From e1e022f54841f897c4afb3ef00b9b13780543e63 Mon Sep 17 00:00:00 2001
From: Mike Spreitzer <mspreitz@us.ibm.com>
Date: Thu, 10 Sep 2020 01:17:01 -0400
Subject: [PATCH 1/7] Start drafting SamplingHistogram

This covers SamplingHistogram but not SamplingHistogramVec (because
the vec support of prometheus is not public).
---
 .../sampling-histogram.go                     | 120 ++++++++++++++++++
 .../sampling-histogram_test.go                | 120 ++++++++++++++++++
 2 files changed, 240 insertions(+)
 create mode 100644 staging/src/k8s.io/component-base/metrics/prometheus_extension/sampling-histogram.go
 create mode 100644 staging/src/k8s.io/component-base/metrics/prometheus_extension/sampling-histogram_test.go

diff --git a/staging/src/k8s.io/component-base/metrics/prometheus_extension/sampling-histogram.go b/staging/src/k8s.io/component-base/metrics/prometheus_extension/sampling-histogram.go
new file mode 100644
index 000000000000..ce5b3e8459ca
--- /dev/null
+++ b/staging/src/k8s.io/component-base/metrics/prometheus_extension/sampling-histogram.go
@@ -0,0 +1,120 @@
+/*
+Copyright 2020 Mike Spreitzer.
+
+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 prometheus_extension
+
+import (
+	"sync"
+	"time"
+
+	"github.com/prometheus/client_golang/prometheus"
+	dto "github.com/prometheus/client_model/go"
+	"k8s.io/utils/clock"
+)
+
+// A SamplingHistogram samples the values of a float64 variable at a
+// configured rate.  The samples contribute to a Histogram.
+type SamplingHistogram interface {
+	prometheus.Metric
+	prometheus.Collector
+
+	// Sets the variable to the given value.
+	Set(float64)
+}
+
+type SamplingHistogramOpts struct {
+	prometheus.HistogramOpts
+
+	// The initial value of the variable
+	InitialValue float64
+
+	// The variable is sampled once every this often
+	SamplingPeriod time.Duration
+}
+
+func NewSamplingHistogram(opts SamplingHistogramOpts) SamplingHistogram {
+	return NewTestableSamplingHistogram(clock.RealClock{}, opts)
+}
+
+func NewTestableSamplingHistogram(clock clock.Clock, opts SamplingHistogramOpts) SamplingHistogram {
+	desc := prometheus.NewDesc(
+		prometheus.BuildFQName(opts.Namespace, opts.Subsystem, opts.Name),
+		opts.Help,
+		nil,
+		opts.ConstLabels,
+	)
+	return newSamplingHistogram(clock, desc, opts)
+}
+
+func newSamplingHistogram(clock clock.Clock, desc *prometheus.Desc, opts SamplingHistogramOpts, labelValues ...string) SamplingHistogram {
+	return &samplingHistogram{
+		samplingPeriod:  opts.SamplingPeriod,
+		histogram:       prometheus.NewHistogram(opts.HistogramOpts),
+		clock:           clock,
+		lastSampleIndex: clock.Now().UnixNano() / int64(opts.SamplingPeriod),
+		value:           opts.InitialValue,
+	}
+}
+
+type samplingHistogram struct {
+	samplingPeriod time.Duration
+	histogram      prometheus.Histogram
+	clock          clock.Clock
+	lock           sync.Mutex
+
+	// identifies the last sampling period completed
+	lastSampleIndex int64
+	value           float64
+}
+
+var _ SamplingHistogram = &samplingHistogram{}
+
+func (sh *samplingHistogram) Set(newValue float64) {
+	sh.Update(func(float64) float64 { return newValue })
+}
+
+func (sh *samplingHistogram) Update(updateFn func(float64) float64) {
+	oldValue, numSamples := func() (float64, int64) {
+		sh.lock.Lock()
+		defer sh.lock.Unlock()
+		newSampleIndex := sh.clock.Now().UnixNano() / int64(sh.samplingPeriod)
+		deltaIndex := newSampleIndex - sh.lastSampleIndex
+		sh.lastSampleIndex = newSampleIndex
+		oldValue := sh.value
+		sh.value = updateFn(sh.value)
+		return oldValue, deltaIndex
+	}()
+	for i := int64(0); i < numSamples; i++ {
+		sh.histogram.Observe(oldValue)
+	}
+}
+
+func (sh *samplingHistogram) Desc() *prometheus.Desc {
+	return sh.histogram.Desc()
+}
+
+func (sh *samplingHistogram) Write(dest *dto.Metric) error {
+	return sh.histogram.Write(dest)
+}
+
+func (sh *samplingHistogram) Describe(ch chan<- *prometheus.Desc) {
+	sh.histogram.Describe(ch)
+}
+
+func (sh *samplingHistogram) Collect(ch chan<- prometheus.Metric) {
+	sh.Update(func(value float64) float64 { return value })
+	sh.histogram.Collect(ch)
+}
diff --git a/staging/src/k8s.io/component-base/metrics/prometheus_extension/sampling-histogram_test.go b/staging/src/k8s.io/component-base/metrics/prometheus_extension/sampling-histogram_test.go
new file mode 100644
index 000000000000..76150225c77c
--- /dev/null
+++ b/staging/src/k8s.io/component-base/metrics/prometheus_extension/sampling-histogram_test.go
@@ -0,0 +1,120 @@
+/*
+Copyright 2020 Mike Spreitzer.
+
+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 prometheus_extension
+
+import (
+	"testing"
+	"time"
+
+	"github.com/prometheus/client_golang/prometheus"
+	dto "github.com/prometheus/client_model/go"
+	testclock "k8s.io/utils/clock/testing"
+)
+
+func TestSamplingHistogram(t *testing.T) {
+	clk := testclock.NewFakeClock(time.Unix(time.Now().Unix(), 999999990))
+	sh := NewTestableSamplingHistogram(clk, SamplingHistogramOpts{
+		HistogramOpts: prometheus.HistogramOpts{
+			Namespace:   "test",
+			Subsystem:   "func",
+			Name:        "one",
+			Help:        "a helpful string",
+			ConstLabels: map[string]string{"l1": "v1", "l2": "v2"},
+			Buckets:     []float64{0, 1, 2},
+		},
+		InitialValue:   1,
+		SamplingPeriod: time.Second,
+	})
+	expectHistogram(t, "After creation", sh, 0, 0, 0, 0)
+	sh.Set(2)
+	expectHistogram(t, "After initial Set", sh, 0, 0, 0, 0)
+	clk.Step(9 * time.Nanosecond)
+	expectHistogram(t, "Just before the end of the first sampling period", sh, 0, 0, 0, 0)
+	clk.Step(1 * time.Nanosecond)
+	expectHistogram(t, "At the end of the first sampling period", sh, 0, 0, 1, 1)
+	clk.Step(1 * time.Nanosecond)
+	expectHistogram(t, "Barely into second sampling period", sh, 0, 0, 1, 1)
+	sh.Set(-0.5)
+	sh.Set(0.5)
+	clk.Step(999999998 * time.Nanosecond)
+	expectHistogram(t, "Just before the end of second sampling period", sh, 0, 0, 1, 1)
+	clk.Step(1 * time.Nanosecond)
+	expectHistogram(t, "At the end of second sampling period", sh, 0, 1, 2, 2)
+}
+
+func expectHistogram(t *testing.T, when string, sh SamplingHistogram, buckets ...uint64) {
+	metrics := make(chan prometheus.Metric, 2)
+	sh.Collect(metrics)
+	var dtom dto.Metric
+	select {
+	case metric := <-metrics:
+		metric.Write(&dtom)
+	default:
+		t.Errorf("%s, zero Metrics collected", when)
+	}
+	select {
+	case metric := <-metrics:
+		t.Errorf("%s, collected more than one Metric; second Metric = %#+v", when, metric)
+	default:
+	}
+	missingLabels := map[string]string{"l1": "v1", "l2": "v2"}
+	for _, lp := range dtom.Label {
+		if lp == nil || lp.Name == nil || lp.Value == nil {
+			continue
+		}
+		if val, ok := missingLabels[*(lp.Name)]; ok {
+			if val != *(lp.Value) {
+				t.Errorf("%s, found label named %q with value %q instead of %q", when, *(lp.Name), *(lp.Value), val)
+			}
+		} else {
+			t.Errorf("%s, got unexpected label name %q", when, *(lp.Name))
+		}
+		delete(missingLabels, *(lp.Name))
+	}
+	if len(missingLabels) > 0 {
+		t.Errorf("%s, missed labels %#+v", when, missingLabels)
+	}
+	if dtom.Histogram == nil {
+		t.Errorf("%s, Collect returned a Metric without a Histogram: %#+v", when, dtom)
+	}
+	mh := dtom.Histogram
+	if len(mh.Bucket) != len(buckets)-1 {
+		t.Errorf("%s, expected %d buckets but got %d: %#+v", when, len(buckets)-1, len(mh.Bucket), mh.Bucket)
+	}
+	if mh.SampleCount == nil {
+		t.Errorf("%s, got Histogram with nil SampleCount", when)
+	}
+	if *(mh.SampleCount) != buckets[len(mh.Bucket)] {
+		t.Errorf("%s, SampleCount=%d but expected %d", when, *(mh.SampleCount), buckets[len(mh.Bucket)])
+	}
+	for i, mhBucket := range mh.Bucket {
+		if mhBucket == nil {
+			t.Errorf("%s, bucket %d was nil", when, i)
+		}
+		if mhBucket.UpperBound == nil || mhBucket.CumulativeCount == nil {
+			t.Errorf("%s, bucket %d had nil bound or count", when, i)
+		}
+		ub := float64(i)
+		if ub != *(mhBucket.UpperBound) {
+			t.Errorf("%s, bucket %d's upper bound was %v", when, i, *(mhBucket.UpperBound))
+		}
+		expectedCount := buckets[i]
+		if expectedCount != *(mhBucket.CumulativeCount) {
+			t.Errorf("%s, bucket %d's count was %d rather than %d", when, i, mhBucket.CumulativeCount, expectedCount)
+		}
+	}
+}

