✨ pkg/manager/*: Add MetricsServingDisabled option

MetricsServingDisabled option when set to true disables serving metrics
by manager.

Author: lilic

pkg/manager/internal.go

@@ -42,10 +42,10 @@ import (
 var log = logf.RuntimeLog.WithName("manager")
 
 type controllerManager struct {
-	// config is the rest.config used to talk to the apiserver.  Required.
+	// config is the rest.config used to talk to the apiserver. Required.
 	config *rest.Config
 
-	// scheme is the scheme injected into Controllers, EventHandlers, Sources and Predicates.  Defaults
+	// scheme is the scheme injected into Controllers, EventHandlers, Sources and Predicates. Defaults
 	// to scheme.scheme.
 	scheme *runtime.Scheme
 
@@ -75,6 +75,10 @@ type controllerManager struct {
 	// metricsListener is used to serve prometheus metrics
 	metricsListener net.Listener
 
+	// metricsServingDisabled is used to disable the serving of metrics
+	// by default these are enabled, as the value is false.
+	metricsServingDisabled bool
+
 	mu      sync.Mutex
 	started bool
 	errChan chan error
@@ -167,7 +171,7 @@ func (cm *controllerManager) GetRESTMapper() meta.RESTMapper {
 	return cm.mapper
 }
 
-func (cm *controllerManager) serveMetrics(stop <-chan struct{}) {
+func (cm *controllerManager) ServeMetrics(stop <-chan struct{}) {
 	handler := promhttp.HandlerFor(metrics.Registry, promhttp.HandlerOpts{
 		ErrorHandling: promhttp.HTTPErrorOnError,
 	})
@@ -200,8 +204,8 @@ func (cm *controllerManager) Start(stop <-chan struct{}) error {
 	// Metrics should be served whether the controller is leader or not.
 	// (If we don't serve metrics for non-leaders, prometheus will still scrape
 	// the pod but will get a connection refused)
-	if cm.metricsListener != nil {
-		go cm.serveMetrics(cm.internalStop)
+	if cm.metricsListener != nil && !cm.metricsServingDisabled {
+		go cm.ServeMetrics(cm.internalStop)
 	}
 
 	if cm.resourceLock != nil {

pkg/manager/manager.go

@@ -46,6 +46,10 @@ type Manager interface {
 	// implements the inject interface - e.g. inject.Client
 	Add(Runnable) error
 
+	// ServeMetrics serves the metrics until the stop channel is closed.
+	// It serves the metrics on `/metrics` on the port configured through the MetricsBindAddress.
+	ServeMetrics(<-chan struct{})
+
 	// SetFields will set any dependencies on an object for which the object has implemented the inject
 	// interface - e.g. inject.Client.
 	SetFields(interface{}) error
@@ -116,6 +120,11 @@ type Options struct {
 	// for serving prometheus metrics
 	MetricsBindAddress string
 
+	// MetricsServingDisabled does not serve the metrics. This can be used when
+	// user wants to serve the metrics separately.
+	// If not set it is set to false by default.
+	MetricsServingDisabled bool
+
 	// Functions to all for a user to customize the values that will be injected.
 
 	// NewCache is the function that will create the cache to be used
@@ -211,18 +220,19 @@ func New(config *rest.Config, options Options) (Manager, error) {
 	stop := make(chan struct{})
 
 	return &controllerManager{
-		config:           config,
-		scheme:           options.Scheme,
-		errChan:          make(chan error),
-		cache:            cache,
-		fieldIndexes:     cache,
-		client:           writeObj,
-		recorderProvider: recorderProvider,
-		resourceLock:     resourceLock,
-		mapper:           mapper,
-		metricsListener:  metricsListener,
-		internalStop:     stop,
-		internalStopper:  stop,
+		config:                 config,
+		scheme:                 options.Scheme,
+		errChan:                make(chan error),
+		cache:                  cache,
+		fieldIndexes:           cache,
+		client:                 writeObj,
+		recorderProvider:       recorderProvider,
+		resourceLock:           resourceLock,
+		mapper:                 mapper,
+		metricsListener:        metricsListener,
+		metricsServingDisabled: options.MetricsServingDisabled,
+		internalStop:           stop,
+		internalStopper:        stop,
 	}, nil
 }