From b4097f91bc3fb52eaf4333edf06658932cb73ec0 Mon Sep 17 00:00:00 2001
From: yue9944882 <291271447@qq.com>
Date: Wed, 24 Feb 2021 14:38:51 +0800
Subject: [PATCH] introducing ClusterClaim feature gate to opt-out from
 list-watching cluster-claims

Signed-off-by: yue9944882 <291271447@qq.com>
---
 pkg/features/feature.go | 44 +++++++++++++++++++++++++++++++++++++++++
 pkg/spoke/spokeagent.go | 29 ++++++++++++++++-----------
 2 files changed, 62 insertions(+), 11 deletions(-)
 create mode 100644 pkg/features/feature.go

diff --git a/pkg/features/feature.go b/pkg/features/feature.go
new file mode 100644
index 000000000..16ba90220
--- /dev/null
+++ b/pkg/features/feature.go
@@ -0,0 +1,44 @@
+package features
+
+import (
+	"k8s.io/component-base/featuregate"
+	"k8s.io/klog/v2"
+)
+
+const (
+	// Every feature gate should add method here following this template:
+	//
+	// // owner: @username
+	// // alpha: v1.X
+	// MyFeature featuregate.Feature = "MyFeature"
+
+	// ClusterClaim will start a new controller in the spoke-agent to manage the cluster-claim
+	// resources in the managed cluster.
+	//
+	// The cluster-claim controller is majorly for collecting claims and updating claims field
+	// in managedcluster status. When it exceeds the limit specified by "--max-custom-cluster-claims",
+	// the extra claims will be truncated.
+	//
+	// If it is disabled, the user will see empty claims field in managedcluster status. The
+	// deployer who disable the feature may need to update claim field in managed cluster status
+	// itself to avoid impact to users.
+	ClusterClaim featuregate.Feature = "ClusterClaim"
+)
+
+var (
+	// DefaultMutableFeatureGate is made up of multiple mutable feature-gates.
+	DefaultMutableFeatureGate featuregate.MutableFeatureGate = featuregate.NewFeatureGate()
+)
+
+func init() {
+	if err := DefaultMutableFeatureGate.Add(defaultRegistrationFeatureGates); err != nil {
+		klog.Fatalf("Unexpected error: %v", err)
+	}
+}
+
+// defaultRegistrationFeatureGates consists of all known ocm-registration
+// feature keys.  To add a new feature, define a key for it above and
+// add it here.
+var defaultRegistrationFeatureGates = map[featuregate.Feature]featuregate.FeatureSpec{
+	ClusterClaim: {Default: true, PreRelease: featuregate.Beta},
+}
diff --git a/pkg/spoke/spokeagent.go b/pkg/spoke/spokeagent.go
index 12fde3177..7215d2751 100644
--- a/pkg/spoke/spokeagent.go
+++ b/pkg/spoke/spokeagent.go
@@ -4,6 +4,7 @@ import (
 	"context"
 	"errors"
 	"fmt"
+	"github.com/openshift/library-go/pkg/controller/factory"
 	"io/ioutil"
 	"os"
 	"path"
@@ -11,6 +12,7 @@ import (
 
 	clusterv1client "github.com/open-cluster-management/api/client/cluster/clientset/versioned"
 	clusterv1informers "github.com/open-cluster-management/api/client/cluster/informers/externalversions"
+	"github.com/open-cluster-management/registration/pkg/features"
 	"github.com/open-cluster-management/registration/pkg/helpers"
 	"github.com/open-cluster-management/registration/pkg/spoke/hubclientcert"
 	"github.com/open-cluster-management/registration/pkg/spoke/managedcluster"
@@ -255,22 +257,24 @@ func (o *SpokeAgentOptions) RunSpokeAgent(ctx context.Context, controllerContext
 		o.ClusterHealthCheckPeriod,
 		controllerContext.EventRecorder,
 	)
-
 	spokeClusterClient, err := clusterv1client.NewForConfig(controllerContext.KubeConfig)
 	if err != nil {
 		return err
 	}
 	spokeClusterInformers := clusterv1informers.NewSharedInformerFactory(spokeClusterClient, 10*time.Minute)
 
-	// create managedClusterClaimController to sync cluster claims
-	managedClusterClaimController := managedcluster.NewManagedClusterClaimController(
-		o.ClusterName,
-		o.MaxCustomClusterClaims,
-		hubClusterClient,
-		hubClusterInformerFactory.Cluster().V1().ManagedClusters(),
-		spokeClusterInformers.Cluster().V1alpha1().ClusterClaims(),
-		controllerContext.EventRecorder,
-	)
+	var managedClusterClaimController factory.Controller
+	if features.DefaultMutableFeatureGate.Enabled(features.ClusterClaim) {
+		// create managedClusterClaimController to sync cluster claims
+		managedClusterClaimController = managedcluster.NewManagedClusterClaimController(
+			o.ClusterName,
+			o.MaxCustomClusterClaims,
+			hubClusterClient,
+			hubClusterInformerFactory.Cluster().V1().ManagedClusters(),
+			spokeClusterInformers.Cluster().V1alpha1().ClusterClaims(),
+			controllerContext.EventRecorder,
+		)
+	}
 
 	go hubKubeInformerFactory.Start(ctx.Done())
 	go hubClusterInformerFactory.Start(ctx.Done())
@@ -282,7 +286,9 @@ func (o *SpokeAgentOptions) RunSpokeAgent(ctx context.Context, controllerContext
 	go managedClusterJoiningController.Run(ctx, 1)
 	go managedClusterLeaseController.Run(ctx, 1)
 	go managedClusterHealthCheckController.Run(ctx, 1)
-	go managedClusterClaimController.Run(ctx, 1)
+	if features.DefaultMutableFeatureGate.Enabled(features.ClusterClaim) {
+		go managedClusterClaimController.Run(ctx, 1)
+	}
 
 	<-ctx.Done()
 	return nil
@@ -290,6 +296,7 @@ func (o *SpokeAgentOptions) RunSpokeAgent(ctx context.Context, controllerContext
 
 // AddFlags registers flags for Agent
 func (o *SpokeAgentOptions) AddFlags(fs *pflag.FlagSet) {
+	features.DefaultMutableFeatureGate.AddFlag(fs)
 	fs.StringVar(&o.ClusterName, "cluster-name", o.ClusterName,
 		"If non-empty, will use as cluster name instead of generated random name.")
 	fs.StringVar(&o.BootstrapKubeconfig, "bootstrap-kubeconfig", o.BootstrapKubeconfig,