From 93ef341029310a5b3bf743a051cef3ada5fdd88e Mon Sep 17 00:00:00 2001
From: Mike Spreitzer <mspreitz@us.ibm.com>
Date: Thu, 10 Sep 2020 02:24:13 -0400
Subject: [PATCH 2/7] Added wrapper for SamplingHistogram

---
 .../src/k8s.io/component-base/metrics/opts.go | 52 +++++++++++++
 .../sampling-histogram.go                     | 11 ++-
 .../sampling-histogram_test.go                |  2 +-
 .../metrics/sampling-histogram.go             | 75 +++++++++++++++++++
 .../k8s.io/component-base/metrics/wrappers.go |  9 ++-
 5 files changed, 144 insertions(+), 5 deletions(-)
 create mode 100644 staging/src/k8s.io/component-base/metrics/sampling-histogram.go

diff --git a/staging/src/k8s.io/component-base/metrics/opts.go b/staging/src/k8s.io/component-base/metrics/opts.go
index 906050c7f78a..f61f8d0d9479 100644
--- a/staging/src/k8s.io/component-base/metrics/opts.go
+++ b/staging/src/k8s.io/component-base/metrics/opts.go
@@ -22,6 +22,7 @@ import (
 	"time"
 
 	"github.com/prometheus/client_golang/prometheus"
+	promext "k8s.io/component-base/metrics/prometheus_extension"
 )
 
 // KubeOpts is superset struct for prometheus.Opts. The prometheus Opts structure
@@ -180,6 +181,57 @@ func (o *HistogramOpts) toPromHistogramOpts() prometheus.HistogramOpts {
 	}
 }
 
+// SamplingHistogramOpts bundles the options for creating a SamplingHistogram metric. It is
+// mandatory to set Name to a non-empty string. All other fields are optional
+// and can safely be left at their zero value, although it is strongly
+// encouraged to set a Help string.
+type SamplingHistogramOpts struct {
+	Namespace         string
+	Subsystem         string
+	Name              string
+	Help              string
+	ConstLabels       map[string]string
+	Buckets           []float64
+	InitialValue      float64
+	SamplingPeriod    time.Duration
+	DeprecatedVersion string
+	deprecateOnce     sync.Once
+	annotateOnce      sync.Once
+	StabilityLevel    StabilityLevel
+}
+
+// Modify help description on the metric description.
+func (o *SamplingHistogramOpts) markDeprecated() {
+	o.deprecateOnce.Do(func() {
+		o.Help = fmt.Sprintf("(Deprecated since %v) %v", o.DeprecatedVersion, o.Help)
+	})
+}
+
+// annotateStabilityLevel annotates help description on the metric description with the stability level
+// of the metric
+func (o *SamplingHistogramOpts) annotateStabilityLevel() {
+	o.annotateOnce.Do(func() {
+		o.Help = fmt.Sprintf("[%v] %v", o.StabilityLevel, o.Help)
+	})
+}
+
+// convenience function to allow easy transformation to the prometheus
+// counterpart. This will do more once we have a proper label abstraction
+func (o *SamplingHistogramOpts) toPromSamplingHistogramOpts() promext.SamplingHistogramOpts {
+	return promext.SamplingHistogramOpts{
+		HistogramOpts: prometheus.HistogramOpts{
+			Namespace:   o.Namespace,
+			Subsystem:   o.Subsystem,
+			Name:        o.Name,
+			Help:        o.Help,
+			ConstLabels: o.ConstLabels,
+			Buckets:     o.Buckets,
+		},
+		InitialValue:   o.InitialValue,
+		SamplingPeriod: o.SamplingPeriod,
+	}
+}
+
 // SummaryOpts bundles the options for creating a Summary metric. It is
 // mandatory to set Name to a non-empty string. While all other fields are
 // optional and can safely be left at their zero value, it is recommended to set
diff --git a/staging/src/k8s.io/component-base/metrics/prometheus_extension/sampling-histogram.go b/staging/src/k8s.io/component-base/metrics/prometheus_extension/sampling-histogram.go
index ce5b3e8459ca..518547b10e02 100644
--- a/staging/src/k8s.io/component-base/metrics/prometheus_extension/sampling-histogram.go
+++ b/staging/src/k8s.io/component-base/metrics/prometheus_extension/sampling-histogram.go
@@ -31,8 +31,11 @@ type SamplingHistogram interface {
 	prometheus.Metric
 	prometheus.Collector
 
