build: move e2e dependencies into e2e/go.mod

Several packages are only used while running the e2e suite. These
packages are less important to update, as the they can not influence the
final executable that is part of the Ceph-CSI container-image.

By moving these dependencies out of the main Ceph-CSI go.mod, it is
easier to identify if a reported CVE affects Ceph-CSI, or only the
testing (like most of the Kubernetes CVEs).

Signed-off-by: Niels de Vos <ndevos@ibm.com>

e2e/vendor/golang.org/x/net/trace/events.go

@@ -0,0 +1,532 @@
+// Copyright 2015 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package trace
+
+import (
+	"bytes"
+	"fmt"
+	"html/template"
+	"io"
+	"log"
+	"net/http"
+	"runtime"
+	"sort"
+	"strconv"
+	"strings"
+	"sync"
+	"sync/atomic"
+	"text/tabwriter"
+	"time"
+)
+
+const maxEventsPerLog = 100
+
+type bucket struct {
+	MaxErrAge time.Duration
+	String    string
+}
+
+var buckets = []bucket{
+	{0, "total"},
+	{10 * time.Second, "errs<10s"},
+	{1 * time.Minute, "errs<1m"},
+	{10 * time.Minute, "errs<10m"},
+	{1 * time.Hour, "errs<1h"},
+	{10 * time.Hour, "errs<10h"},
+	{24000 * time.Hour, "errors"},
+}
+
+// RenderEvents renders the HTML page typically served at /debug/events.
+// It does not do any auth checking. The request may be nil.
+//
+// Most users will use the Events handler.
+func RenderEvents(w http.ResponseWriter, req *http.Request, sensitive bool) {
+	now := time.Now()
+	data := &struct {
+		Families []string // family names
+		Buckets  []bucket
+		Counts   [][]int // eventLog count per family/bucket
+
+		// Set when a bucket has been selected.
+		Family    string
+		Bucket    int
+		EventLogs eventLogs
+		Expanded  bool
+	}{
+		Buckets: buckets,
+	}
+
+	data.Families = make([]string, 0, len(families))
+	famMu.RLock()
+	for name := range families {
+		data.Families = append(data.Families, name)
+	}
+	famMu.RUnlock()
+	sort.Strings(data.Families)
+
+	// Count the number of eventLogs in each family for each error age.
+	data.Counts = make([][]int, len(data.Families))
+	for i, name := range data.Families {
+		// TODO(sameer): move this loop under the family lock.
+		f := getEventFamily(name)
+		data.Counts[i] = make([]int, len(data.Buckets))
+		for j, b := range data.Buckets {
+			data.Counts[i][j] = f.Count(now, b.MaxErrAge)
+		}
+	}
+
+	if req != nil {
+		var ok bool
+		data.Family, data.Bucket, ok = parseEventsArgs(req)
+		if !ok {
+			// No-op
+		} else {
+			data.EventLogs = getEventFamily(data.Family).Copy(now, buckets[data.Bucket].MaxErrAge)
+		}
+		if data.EventLogs != nil {
+			defer data.EventLogs.Free()
+			sort.Sort(data.EventLogs)
+		}
+		if exp, err := strconv.ParseBool(req.FormValue("exp")); err == nil {
+			data.Expanded = exp
+		}
+	}
+
+	famMu.RLock()
+	defer famMu.RUnlock()
+	if err := eventsTmpl().Execute(w, data); err != nil {
+		log.Printf("net/trace: Failed executing template: %v", err)
+	}
+}
+
+func parseEventsArgs(req *http.Request) (fam string, b int, ok bool) {
+	fam, bStr := req.FormValue("fam"), req.FormValue("b")
+	if fam == "" || bStr == "" {
+		return "", 0, false
+	}
+	b, err := strconv.Atoi(bStr)
+	if err != nil || b < 0 || b >= len(buckets) {
+		return "", 0, false
+	}
+	return fam, b, true
+}
+
+// An EventLog provides a log of events associated with a specific object.
+type EventLog interface {
+	// Printf formats its arguments with fmt.Sprintf and adds the
+	// result to the event log.
+	Printf(format string, a ...interface{})
+
+	// Errorf is like Printf, but it marks this event as an error.
+	Errorf(format string, a ...interface{})
+
+	// Finish declares that this event log is complete.
+	// The event log should not be used after calling this method.
+	Finish()
+}
+
+// NewEventLog returns a new EventLog with the specified family name
+// and title.
