Add feature flag support

cmd/controller/app/controller.go

@@ -117,6 +117,7 @@ func buildControllerContext(opts *options.ControllerOptions) (*controllers.Conte
 		KubeSharedInformerFactory: kubeSharedInformerFactory,
 		SharedInformerFactory:     sharedInformerFactory,
 		Namespace:                 opts.Namespace,
+		Features:                  opts.Features,
 	}, kubeCfg, nil
 }
 

cmd/controller/app/options/options.go

@@ -1,9 +1,12 @@
 package options
 
 import (
+	"strings"
 	"time"
 
 	"github.com/spf13/pflag"
+
+	"github.com/jetstack/navigator/pkg/util/features"
 )
 
 type ControllerOptions struct {
@@ -15,6 +18,9 @@ type ControllerOptions struct {
 	LeaderElectionLeaseDuration time.Duration
 	LeaderElectionRenewDeadline time.Duration
 	LeaderElectionRetryPeriod   time.Duration
+
+	FeatureGatesString string
+	Features           map[string]bool
 }
 
 const (
@@ -26,6 +32,8 @@ const (
 	defaultLeaderElectionLeaseDuration = 15 * time.Second
 	defaultLeaderElectionRenewDeadline = 10 * time.Second
 	defaultLeaderElectionRetryPeriod   = 2 * time.Second
+
+	defaultFeatureGatesString = ""
 )
 
 func NewControllerOptions() *ControllerOptions {
@@ -37,6 +45,8 @@ func NewControllerOptions() *ControllerOptions {
 		LeaderElectionLeaseDuration: defaultLeaderElectionLeaseDuration,
 		LeaderElectionRenewDeadline: defaultLeaderElectionRenewDeadline,
 		LeaderElectionRetryPeriod:   defaultLeaderElectionRetryPeriod,
+		FeatureGatesString:          defaultFeatureGatesString,
+		Features:                    map[string]bool{},
 	}
 }
 
@@ -66,6 +76,8 @@ func (s *ControllerOptions) AddFlags(fs *pflag.FlagSet) {
 	fs.DurationVar(&s.LeaderElectionRetryPeriod, "leader-election-retry-period", defaultLeaderElectionRetryPeriod, ""+
 		"The duration the clients should wait between attempting acquisition and renewal "+
 		"of a leadership. This is only applicable if leader election is enabled.")
+	fs.StringVar(&s.FeatureGatesString, "feature-gates", defaultFeatureGatesString, "A set of key=value pairs that describe feature gates for various features. "+
+		"Options are:\n"+strings.Join(features.KnownFeatures(&features.InitFeatureGates), "\n"))
 }
 
 func (o *ControllerOptions) Validate() error {

cmd/controller/start.go

@@ -12,6 +12,7 @@ import (
 	"github.com/jetstack/navigator/cmd/controller/app/options"
 	_ "github.com/jetstack/navigator/pkg/controllers/cassandra"
 	_ "github.com/jetstack/navigator/pkg/controllers/elasticsearch"
+	"github.com/jetstack/navigator/pkg/util/features"
 )
 
 type NavigatorControllerOptions struct {
@@ -64,6 +65,11 @@ to renew certificates at an appropriate time before expiry.`,
 func (o NavigatorControllerOptions) Validate(args []string) error {
 	errors := []error{}
 	errors = append(errors, o.ControllerOptions.Validate())
+
+	f, err := features.NewFeatureGate(&features.InitFeatureGates, o.ControllerOptions.FeatureGatesString)
+	errors = append(errors, err)
+	o.ControllerOptions.Features = f
+
 	return utilerrors.NewAggregate(errors)
 }
 

contrib/charts/navigator/templates/controller.yaml

@@ -36,6 +36,9 @@ spec:
           - navigator-controller
 {{- if .Values.controller.namespace }}
           - --namespace={{ .Values.controller.namespace }}
+{{- end }}
+{{- if .Values.featureGates }}
+          - --feature-gates={{ .Values.featureGates }}
 {{- end }}
           - --leader-election-namespace={{ .Release.Namespace }}
           - --v={{ .Values.controller.logLevel }}

contrib/charts/navigator/values.yaml

@@ -6,6 +6,9 @@ createAPIService: true
 rbac:
   enabled: true
 
+# A set of key=value pairs that describe feature gates for various features. Use --help to see available flags.
+featureGates: ""
+
 apiserver:
   ## Set to true to skip deploying the apiserver components RBAC policies,
   ## which require cluster admin access to deploy.