-	// Sets the variable to the given value.
+	// Set the variable to the given value.
 	Set(float64)
+
+	// Add the given change to the variable
+	Add(float64)
 }
 
 type SamplingHistogramOpts struct {
@@ -86,6 +89,10 @@ func (sh *samplingHistogram) Set(newValue float64) {
 	sh.Update(func(float64) float64 { return newValue })
 }
 
+func (sh *samplingHistogram) Add(delta float64) {
+	sh.Update(func(oldValue float64) float64 { return oldValue + delta })
+}
+
 func (sh *samplingHistogram) Update(updateFn func(float64) float64) {
 	oldValue, numSamples := func() (float64, int64) {
 		sh.lock.Lock()
@@ -115,6 +122,6 @@ func (sh *samplingHistogram) Describe(ch chan<- *prometheus.Desc) {
 }
 
 func (sh *samplingHistogram) Collect(ch chan<- prometheus.Metric) {
-	sh.Update(func(value float64) float64 { return value })
+	sh.Add(0)
 	sh.histogram.Collect(ch)
 }
diff --git a/staging/src/k8s.io/component-base/metrics/prometheus_extension/sampling-histogram_test.go b/staging/src/k8s.io/component-base/metrics/prometheus_extension/sampling-histogram_test.go
index 76150225c77c..71e25d0466e1 100644
--- a/staging/src/k8s.io/component-base/metrics/prometheus_extension/sampling-histogram_test.go
+++ b/staging/src/k8s.io/component-base/metrics/prometheus_extension/sampling-histogram_test.go
@@ -49,7 +49,7 @@ func TestSamplingHistogram(t *testing.T) {
 	clk.Step(1 * time.Nanosecond)
 	expectHistogram(t, "Barely into second sampling period", sh, 0, 0, 1, 1)
 	sh.Set(-0.5)
-	sh.Set(0.5)
+	sh.Add(1)
 	clk.Step(999999998 * time.Nanosecond)
 	expectHistogram(t, "Just before the end of second sampling period", sh, 0, 0, 1, 1)
 	clk.Step(1 * time.Nanosecond)
diff --git a/staging/src/k8s.io/component-base/metrics/sampling-histogram.go b/staging/src/k8s.io/component-base/metrics/sampling-histogram.go
new file mode 100644
index 000000000000..42f16590e89d
--- /dev/null
+++ b/staging/src/k8s.io/component-base/metrics/sampling-histogram.go
@@ -0,0 +1,75 @@
+/*
+Copyright 2019 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 metrics
+
+import (
+	"github.com/blang/semver"
+
+	promext "k8s.io/component-base/metrics/prometheus_extension"
+)
+
+// SamplingHistogram is our internal representation for our wrapping struct around prometheus
+// sampling histograms. SamplingHistogram implements both kubeCollector and SimpleGaugeMetric
+type SamplingHistogram struct {
+	SimpleGaugeMetric
+	*SamplingHistogramOpts
+	lazyMetric
+	selfCollector
+}
+
+var _ kubeCollector = &SamplingHistogram{}
+var _ SimpleGaugeMetric = &SamplingHistogram{}
+
+// NewSamplingHistogram returns an object which is SamplingHistogram-like. However, nothing
+// will be measured until the histogram is registered somewhere.
+func NewSamplingHistogram(opts *SamplingHistogramOpts) *SamplingHistogram {
+	opts.StabilityLevel.setDefaults()
+
+	h := &SamplingHistogram{
+		SamplingHistogramOpts: opts,
+		lazyMetric:            lazyMetric{},
+	}
+	h.setPrometheusSamplingHistogram(noopMetric{})
+	h.lazyInit(h, BuildFQName(opts.Namespace, opts.Subsystem, opts.Name))
+	return h
+}
+
+// setPrometheusSamplingHistogram sets the underlying KubeGauge object, i.e. the thing that does the measurement.
+func (h *SamplingHistogram) setPrometheusSamplingHistogram(histogram promext.SamplingHistogram) {
+	h.SimpleGaugeMetric = histogram
+	h.initSelfCollection(histogram)
+}
+
+// DeprecatedVersion returns a pointer to the Version or nil
+func (h *SamplingHistogram) DeprecatedVersion() *semver.Version {
+	return parseSemver(h.SamplingHistogramOpts.DeprecatedVersion)
+}
+
+// initializeMetric invokes the actual prometheus.SamplingHistogram object instantiation
+// and stores a reference to it
+func (h *SamplingHistogram) initializeMetric() {
+	h.SamplingHistogramOpts.annotateStabilityLevel()
+	// this actually creates the underlying prometheus gauge.
+	h.setPrometheusSamplingHistogram(promext.NewSamplingHistogram(h.SamplingHistogramOpts.toPromSamplingHistogramOpts()))
+}
+
+// initializeDeprecatedMetric invokes the actual prometheus.SamplingHistogram object instantiation
+// but modifies the Help description prior to object instantiation.
+func (h *SamplingHistogram) initializeDeprecatedMetric() {
+	h.SamplingHistogramOpts.markDeprecated()
+	h.initializeMetric()
+}
diff --git a/staging/src/k8s.io/component-base/metrics/wrappers.go b/staging/src/k8s.io/component-base/metrics/wrappers.go
index 6ae8a458acb7..00d12515642c 100644
--- a/staging/src/k8s.io/component-base/metrics/wrappers.go
+++ b/staging/src/k8s.io/component-base/metrics/wrappers.go
@@ -55,12 +55,17 @@ type CounterVecMetric interface {
 	With(prometheus.Labels) CounterMetric
 }
 