+func NewEventLog(family, title string) EventLog {
+	el := newEventLog()
+	el.ref()
+	el.Family, el.Title = family, title
+	el.Start = time.Now()
+	el.events = make([]logEntry, 0, maxEventsPerLog)
+	el.stack = make([]uintptr, 32)
+	n := runtime.Callers(2, el.stack)
+	el.stack = el.stack[:n]
+
+	getEventFamily(family).add(el)
+	return el
+}
+
+func (el *eventLog) Finish() {
+	getEventFamily(el.Family).remove(el)
+	el.unref() // matches ref in New
+}
+
+var (
+	famMu    sync.RWMutex
+	families = make(map[string]*eventFamily) // family name => family
+)
+
+func getEventFamily(fam string) *eventFamily {
+	famMu.Lock()
+	defer famMu.Unlock()
+	f := families[fam]
+	if f == nil {
+		f = &eventFamily{}
+		families[fam] = f
+	}
+	return f
+}
+
+type eventFamily struct {
+	mu        sync.RWMutex
+	eventLogs eventLogs
+}
+
+func (f *eventFamily) add(el *eventLog) {
+	f.mu.Lock()
+	f.eventLogs = append(f.eventLogs, el)
+	f.mu.Unlock()
+}
+
+func (f *eventFamily) remove(el *eventLog) {
+	f.mu.Lock()
+	defer f.mu.Unlock()
+	for i, el0 := range f.eventLogs {
+		if el == el0 {
+			copy(f.eventLogs[i:], f.eventLogs[i+1:])
+			f.eventLogs = f.eventLogs[:len(f.eventLogs)-1]
+			return
+		}
+	}
+}
+
+func (f *eventFamily) Count(now time.Time, maxErrAge time.Duration) (n int) {
+	f.mu.RLock()
+	defer f.mu.RUnlock()
+	for _, el := range f.eventLogs {
+		if el.hasRecentError(now, maxErrAge) {
+			n++
+		}
+	}
+	return
+}
+
+func (f *eventFamily) Copy(now time.Time, maxErrAge time.Duration) (els eventLogs) {
+	f.mu.RLock()
+	defer f.mu.RUnlock()
+	els = make(eventLogs, 0, len(f.eventLogs))
+	for _, el := range f.eventLogs {
+		if el.hasRecentError(now, maxErrAge) {
+			el.ref()
+			els = append(els, el)
+		}
+	}
+	return
+}
+
+type eventLogs []*eventLog
+
+// Free calls unref on each element of the list.
+func (els eventLogs) Free() {
+	for _, el := range els {
+		el.unref()
+	}
+}
+
+// eventLogs may be sorted in reverse chronological order.
+func (els eventLogs) Len() int           { return len(els) }
+func (els eventLogs) Less(i, j int) bool { return els[i].Start.After(els[j].Start) }
+func (els eventLogs) Swap(i, j int)      { els[i], els[j] = els[j], els[i] }
+
+// A logEntry is a timestamped log entry in an event log.
+type logEntry struct {
+	When    time.Time
+	Elapsed time.Duration // since previous event in log
+	NewDay  bool          // whether this event is on a different day to the previous event
+	What    string
+	IsErr   bool
+}
+
+// WhenString returns a string representation of the elapsed time of the event.
+// It will include the date if midnight was crossed.
+func (e logEntry) WhenString() string {
+	if e.NewDay {
+		return e.When.Format("2006/01/02 15:04:05.000000")
+	}
+	return e.When.Format("15:04:05.000000")
+}
+
+// An eventLog represents an active event log.
+type eventLog struct {
+	// Family is the top-level grouping of event logs to which this belongs.
+	Family string
+
+	// Title is the title of this event log.
+	Title string
+
+	// Timing information.
+	Start time.Time
+
+	// Call stack where this event log was created.
+	stack []uintptr
+
+	// Append-only sequence of events.
+	//
+	// TODO(sameer): change this to a ring buffer to avoid the array copy
+	// when we hit maxEventsPerLog.
+	mu            sync.RWMutex
+	events        []logEntry
+	LastErrorTime time.Time
+	discarded     int
+
+	refs int32 // how many buckets this is in
+}
+
+func (el *eventLog) reset() {
+	// Clear all but the mutex. Mutexes may not be copied, even when unlocked.