pkg/controllers/cassandra/cassandra.go

@@ -32,6 +32,7 @@ import (
 	"github.com/jetstack/navigator/pkg/controllers/cassandra/seedlabeller"
 	"github.com/jetstack/navigator/pkg/controllers/cassandra/service"
 	"github.com/jetstack/navigator/pkg/controllers/cassandra/serviceaccount"
+	"github.com/jetstack/navigator/pkg/util/features"
 )
 
 // NewCassandra returns a new CassandraController that can be used
@@ -55,6 +56,7 @@ type CassandraController struct {
 	roleBindingsListerSynced    cache.InformerSynced
 	queue                       workqueue.RateLimitingInterface
 	recorder                    record.EventRecorder
+	features                    map[string]bool
 }
 
 func NewCassandra(
@@ -69,6 +71,7 @@ func NewCassandra(
 	roles rbacinformers.RoleInformer,
 	roleBindings rbacinformers.RoleBindingInformer,
 	recorder record.EventRecorder,
+	features map[string]bool,
 ) *CassandraController {
 	queue := workqueue.NewNamedRateLimitingQueue(
 		workqueue.DefaultControllerRateLimiter(),
@@ -79,6 +82,7 @@ func NewCassandra(
 		navigatorClient: naviClient,
 		queue:           queue,
 		recorder:        recorder,
+		features:        features,
 	}
 	cassClusters.Informer().AddEventHandler(
 		&controllers.QueuingEventHandler{Queue: queue},
@@ -166,6 +170,10 @@ func NewCassandra(
 func (e *CassandraController) Run(workers int, stopCh <-chan struct{}) error {
 	glog.Infof("Starting Cassandra controller")
 
+	if features.Enabled(e.features, features.Example) {
+		glog.Infof("Example feature flag enabled")
+	}
+
 	if !cache.WaitForCacheSync(
 		stopCh,
 		e.cassListerSynced,
@@ -333,6 +341,7 @@ func CassandraControllerFromContext(ctx *controllers.Context) *CassandraControll
 		ctx.KubeSharedInformerFactory.Rbac().V1beta1().Roles(),
 		ctx.KubeSharedInformerFactory.Rbac().V1beta1().RoleBindings(),
 		ctx.Recorder,
+		ctx.Features,
 	)
 }
 

pkg/controllers/context.go

@@ -18,5 +18,7 @@ type Context struct {
 	KubeSharedInformerFactory kubeinformers.SharedInformerFactory
 	SharedInformerFactory     intinformers.SharedInformerFactory
 
+	Features map[string]bool
+
 	Namespace string
 }

pkg/controllers/elasticsearch/elasticsearch.go

@@ -68,6 +68,8 @@ type ElasticsearchController struct {
 	queue                       workqueue.RateLimitingInterface
 	elasticsearchClusterControl ControlInterface
 	recorder                    record.EventRecorder
+
+	features map[string]bool
 }
 
 // NewElasticsearch returns a new ElasticsearchController that can be used
@@ -89,6 +91,7 @@ func NewElasticsearch(
 	cl kubernetes.Interface,
 	navigatorCl clientset.Interface,
 	recorder record.EventRecorder,
+	features map[string]bool,
 ) *ElasticsearchController {
 	queue := workqueue.NewNamedRateLimitingQueue(workqueue.DefaultControllerRateLimiter(), "elasticsearchCluster")
 	// create a new ElasticsearchController to manage ElasticsearchCluster resources
@@ -97,6 +100,7 @@ func NewElasticsearch(
 		navigatorClient: navigatorCl,
 		queue:           queue,
 		recorder:        recorder,
+		features:        features,
 	}
 
 	// add an event handler to the ElasticsearchCluster informer
@@ -352,6 +356,7 @@ func init() {
 			ctx.Client,
 			ctx.NavigatorClient,
 			ctx.Recorder,
+			ctx.Features,
 		)
 
 		return e.Run