+// SimpleGaugeMetric is an interface which defines a small subset of the interface provided by prometheus.Gauge
+type SimpleGaugeMetric interface {
+	Set(float64)
+	Add(float64)
+}
+
 // GaugeMetric is an interface which defines a subset of the interface provided by prometheus.Gauge
 type GaugeMetric interface {
-	Set(float64)
+	SimpleGaugeMetric
 	Inc()
 	Dec()
-	Add(float64)
 	Write(out *dto.Metric) error
 	SetToCurrentTime()
 }

From c33889941fea720df11ea5ca5ecc5697702d9e27 Mon Sep 17 00:00:00 2001
From: Mike Spreitzer <mspreitz@us.ibm.com>
Date: Thu, 10 Sep 2020 03:10:05 -0400
Subject: [PATCH 3/7] update bazel and vendor/modules.txt

---
 .../src/k8s.io/component-base/metrics/BUILD   |  3 ++
 .../metrics/prometheus_extension/BUILD        | 39 +++++++++++++++++++
 vendor/modules.txt                            |  1 +
 3 files changed, 43 insertions(+)
 create mode 100644 staging/src/k8s.io/component-base/metrics/prometheus_extension/BUILD

diff --git a/staging/src/k8s.io/component-base/metrics/BUILD b/staging/src/k8s.io/component-base/metrics/BUILD
index b75763c4c1bd..31055f227b52 100644
--- a/staging/src/k8s.io/component-base/metrics/BUILD
+++ b/staging/src/k8s.io/component-base/metrics/BUILD
@@ -15,6 +15,7 @@ go_library(
         "opts.go",
         "processstarttime.go",
         "registry.go",
+        "sampling-histogram.go",
         "summary.go",
         "value.go",
         "version.go",
@@ -26,6 +27,7 @@ go_library(
     visibility = ["//visibility:public"],
     deps = [
         "//staging/src/k8s.io/apimachinery/pkg/version:go_default_library",
+        "//staging/src/k8s.io/component-base/metrics/prometheus_extension:go_default_library",
         "//staging/src/k8s.io/component-base/version:go_default_library",
         "//vendor/github.com/blang/semver:go_default_library",
         "//vendor/github.com/prometheus/client_golang/prometheus:go_default_library",
@@ -79,6 +81,7 @@ filegroup(
         "//staging/src/k8s.io/component-base/metrics/prometheus/restclient:all-srcs",
         "//staging/src/k8s.io/component-base/metrics/prometheus/version:all-srcs",
         "//staging/src/k8s.io/component-base/metrics/prometheus/workqueue:all-srcs",
+        "//staging/src/k8s.io/component-base/metrics/prometheus_extension:all-srcs",
         "//staging/src/k8s.io/component-base/metrics/testutil:all-srcs",
     ],
     tags = ["automanaged"],
diff --git a/staging/src/k8s.io/component-base/metrics/prometheus_extension/BUILD b/staging/src/k8s.io/component-base/metrics/prometheus_extension/BUILD
new file mode 100644
index 000000000000..b07ce054c3c2
--- /dev/null
+++ b/staging/src/k8s.io/component-base/metrics/prometheus_extension/BUILD
@@ -0,0 +1,39 @@
+load("@io_bazel_rules_go//go:def.bzl", "go_library", "go_test")
+
+go_library(
+    name = "go_default_library",
+    srcs = ["sampling-histogram.go"],
+    importmap = "k8s.io/kubernetes/vendor/k8s.io/component-base/metrics/prometheus_extension",
+    importpath = "k8s.io/component-base/metrics/prometheus_extension",
+    visibility = ["//visibility:public"],
+    deps = [
+        "//vendor/github.com/prometheus/client_golang/prometheus:go_default_library",
+        "//vendor/github.com/prometheus/client_model/go:go_default_library",
+        "//vendor/k8s.io/utils/clock:go_default_library",
+    ],
+)
+
+go_test(
+    name = "go_default_test",
+    srcs = ["sampling-histogram_test.go"],
+    embed = [":go_default_library"],
+    deps = [
+        "//vendor/github.com/prometheus/client_golang/prometheus:go_default_library",
+        "//vendor/github.com/prometheus/client_model/go:go_default_library",
+        "//vendor/k8s.io/utils/clock/testing:go_default_library",
+    ],
+)
+
+filegroup(
+    name = "package-srcs",
+    srcs = glob(["**"]),
+    tags = ["automanaged"],
+    visibility = ["//visibility:private"],
+)
+
+filegroup(
+    name = "all-srcs",
+    srcs = [":package-srcs"],
+    tags = ["automanaged"],
+    visibility = ["//visibility:public"],
+)
diff --git a/vendor/modules.txt b/vendor/modules.txt
index ac972aa186a3..ed4527e0fc99 100644
--- a/vendor/modules.txt
+++ b/vendor/modules.txt
@@ -2171,6 +2171,7 @@ k8s.io/component-base/metrics/prometheus/ratelimiter
 k8s.io/component-base/metrics/prometheus/restclient
 k8s.io/component-base/metrics/prometheus/version
 k8s.io/component-base/metrics/prometheus/workqueue
+k8s.io/component-base/metrics/prometheus_extension
 k8s.io/component-base/metrics/testutil
 k8s.io/component-base/term
 k8s.io/component-base/version

From 32c82c10c0998c2ce0cb26d71ac7ef940cb23594 Mon Sep 17 00:00:00 2001
From: Mike Spreitzer <mspreitz@us.ibm.com>
Date: Fri, 11 Sep 2020 02:14:03 -0400
Subject: [PATCH 4/7] Fixed lint, constrained SamplingPeriod > 0