+	el.Family = ""
+	el.Title = ""
+	el.Start = time.Time{}
+	el.stack = nil
+	el.events = nil
+	el.LastErrorTime = time.Time{}
+	el.discarded = 0
+	el.refs = 0
+}
+
+func (el *eventLog) hasRecentError(now time.Time, maxErrAge time.Duration) bool {
+	if maxErrAge == 0 {
+		return true
+	}
+	el.mu.RLock()
+	defer el.mu.RUnlock()
+	return now.Sub(el.LastErrorTime) < maxErrAge
+}
+
+// delta returns the elapsed time since the last event or the log start,
+// and whether it spans midnight.
+// L >= el.mu
+func (el *eventLog) delta(t time.Time) (time.Duration, bool) {
+	if len(el.events) == 0 {
+		return t.Sub(el.Start), false
+	}
+	prev := el.events[len(el.events)-1].When
+	return t.Sub(prev), prev.Day() != t.Day()
+
+}
+
+func (el *eventLog) Printf(format string, a ...interface{}) {
+	el.printf(false, format, a...)
+}
+
+func (el *eventLog) Errorf(format string, a ...interface{}) {
+	el.printf(true, format, a...)
+}
+
+func (el *eventLog) printf(isErr bool, format string, a ...interface{}) {
+	e := logEntry{When: time.Now(), IsErr: isErr, What: fmt.Sprintf(format, a...)}
+	el.mu.Lock()
+	e.Elapsed, e.NewDay = el.delta(e.When)
+	if len(el.events) < maxEventsPerLog {
+		el.events = append(el.events, e)
+	} else {
+		// Discard the oldest event.
+		if el.discarded == 0 {
+			// el.discarded starts at two to count for the event it
+			// is replacing, plus the next one that we are about to
+			// drop.
+			el.discarded = 2
+		} else {
+			el.discarded++
+		}
+		// TODO(sameer): if this causes allocations on a critical path,
+		// change eventLog.What to be a fmt.Stringer, as in trace.go.
+		el.events[0].What = fmt.Sprintf("(%d events discarded)", el.discarded)
+		// The timestamp of the discarded meta-event should be
+		// the time of the last event it is representing.
+		el.events[0].When = el.events[1].When
+		copy(el.events[1:], el.events[2:])
+		el.events[maxEventsPerLog-1] = e
+	}
+	if e.IsErr {
+		el.LastErrorTime = e.When
+	}
+	el.mu.Unlock()
+}
+
+func (el *eventLog) ref() {
+	atomic.AddInt32(&el.refs, 1)
+}
+
+func (el *eventLog) unref() {
+	if atomic.AddInt32(&el.refs, -1) == 0 {
+		freeEventLog(el)
+	}
+}
+
+func (el *eventLog) When() string {
+	return el.Start.Format("2006/01/02 15:04:05.000000")
+}
+
+func (el *eventLog) ElapsedTime() string {
+	elapsed := time.Since(el.Start)
+	return fmt.Sprintf("%.6f", elapsed.Seconds())
+}
+
+func (el *eventLog) Stack() string {
+	buf := new(bytes.Buffer)
+	tw := tabwriter.NewWriter(buf, 1, 8, 1, '\t', 0)
+	printStackRecord(tw, el.stack)
+	tw.Flush()
+	return buf.String()
+}
+
+// printStackRecord prints the function + source line information
+// for a single stack trace.
+// Adapted from runtime/pprof/pprof.go.
+func printStackRecord(w io.Writer, stk []uintptr) {
+	for _, pc := range stk {
+		f := runtime.FuncForPC(pc)
+		if f == nil {
+			continue
+		}
+		file, line := f.FileLine(pc)
+		name := f.Name()
+		// Hide runtime.goexit and any runtime functions at the beginning.
+		if strings.HasPrefix(name, "runtime.") {
+			continue
+		}
+		fmt.Fprintf(w, "#   %s\t%s:%d\n", name, file, line)
+	}
+}
+
+func (el *eventLog) Events() []logEntry {
+	el.mu.RLock()
+	defer el.mu.RUnlock()
+	return el.events
+}
+
+// freeEventLogs is a freelist of *eventLog
+var freeEventLogs = make(chan *eventLog, 1000)
+
+// newEventLog returns a event log ready to use.
+func newEventLog() *eventLog {
+	select {
+	case el := <-freeEventLogs:
+		return el
+	default:
+		return new(eventLog)
+	}
+}
+
+// freeEventLog adds el to freeEventLogs if there's room.
+// This is non-blocking.
