feature, define a key for it above and add it here.
+var defaultKubernetesFeatureGates = map[featuregate.Feature]featuregate.FeatureSpec{
+	VolumeInUseErrorHandler: {Default: false, PreRelease: featuregate.GA},
+}