---
 .../src/k8s.io/component-base/metrics/BUILD   |  4 ++--
 .../src/k8s.io/component-base/metrics/opts.go |  2 +-
 .../BUILD                                     |  4 ++--
 .../sampling-histogram.go                     | 24 +++++++++++++------
 .../sampling-histogram_test.go                |  7 ++++--
 .../metrics/sampling-histogram.go             |  2 +-
 vendor/modules.txt                            |  2 +-
 7 files changed, 29 insertions(+), 16 deletions(-)
 rename staging/src/k8s.io/component-base/metrics/{prometheus_extension => prometheusextension}/BUILD (91%)
 rename staging/src/k8s.io/component-base/metrics/{prometheus_extension => prometheusextension}/sampling-histogram.go (79%)
 rename staging/src/k8s.io/component-base/metrics/{prometheus_extension => prometheusextension}/sampling-histogram_test.go (95%)

diff --git a/staging/src/k8s.io/component-base/metrics/BUILD b/staging/src/k8s.io/component-base/metrics/BUILD
index 31055f227b52..27522aae83f8 100644
--- a/staging/src/k8s.io/component-base/metrics/BUILD
+++ b/staging/src/k8s.io/component-base/metrics/BUILD
@@ -27,7 +27,7 @@ go_library(
     visibility = ["//visibility:public"],
     deps = [
         "//staging/src/k8s.io/apimachinery/pkg/version:go_default_library",
-        "//staging/src/k8s.io/component-base/metrics/prometheus_extension:go_default_library",
+        "//staging/src/k8s.io/component-base/metrics/prometheusextension:go_default_library",
         "//staging/src/k8s.io/component-base/version:go_default_library",
         "//vendor/github.com/blang/semver:go_default_library",
         "//vendor/github.com/prometheus/client_golang/prometheus:go_default_library",
@@ -81,7 +81,7 @@ filegroup(
         "//staging/src/k8s.io/component-base/metrics/prometheus/restclient:all-srcs",
         "//staging/src/k8s.io/component-base/metrics/prometheus/version:all-srcs",
         "//staging/src/k8s.io/component-base/metrics/prometheus/workqueue:all-srcs",
-        "//staging/src/k8s.io/component-base/metrics/prometheus_extension:all-srcs",
+        "//staging/src/k8s.io/component-base/metrics/prometheusextension:all-srcs",
         "//staging/src/k8s.io/component-base/metrics/testutil:all-srcs",
     ],
     tags = ["automanaged"],
diff --git a/staging/src/k8s.io/component-base/metrics/opts.go b/staging/src/k8s.io/component-base/metrics/opts.go
index f61f8d0d9479..f77c4788f869 100644
--- a/staging/src/k8s.io/component-base/metrics/opts.go
+++ b/staging/src/k8s.io/component-base/metrics/opts.go
@@ -22,7 +22,7 @@ import (
 	"time"
 
 	"github.com/prometheus/client_golang/prometheus"
-	promext "k8s.io/component-base/metrics/prometheus_extension"
+	promext "k8s.io/component-base/metrics/prometheusextension"
 )
 
 // KubeOpts is superset struct for prometheus.Opts. The prometheus Opts structure
diff --git a/staging/src/k8s.io/component-base/metrics/prometheus_extension/BUILD b/staging/src/k8s.io/component-base/metrics/prometheusextension/BUILD
similarity index 91%
rename from staging/src/k8s.io/component-base/metrics/prometheus_extension/BUILD
rename to staging/src/k8s.io/component-base/metrics/prometheusextension/BUILD
index b07ce054c3c2..7d515560cf32 100644
--- a/staging/src/k8s.io/component-base/metrics/prometheus_extension/BUILD
+++ b/staging/src/k8s.io/component-base/metrics/prometheusextension/BUILD
@@ -3,8 +3,8 @@ load("@io_bazel_rules_go//go:def.bzl", "go_library", "go_test")
 go_library(
     name = "go_default_library",
     srcs = ["sampling-histogram.go"],
-    importmap = "k8s.io/kubernetes/vendor/k8s.io/component-base/metrics/prometheus_extension",
-    importpath = "k8s.io/component-base/metrics/prometheus_extension",
+    importmap = "k8s.io/kubernetes/vendor/k8s.io/component-base/metrics/prometheusextension",
+    importpath = "k8s.io/component-base/metrics/prometheusextension",
     visibility = ["//visibility:public"],
     deps = [
         "//vendor/github.com/prometheus/client_golang/prometheus:go_default_library",
diff --git a/staging/src/k8s.io/component-base/metrics/prometheus_extension/sampling-histogram.go b/staging/src/k8s.io/component-base/metrics/prometheusextension/sampling-histogram.go
similarity index 79%
rename from staging/src/k8s.io/component-base/metrics/prometheus_extension/sampling-histogram.go
rename to staging/src/k8s.io/component-base/metrics/prometheusextension/sampling-histogram.go
index 518547b10e02..5d590ac88472 100644
--- a/staging/src/k8s.io/component-base/metrics/prometheus_extension/sampling-histogram.go
+++ b/staging/src/k8s.io/component-base/metrics/prometheusextension/sampling-histogram.go
@@ -14,9 +14,10 @@ See the License for the specific language governing permissions and
 limitations under the License.
 */
 
-package prometheus_extension
+package prometheusextension
 
 import (
+	"fmt"
 	"sync"
 	"time"
 
@@ -38,21 +39,27 @@ type SamplingHistogram interface {
 	Add(float64)
 }
 
+// SamplingHistogramOpts bundles the options for creating a
+// SamplingHistogram metric.  This builds on the options for creating
+// a Histogram metric.
 type SamplingHistogramOpts struct {
 	prometheus.HistogramOpts
 
-	// The initial value of the variable
+	// The initial value of the variable.
 	InitialValue float64
 
-	// The variable is sampled once every this often
+	// The variable is sampled once every this often.
+	// Must be set to a positive value.
 	SamplingPeriod time.Duration
 }
 
-func NewSamplingHistogram(opts SamplingHistogramOpts) SamplingHistogram {
+// NewSamplingHistogram creates a new SamplingHistogram
+func NewSamplingHistogram(opts SamplingHistogramOpts) (SamplingHistogram, error) {
 	return NewTestableSamplingHistogram(clock.RealClock{}, opts)
 }
 
-func NewTestableSamplingHistogram(clock clock.Clock, opts SamplingHistogramOpts) SamplingHistogram {
+// NewTestableSamplingHistogram creates a SamplingHistogram that uses a mockable clock
+func NewTestableSamplingHistogram(clock clock.Clock, opts SamplingHistogramOpts) (SamplingHistogram, error) {
 	desc := prometheus.NewDesc(
 		prometheus.BuildFQName(opts.Namespace, opts.Subsystem, opts.Name),
 		opts.Help,
@@ -62,14 +69,17 @@ func NewTestableSamplingHistogram(clock clock.Clock, opts SamplingHistogramOpts)
 	return newSamplingHistogram(clock, desc, opts)
 }
 
