allow explicit disabling of metrics as an escape hatch.

Change-Id: I92895987d140e0e94eea3e4dea872c298d82babb

staging/src/k8s.io/component-base/metrics/collector.go

@@ -49,10 +49,10 @@ type StableCollector interface {
 // is a convenient assistant for custom collectors.
 // It is recommend that inherit BaseStableCollector when implementing custom collectors.
 type BaseStableCollector struct {
-	descriptors map[string]*Desc // stores all descriptors by pair<fqName, Desc>, these are collected from DescribeWithStability().
-	registrable map[string]*Desc // stores registrable descriptors by pair<fqName, Desc>, is a subset of descriptors.
-	hidden      map[string]*Desc // stores hidden descriptors by pair<fqName, Desc>, is a subset of descriptors.
-	self        StableCollector
+	descriptors  map[string]*Desc // stores all descriptors by pair<fqName, Desc>, these are collected from DescribeWithStability().
+	registerable map[string]*Desc // stores registerable descriptors by pair<fqName, Desc>, is a subset of descriptors.
+	hidden       map[string]*Desc // stores hidden descriptors by pair<fqName, Desc>, is a subset of descriptors.
+	self         StableCollector
 }
 
 // DescribeWithStability sends all descriptors to the provided channel.
@@ -64,7 +64,7 @@ func (bsc *BaseStableCollector) DescribeWithStability(ch chan<- *Desc) {
 // Describe sends all descriptors to the provided channel.
 // It intend to be called by prometheus registry.
 func (bsc *BaseStableCollector) Describe(ch chan<- *prometheus.Desc) {
-	for _, d := range bsc.registrable {
+	for _, d := range bsc.registerable {
 		ch <- d.toPrometheusDesc()
 	}
 }
@@ -128,11 +128,11 @@ func (bsc *BaseStableCollector) init(self StableCollector) {
 }
 
 func (bsc *BaseStableCollector) trackRegistrableDescriptor(d *Desc) {
-	if bsc.registrable == nil {
-		bsc.registrable = make(map[string]*Desc)
+	if bsc.registerable == nil {
+		bsc.registerable = make(map[string]*Desc)
 	}
 
-	bsc.registrable[d.fqName] = d
+	bsc.registerable[d.fqName] = d
 }
 
 func (bsc *BaseStableCollector) trackHiddenDescriptor(d *Desc) {
@@ -158,7 +158,7 @@ func (bsc *BaseStableCollector) Create(version *semver.Version, self StableColle
 		}
 	}
 
-	if len(bsc.registrable) > 0 {
+	if len(bsc.registerable) > 0 {
 		return true
 	}
 
@@ -173,7 +173,7 @@ func (bsc *BaseStableCollector) ClearState() {
 	}
 
 	bsc.descriptors = nil
-	bsc.registrable = nil
+	bsc.registerable = nil
 	bsc.hidden = nil
 	bsc.self = nil
 }

staging/src/k8s.io/component-base/metrics/metric.go

@@ -87,10 +87,24 @@ func (r *lazyMetric) lazyInit(self kubeCollector, fqName string) {
 	r.self = self
 }
 
-// determineDeprecationStatus figures out whether the lazy metric should be deprecated or not.
+// preprocessMetric figures out whether the lazy metric should be hidden or not.
 // This method takes a Version argument which should be the version of the binary in which
-// this code is currently being executed.
-func (r *lazyMetric) determineDeprecationStatus(version semver.Version) {
+// this code is currently being executed. A metric can be hidden under two conditions:
+//      1.  if the metric is deprecated and is outside the grace period (i.e. has been
+// 			deprecated for more than one release
+//		2. if the metric is manually disabled via a CLI flag.
+//
+// Disclaimer:  disabling a metric via a CLI flag has higher precedence than
+// 			  	deprecation and will override show-hidden-metrics for the explicitly
+//				disabled metric.
+func (r *lazyMetric) preprocessMetric(version semver.Version) {
+	disabledMetricsLock.RLock()
+	defer disabledMetricsLock.RUnlock()
+	// disabling metrics is higher in precedence than showing hidden metrics
+	if _, ok := disabledMetrics[r.fqName]; ok {
+		r.isHidden = true
+		return
+	}
 	selfVersion := r.self.DeprecatedVersion()
 	if selfVersion == nil {
 		return
@@ -99,6 +113,7 @@ func (r *lazyMetric) determineDeprecationStatus(version semver.Version) {
 		if selfVersion.LTE(version) {
 			r.isDeprecated = true
 		}
+
 		if ShouldShowHidden() {
 			klog.Warningf("Hidden metrics (%s) have been manually overridden, showing this very deprecated metric.", r.fqName)
 			return
@@ -126,7 +141,7 @@ func (r *lazyMetric) IsDeprecated() bool {
 // created.
 func (r *lazyMetric) Create(version *semver.Version) bool {
 	if version != nil {
-		r.determineDeprecationStatus(*version)
+		r.preprocessMetric(*version)
 	}
 	// let's not create if this metric is slated to be hidden
 	if r.IsHidden() {