+func freeEventLog(el *eventLog) {
+	el.reset()
+	select {
+	case freeEventLogs <- el:
+	default:
+	}
+}
+
+var eventsTmplCache *template.Template
+var eventsTmplOnce sync.Once
+
+func eventsTmpl() *template.Template {
+	eventsTmplOnce.Do(func() {
+		eventsTmplCache = template.Must(template.New("events").Funcs(template.FuncMap{
+			"elapsed":   elapsed,
+			"trimSpace": strings.TrimSpace,
+		}).Parse(eventsHTML))
+	})
+	return eventsTmplCache
+}
+
+const eventsHTML = `
+<html>
+	<head>
+		<title>events</title>
+	</head>
+	<style type="text/css">
+		body {
+			font-family: sans-serif;
+		}
+		table#req-status td.family {
+			padding-right: 2em;
+		}
+		table#req-status td.active {
+			padding-right: 1em;
+		}
+		table#req-status td.empty {
+			color: #aaa;
+		}
+		table#reqs {
+			margin-top: 1em;
+		}
+		table#reqs tr.first {
+			{{if $.Expanded}}font-weight: bold;{{end}}
+		}
+		table#reqs td {
+			font-family: monospace;
+		}
+		table#reqs td.when {
+			text-align: right;
+			white-space: nowrap;
+		}
+		table#reqs td.elapsed {
+			padding: 0 0.5em;
+			text-align: right;
+			white-space: pre;
+			width: 10em;
+		}
+		address {
+			font-size: smaller;
+			margin-top: 5em;
+		}
+	</style>
+	<body>
+
+<h1>/debug/events</h1>
+
+<table id="req-status">
+	{{range $i, $fam := .Families}}
+	<tr>
+		<td class="family">{{$fam}}</td>
+
+	        {{range $j, $bucket := $.Buckets}}
+	        {{$n := index $.Counts $i $j}}
+		<td class="{{if not $bucket.MaxErrAge}}active{{end}}{{if not $n}}empty{{end}}">
+	                {{if $n}}<a href="?fam={{$fam}}&b={{$j}}{{if $.Expanded}}&exp=1{{end}}">{{end}}
+		        [{{$n}} {{$bucket.String}}]
+			{{if $n}}</a>{{end}}
+		</td>
+                {{end}}
+
+	</tr>{{end}}
+</table>
+
+{{if $.EventLogs}}
+<hr />
+<h3>Family: {{$.Family}}</h3>
+
+{{if $.Expanded}}<a href="?fam={{$.Family}}&b={{$.Bucket}}">{{end}}
+[Summary]{{if $.Expanded}}</a>{{end}}
+
+{{if not $.Expanded}}<a href="?fam={{$.Family}}&b={{$.Bucket}}&exp=1">{{end}}
+[Expanded]{{if not $.Expanded}}</a>{{end}}
+
+<table id="reqs">
+	<tr><th>When</th><th>Elapsed</th></tr>
+	{{range $el := $.EventLogs}}
+	<tr class="first">
+		<td class="when">{{$el.When}}</td>
+		<td class="elapsed">{{$el.ElapsedTime}}</td>
+		<td>{{$el.Title}}
+	</tr>
+	{{if $.Expanded}}
+	<tr>
+		<td class="when"></td>
+		<td class="elapsed"></td>
+		<td><pre>{{$el.Stack|trimSpace}}</pre></td>
+	</tr>
+	{{range $el.Events}}
+	<tr>
+		<td class="when">{{.WhenString}}</td>
+		<td class="elapsed">{{elapsed .Elapsed}}</td>
+		<td>.{{if .IsErr}}E{{else}}.{{end}}. {{.What}}</td>
+	</tr>
+	{{end}}
+	{{end}}
+	{{end}}
+</table>
+{{end}}
+	</body>
+</html>
+`

e2e/vendor/golang.org/x/net/trace/histogram.go

@@ -0,0 +1,365 @@
+// Copyright 2015 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package trace
+
+// This file implements histogramming for RPC statistics collection.
+
+import (
+	"bytes"
+	"fmt"
+	"html/template"
+	"log"
+	"math"
+	"sync"
+
+	"golang.org/x/net/internal/timeseries"
+)
+
+const (
+	bucketCount = 38
+)
+
+// histogram keeps counts of values in buckets that are spaced
+// out in powers of 2: 0-1, 2-3, 4-7...