-func newSamplingHistogram(clock clock.Clock, desc *prometheus.Desc, opts SamplingHistogramOpts, labelValues ...string) SamplingHistogram {
+func newSamplingHistogram(clock clock.Clock, desc *prometheus.Desc, opts SamplingHistogramOpts, labelValues ...string) (SamplingHistogram, error) {
+	if opts.SamplingPeriod <= 0 {
+		return nil, fmt.Errorf("the given sampling period was %v but must be positive", opts.SamplingPeriod)
+	}
 	return &samplingHistogram{
 		samplingPeriod:  opts.SamplingPeriod,
 		histogram:       prometheus.NewHistogram(opts.HistogramOpts),
 		clock:           clock,
 		lastSampleIndex: clock.Now().UnixNano() / int64(opts.SamplingPeriod),
 		value:           opts.InitialValue,
-	}
+	}, nil
 }
 
 type samplingHistogram struct {
diff --git a/staging/src/k8s.io/component-base/metrics/prometheus_extension/sampling-histogram_test.go b/staging/src/k8s.io/component-base/metrics/prometheusextension/sampling-histogram_test.go
similarity index 95%
rename from staging/src/k8s.io/component-base/metrics/prometheus_extension/sampling-histogram_test.go
rename to staging/src/k8s.io/component-base/metrics/prometheusextension/sampling-histogram_test.go
index 71e25d0466e1..c27765f0b15a 100644
--- a/staging/src/k8s.io/component-base/metrics/prometheus_extension/sampling-histogram_test.go
+++ b/staging/src/k8s.io/component-base/metrics/prometheusextension/sampling-histogram_test.go
@@ -14,7 +14,7 @@ See the License for the specific language governing permissions and
 limitations under the License.
 */
 
-package prometheus_extension
+package prometheusextension
 
 import (
 	"testing"
@@ -27,7 +27,7 @@ import (
 
 func TestSamplingHistogram(t *testing.T) {
 	clk := testclock.NewFakeClock(time.Unix(time.Now().Unix(), 999999990))
-	sh := NewTestableSamplingHistogram(clk, SamplingHistogramOpts{
+	sh, err := NewTestableSamplingHistogram(clk, SamplingHistogramOpts{
 		HistogramOpts: prometheus.HistogramOpts{
 			Namespace:   "test",
 			Subsystem:   "func",
@@ -39,6 +39,9 @@ func TestSamplingHistogram(t *testing.T) {
 		InitialValue:   1,
 		SamplingPeriod: time.Second,
 	})
+	if sh == nil || err != nil {
+		t.Errorf("Creation failed; err=%s", err.Error())
+	}
 	expectHistogram(t, "After creation", sh, 0, 0, 0, 0)
 	sh.Set(2)
 	expectHistogram(t, "After initial Set", sh, 0, 0, 0, 0)
diff --git a/staging/src/k8s.io/component-base/metrics/sampling-histogram.go b/staging/src/k8s.io/component-base/metrics/sampling-histogram.go
index 42f16590e89d..1492838a4460 100644
--- a/staging/src/k8s.io/component-base/metrics/sampling-histogram.go
+++ b/staging/src/k8s.io/component-base/metrics/sampling-histogram.go
@@ -19,7 +19,7 @@ package metrics
 import (
 	"github.com/blang/semver"
 
-	promext "k8s.io/component-base/metrics/prometheus_extension"
+	promext "k8s.io/component-base/metrics/prometheusextension"
 )
 
 // SamplingHistogram is our internal representation for our wrapping struct around prometheus
diff --git a/vendor/modules.txt b/vendor/modules.txt
index ed4527e0fc99..1bfdf41d2441 100644
--- a/vendor/modules.txt
+++ b/vendor/modules.txt
@@ -2171,7 +2171,7 @@ k8s.io/component-base/metrics/prometheus/ratelimiter
 k8s.io/component-base/metrics/prometheus/restclient
 k8s.io/component-base/metrics/prometheus/version
 k8s.io/component-base/metrics/prometheus/workqueue
-k8s.io/component-base/metrics/prometheus_extension
+k8s.io/component-base/metrics/prometheusextension
 k8s.io/component-base/metrics/testutil
 k8s.io/component-base/term
 k8s.io/component-base/version

From 64943ed47eef5430bd14f9d70bf3401a5cd43fac Mon Sep 17 00:00:00 2001
From: Mike Spreitzer <mspreitz@us.ibm.com>
Date: Fri, 11 Sep 2020 03:56:29 -0400
Subject: [PATCH 5/7] fix wrapper

---
 .../src/k8s.io/component-base/metrics/sampling-histogram.go    | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/staging/src/k8s.io/component-base/metrics/sampling-histogram.go b/staging/src/k8s.io/component-base/metrics/sampling-histogram.go
index 1492838a4460..e699eec61cb6 100644
--- a/staging/src/k8s.io/component-base/metrics/sampling-histogram.go
+++ b/staging/src/k8s.io/component-base/metrics/sampling-histogram.go
@@ -64,7 +64,8 @@ func (h *SamplingHistogram) DeprecatedVersion() *semver.Version {
 func (h *SamplingHistogram) initializeMetric() {
 	h.SamplingHistogramOpts.annotateStabilityLevel()
 	// this actually creates the underlying prometheus gauge.
-	h.setPrometheusSamplingHistogram(promext.NewSamplingHistogram(h.SamplingHistogramOpts.toPromSamplingHistogramOpts()))
+	sh, _ := promext.NewSamplingHistogram(h.SamplingHistogramOpts.toPromSamplingHistogramOpts())
+	h.setPrometheusSamplingHistogram(sh)
 }
 
 // initializeDeprecatedMetric invokes the actual prometheus.SamplingHistogram object instantiation

From 0e0bcd9c4f3fa1c7166f65cb1f084cfa6a9d1185 Mon Sep 17 00:00:00 2001
From: Mike Spreitzer <mspreitz@us.ibm.com>
Date: Fri, 11 Sep 2020 22:03:55 -0400
Subject: [PATCH 6/7] Add hack to get k8s.io/utils/clock/testing in vendor/

As per https://github.com/kubernetes/kubernetes/pull/84205/#issuecomment-660362689
---
 build/tools.go                                |   1 +
 vendor/k8s.io/utils/clock/BUILD               |   5 +-
 vendor/k8s.io/utils/clock/testing/BUILD       |  24 ++
 .../k8s.io/utils/clock/testing/fake_clock.go  | 274 ++++++++++++++++++
 vendor/modules.txt                            |   1 +
 5 files changed, 304 insertions(+), 1 deletion(-)
 create mode 100644 vendor/k8s.io/utils/clock/testing/BUILD
 create mode 100644 vendor/k8s.io/utils/clock/testing/fake_clock.go

diff --git a/build/tools.go b/build/tools.go
index 33958d7bfba6..71799c1d04e1 100644
--- a/build/tools.go
+++ b/build/tools.go
@@ -29,4 +29,5 @@ import (
 	_ "k8s.io/gengo/examples/import-boss/generators"
 	_ "k8s.io/gengo/examples/set-gen/generators"
 	_ "k8s.io/kube-openapi/cmd/openapi-gen"
+	_ "k8s.io/utils/clock/testing"
 )
diff --git a/vendor/k8s.io/utils/clock/BUILD b/vendor/k8s.io/utils/clock/BUILD
index 1b2e304c37f3..aa2c1799dc19 100644
--- a/vendor/k8s.io/utils/clock/BUILD
+++ b/vendor/k8s.io/utils/clock/BUILD
@@ -17,7 +17,10 @@ filegroup(
 