staging/src/k8s.io/component-base/metrics/options.go

@@ -28,6 +28,7 @@ import (
 // Options has all parameters needed for exposing metrics from components
 type Options struct {
 	ShowHiddenMetricsForVersion string
+	DisabledMetrics             []string
 }
 
 // NewOptions returns default metrics options
@@ -56,12 +57,21 @@ func (o *Options) AddFlags(fs *pflag.FlagSet) {
 			"The format is <major>.<minor>, e.g.: '1.16'. "+
 			"The purpose of this format is make sure you have the opportunity to notice if the next release hides additional metrics, "+
 			"rather than being surprised when they are permanently removed in the release after that.")
+	fs.StringSliceVar(&o.DisabledMetrics,
+		"disabled-metrics",
+		o.DisabledMetrics,
+		"This flag provides an escape hatch for misbehaving metrics. "+
+			"You must provide the fully qualified metric name in order to disable it.")
 }
 
 // Apply applies parameters into global configuration of metrics.
 func (o *Options) Apply() {
 	if o != nil && len(o.ShowHiddenMetricsForVersion) > 0 {
 		SetShowHidden()
+		// set disabled metrics
+		for _, metricName := range o.DisabledMetrics {
+			SetDisabledMetric(metricName)
+		}
 	}
 }
 

staging/src/k8s.io/component-base/metrics/registry.go

@@ -30,10 +30,12 @@ import (
 )
 
 var (
-	showHiddenOnce sync.Once
-	showHidden     atomic.Value
-	registries     []*kubeRegistry // stores all registries created by NewKubeRegistry()
-	registriesLock sync.RWMutex
+	showHiddenOnce      sync.Once
+	disabledMetricsLock sync.RWMutex
+	showHidden          atomic.Value
+	registries          []*kubeRegistry // stores all registries created by NewKubeRegistry()
+	registriesLock      sync.RWMutex
+	disabledMetrics     = map[string]struct{}{}
 )
 
 // shouldHide be used to check if a specific metric with deprecated version should be hidden
@@ -61,6 +63,12 @@ func ValidateShowHiddenMetricsVersion(v string) []error {
 	return nil
 }
 
+func SetDisabledMetric(name string) {
+	disabledMetricsLock.Lock()
+	defer disabledMetricsLock.Unlock()
+	disabledMetrics[name] = struct{}{}
+}
+
 // SetShowHidden will enable showing hidden metrics. This will no-opt
 // after the initial call
 func SetShowHidden() {

staging/src/k8s.io/component-base/metrics/registry_test.go

@@ -515,3 +515,39 @@ func TestRegistryReset(t *testing.T) {
 		t.Fatal(err)
 	}
 }
+
+func TestDisabledMetrics(t *testing.T) {
+	SetDisabledMetric("should_be_disabled")
+	currentVersion := apimachineryversion.Info{
+		Major:      "1",
+		Minor:      "17",
+		GitVersion: "v1.17.1-alpha-1.12345",
+	}
+	registry := newKubeRegistry(currentVersion)
+	disabledMetric := NewCounterVec(&CounterOpts{
+		Name: "should_be_disabled",
+		Help: "this metric should be disabled",
+	}, []string{"label"})
+	// gauges cannot be reset
+	enabledMetric := NewGauge(&GaugeOpts{
+		Name: "should_be_enabled",
+		Help: "this metric should not be disabled",
+	})
+
+	registry.MustRegister(disabledMetric)
+	registry.MustRegister(enabledMetric)
+	disabledMetric.WithLabelValues("one").Inc()
+	disabledMetric.WithLabelValues("two").Inc()
+	disabledMetric.WithLabelValues("two").Inc()
+	enabledMetric.Inc()
+
+	enabledMetricOutput := `
+        # HELP should_be_enabled [ALPHA] this metric should not be disabled
+        # TYPE should_be_enabled gauge
+        should_be_enabled 1
+`
+
+	if err := testutil.GatherAndCompare(registry, strings.NewReader(enabledMetricOutput), "should_be_disabled", "should_be_enabled"); err != nil {
+		t.Fatal(err)
+	}
+}