 filegroup(
     name = "all-srcs",
-    srcs = [":package-srcs"],
+    srcs = [
+        ":package-srcs",
+        "//vendor/k8s.io/utils/clock/testing:all-srcs",
+    ],
     tags = ["automanaged"],
     visibility = ["//visibility:public"],
 )
diff --git a/vendor/k8s.io/utils/clock/testing/BUILD b/vendor/k8s.io/utils/clock/testing/BUILD
new file mode 100644
index 000000000000..6a254d8010ed
--- /dev/null
+++ b/vendor/k8s.io/utils/clock/testing/BUILD
@@ -0,0 +1,24 @@
+load("@io_bazel_rules_go//go:def.bzl", "go_library")
+
+go_library(
+    name = "go_default_library",
+    srcs = ["fake_clock.go"],
+    importmap = "k8s.io/kubernetes/vendor/k8s.io/utils/clock/testing",
+    importpath = "k8s.io/utils/clock/testing",
+    visibility = ["//visibility:public"],
+    deps = ["//vendor/k8s.io/utils/clock:go_default_library"],
+)
+
+filegroup(
+    name = "package-srcs",
+    srcs = glob(["**"]),
+    tags = ["automanaged"],
+    visibility = ["//visibility:private"],
+)
+
+filegroup(
+    name = "all-srcs",
+    srcs = [":package-srcs"],
+    tags = ["automanaged"],
+    visibility = ["//visibility:public"],
+)
diff --git a/vendor/k8s.io/utils/clock/testing/fake_clock.go b/vendor/k8s.io/utils/clock/testing/fake_clock.go
new file mode 100644
index 000000000000..2fc34aed6db5
--- /dev/null
+++ b/vendor/k8s.io/utils/clock/testing/fake_clock.go
@@ -0,0 +1,274 @@
+/*
+Copyright 2014 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 testing
+
+import (
+	"sync"
+	"time"
+
+	"k8s.io/utils/clock"
+)
+
+var (
+	_ = clock.Clock(&FakeClock{})
+	_ = clock.Clock(&IntervalClock{})
+)
+
+// FakeClock implements clock.Clock, but returns an arbitrary time.
+type FakeClock struct {
+	lock sync.RWMutex
+	time time.Time
+
+	// waiters are waiting for the fake time to pass their specified time
+	waiters []*fakeClockWaiter
+}
+
+type fakeClockWaiter struct {
+	targetTime    time.Time
+	stepInterval  time.Duration
+	skipIfBlocked bool
+	destChan      chan time.Time
+	fired         bool
+}
+
+// NewFakeClock constructs a fake clock set to the provided time.
+func NewFakeClock(t time.Time) *FakeClock {
+	return &FakeClock{
+		time: t,
+	}
+}
+
+// Now returns f's time.
+func (f *FakeClock) Now() time.Time {
+	f.lock.RLock()
+	defer f.lock.RUnlock()
+	return f.time
+}
+
+// Since returns time since the time in f.
+func (f *FakeClock) Since(ts time.Time) time.Duration {
+	f.lock.RLock()
+	defer f.lock.RUnlock()
+	return f.time.Sub(ts)
+}
+
+// After is the fake version of time.After(d).
+func (f *FakeClock) After(d time.Duration) <-chan time.Time {
+	f.lock.Lock()
+	defer f.lock.Unlock()
+	stopTime := f.time.Add(d)
+	ch := make(chan time.Time, 1) // Don't block!
+	f.waiters = append(f.waiters, &fakeClockWaiter{
+		targetTime: stopTime,
+		destChan:   ch,
+	})
+	return ch
+}
+
+// NewTimer constructs a fake timer, akin to time.NewTimer(d).
+func (f *FakeClock) NewTimer(d time.Duration) clock.Timer {
+	f.lock.Lock()
+	defer f.lock.Unlock()
+	stopTime := f.time.Add(d)
+	ch := make(chan time.Time, 1) // Don't block!
+	timer := &fakeTimer{
+		fakeClock: f,
+		waiter: fakeClockWaiter{
+			targetTime: stopTime,
+			destChan:   ch,
+		},
+	}
+	f.waiters = append(f.waiters, &timer.waiter)
+	return timer
+}
+
+// Tick constructs a fake ticker, akin to time.Tick
+func (f *FakeClock) Tick(d time.Duration) <-chan time.Time {
+	if d <= 0 {
+		return nil
+	}
+	f.lock.Lock()
+	defer f.lock.Unlock()
+	tickTime := f.time.Add(d)
+	ch := make(chan time.Time, 1) // hold one tick
+	f.waiters = append(f.waiters, &fakeClockWaiter{
+		targetTime:    tickTime,
+		stepInterval:  d,
+		skipIfBlocked: true,
+		destChan:      ch,
+	})
+
+	return ch
+}
+
+// Step moves the clock by Duration and notifies anyone that's called After,
+// Tick, or NewTimer.
+func (f *FakeClock) Step(d time.Duration) {
+	f.lock.Lock()
+	defer f.lock.Unlock()
+	f.setTimeLocked(f.time.Add(d))
+}
+
+// SetTime sets the time.
+func (f *FakeClock) SetTime(t time.Time) {
+	f.lock.Lock()
+	defer f.lock.Unlock()
+	f.setTimeLocked(t)
+}
+
+// Actually changes the time and checks any waiters. f must be write-locked.
+func (f *FakeClock) setTimeLocked(t time.Time) {
+	f.time = t
+	newWaiters := make([]*fakeClockWaiter, 0, len(f.waiters))
+	for i := range f.waiters {
+		w := f.waiters[i]
+		if !w.targetTime.After(t) {
+
+			if w.skipIfBlocked {
+				select {
+				case w.destChan <- t:
+					w.fired = true
+				default:
+				}
+			} else {
+				w.destChan <- t
+				w.fired = true
+			}
+
+			if w.stepInterval > 0 {
+				for !w.targetTime.After(t) {
+					w.targetTime = w.targetTime.Add(w.stepInterval)
+				}
+				newWaiters = append(newWaiters, w)
+			}
+
+		} else {
+			newWaiters = append(newWaiters, f.waiters[i])
+		}
+	}
+	f.waiters = newWaiters
+}
+
+// HasWaiters returns true if After has been called on f but not yet satisfied (so you can
+// write race-free tests).
+func (f *FakeClock) HasWaiters() bool {
+	f.lock.RLock()
+	defer f.lock.RUnlock()
+	return len(f.waiters) > 0
+}
+
+// Sleep is akin to time.Sleep
+func (f *FakeClock) Sleep(d time.Duration) {
+	f.Step(d)
+}
+
+// IntervalClock implements clock.Clock, but each invocation of Now steps the clock forward the specified duration
+type IntervalClock struct {
+	Time     time.Time
+	Duration time.Duration
+}
+
+// Now returns i's time.
+func (i *IntervalClock) Now() time.Time {
+	i.Time = i.Time.Add(i.Duration)
+	return i.Time
+}
+
+// Since returns time since the time in i.
+func (i *IntervalClock) Since(ts time.Time) time.Duration {
+	return i.Time.Sub(ts)
+}
+
+// After is unimplemented, will panic.
+// TODO: make interval clock use FakeClock so this can be implemented.
+func (*IntervalClock) After(d time.Duration) <-chan time.Time {
+	panic("IntervalClock doesn't implement After")
+}
+
+// NewTimer is unimplemented, will panic.
+// TODO: make interval clock use FakeClock so this can be implemented.
+func (*IntervalClock) NewTimer(d time.Duration) clock.Timer {
+	panic("IntervalClock doesn't implement NewTimer")
+}
+
+// Tick is unimplemented, will panic.
+// TODO: make interval clock use FakeClock so this can be implemented.
+func (*IntervalClock) Tick(d time.Duration) <-chan time.Time {
+	panic("IntervalClock doesn't implement Tick")
+}
+
+// Sleep is unimplemented, will panic.
+func (*IntervalClock) Sleep(d time.Duration) {
+	panic("IntervalClock doesn't implement Sleep")
+}
+
+var _ = clock.Timer(&fakeTimer{})
+
+// fakeTimer implements clock.Timer based on a FakeClock.
+type fakeTimer struct {
+	fakeClock *FakeClock
+	waiter    fakeClockWaiter
+}
+
+// C returns the channel that notifies when this timer has fired.
+func (f *fakeTimer) C() <-chan time.Time {
+	return f.waiter.destChan
+}
+
+// Stop stops the timer and returns true if the timer has not yet fired, or false otherwise.
+func (f *fakeTimer) Stop() bool {
+	f.fakeClock.lock.Lock()
+	defer f.fakeClock.lock.Unlock()
+
+	newWaiters := make([]*fakeClockWaiter, 0, len(f.fakeClock.waiters))
+	for i := range f.fakeClock.waiters {
+		w := f.fakeClock.waiters[i]
+		if w != &f.waiter {
+			newWaiters = append(newWaiters, w)
+		}
+	}
+
+	f.fakeClock.waiters = newWaiters
+
+	return !f.waiter.fired
+}
+
+// Reset resets the timer to the fake clock's "now" + d. It returns true if the timer has not yet
+// fired, or false otherwise.
+func (f *fakeTimer) Reset(d time.Duration) bool {
+	f.fakeClock.lock.Lock()
+	defer f.fakeClock.lock.Unlock()
+
+	active := !f.waiter.fired
+
+	f.waiter.fired = false
+	f.waiter.targetTime = f.fakeClock.time.Add(d)
+
+	var isWaiting bool
+	for i := range f.fakeClock.waiters {
+		w := f.fakeClock.waiters[i]
+		if w == &f.waiter {
+			isWaiting = true
+			break
+		}
+	}
+	if !isWaiting {
+		f.fakeClock.waiters = append(f.fakeClock.waiters, &f.waiter)
+	}
+
+	return active
+}
diff --git a/vendor/modules.txt b/vendor/modules.txt
index 1bfdf41d2441..22c2f47f3416 100644
--- a/vendor/modules.txt
+++ b/vendor/modules.txt
@@ -2465,6 +2465,7 @@ k8s.io/system-validators/validators
 # k8s.io/utils => k8s.io/utils v0.0.0-20200729134348-d5654de09c73
 k8s.io/utils/buffer
 k8s.io/utils/clock
+k8s.io/utils/clock/testing
 k8s.io/utils/exec
 k8s.io/utils/exec/testing
 k8s.io/utils/inotify

From bbb0cf5d31116cb383079e24dbd05c1a110c67e3 Mon Sep 17 00:00:00 2001
From: Mike Spreitzer <mspreitz@us.ibm.com>
Date: Fri, 11 Sep 2020 23:16:39 -0400
Subject: [PATCH 7/7] Add control flow to silence static checker

Before this change, the staticcheck test in the pull-kubernetes-verify
job complained about some possible nil pointer dereferences, but those
would never happen because `t.Errorf` aborts the test.  Added control
flow (that will never be reached, if you understand `t.Errorf`) to
make it obvious that the nil dereferences will never happen.
---
 .../metrics/prometheusextension/sampling-histogram_test.go  | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/staging/src/k8s.io/component-base/metrics/prometheusextension/sampling-histogram_test.go b/staging/src/k8s.io/component-base/metrics/prometheusextension/sampling-histogram_test.go
index c27765f0b15a..01aacada968e 100644
--- a/staging/src/k8s.io/component-base/metrics/prometheusextension/sampling-histogram_test.go
+++ b/staging/src/k8s.io/component-base/metrics/prometheusextension/sampling-histogram_test.go
@@ -93,6 +93,7 @@ func expectHistogram(t *testing.T, when string, sh SamplingHistogram, buckets ..
 	}
 	if dtom.Histogram == nil {
 		t.Errorf("%s, Collect returned a Metric without a Histogram: %#+v", when, dtom)
+		return
 	}
 	mh := dtom.Histogram
 	if len(mh.Bucket) != len(buckets)-1 {
@@ -100,16 +101,17 @@ func expectHistogram(t *testing.T, when string, sh SamplingHistogram, buckets ..
 	}
 	if mh.SampleCount == nil {
 		t.Errorf("%s, got Histogram with nil SampleCount", when)
-	}
-	if *(mh.SampleCount) != buckets[len(mh.Bucket)] {
+	} else if *(mh.SampleCount) != buckets[len(mh.Bucket)] {
 		t.Errorf("%s, SampleCount=%d but expected %d", when, *(mh.SampleCount), buckets[len(mh.Bucket)])
 	}
 	for i, mhBucket := range mh.Bucket {
 		if mhBucket == nil {
 			t.Errorf("%s, bucket %d was nil", when, i)
+			continue
 		}
 		if mhBucket.UpperBound == nil || mhBucket.CumulativeCount == nil {
 			t.Errorf("%s, bucket %d had nil bound or count", when, i)
+			continue
 		}
 		ub := float64(i)
 		if ub != *(mhBucket.UpperBound) {