+// histogram implements timeseries.Observable
+type histogram struct {
+	sum          int64   // running total of measurements
+	sumOfSquares float64 // square of running total
+	buckets      []int64 // bucketed values for histogram
+	value        int     // holds a single value as an optimization
+	valueCount   int64   // number of values recorded for single value
+}
+
+// addMeasurement records a value measurement observation to the histogram.
+func (h *histogram) addMeasurement(value int64) {
+	// TODO: assert invariant
+	h.sum += value
+	h.sumOfSquares += float64(value) * float64(value)
+
+	bucketIndex := getBucket(value)
+
+	if h.valueCount == 0 || (h.valueCount > 0 && h.value == bucketIndex) {
+		h.value = bucketIndex
+		h.valueCount++
+	} else {
+		h.allocateBuckets()
+		h.buckets[bucketIndex]++
+	}
+}
+
+func (h *histogram) allocateBuckets() {
+	if h.buckets == nil {
+		h.buckets = make([]int64, bucketCount)
+		h.buckets[h.value] = h.valueCount
+		h.value = 0
+		h.valueCount = -1
+	}
+}
+
+func log2(i int64) int {
+	n := 0
+	for ; i >= 0x100; i >>= 8 {
+		n += 8
+	}
+	for ; i > 0; i >>= 1 {
+		n += 1
+	}
+	return n
+}
+
+func getBucket(i int64) (index int) {
+	index = log2(i) - 1
+	if index < 0 {
+		index = 0
+	}
+	if index >= bucketCount {
+		index = bucketCount - 1
+	}
+	return
+}
+
+// Total returns the number of recorded observations.
+func (h *histogram) total() (total int64) {
+	if h.valueCount >= 0 {
+		total = h.valueCount
+	}
+	for _, val := range h.buckets {
+		total += int64(val)
+	}
+	return
+}
+
+// Average returns the average value of recorded observations.
+func (h *histogram) average() float64 {
+	t := h.total()
+	if t == 0 {
+		return 0
+	}
+	return float64(h.sum) / float64(t)
+}
+
+// Variance returns the variance of recorded observations.
+func (h *histogram) variance() float64 {
+	t := float64(h.total())
+	if t == 0 {
+		return 0
+	}
+	s := float64(h.sum) / t
+	return h.sumOfSquares/t - s*s
+}
+
+// StandardDeviation returns the standard deviation of recorded observations.
+func (h *histogram) standardDeviation() float64 {
+	return math.Sqrt(h.variance())
+}
+
+// PercentileBoundary estimates the value that the given fraction of recorded
+// observations are less than.
+func (h *histogram) percentileBoundary(percentile float64) int64 {
+	total := h.total()
+
+	// Corner cases (make sure result is strictly less than Total())
+	if total == 0 {
+		return 0
+	} else if total == 1 {
+		return int64(h.average())
+	}
+
+	percentOfTotal := round(float64(total) * percentile)
+	var runningTotal int64
+
+	for i := range h.buckets {
+		value := h.buckets[i]
+		runningTotal += value
+		if runningTotal == percentOfTotal {
+			// We hit an exact bucket boundary. If the next bucket has data, it is a
+			// good estimate of the value. If the bucket is empty, we interpolate the
+			// midpoint between the next bucket's boundary and the next non-zero
+			// bucket. If the remaining buckets are all empty, then we use the
+			// boundary for the next bucket as the estimate.
+			j := uint8(i + 1)
+			min := bucketBoundary(j)
+			if runningTotal < total {
+				for h.buckets[j] == 0 {
+					j++
+				}
+			}
+			max := bucketBoundary(j)
+			return min + round(float64(max-min)/2)
+		} else if runningTotal > percentOfTotal {
+			// The value is in this bucket. Interpolate the value.
+			delta := runningTotal - percentOfTotal
+			percentBucket := float64(value-delta) / float64(value)
+			bucketMin := bucketBoundary(uint8(i))
+			nextBucketMin := bucketBoundary(uint8(i + 1))
+			bucketSize := nextBucketMin - bucketMin
+			return bucketMin + round(percentBucket*float64(bucketSize))
+		}
+	}
+	return bucketBoundary(bucketCount - 1)
+}
+
+// Median returns the estimated median of the observed values.
+func (h *histogram) median() int64 {
+	return h.percentileBoundary(0.5)
+}
+
+// Add adds other to h.
+func (h *histogram) Add(other timeseries.Observable) {
+	o := other.(*histogram)
+	if o.valueCount == 0 {
+		// Other histogram is empty
+	} else if h.valueCount >= 0 && o.valueCount > 0 && h.value == o.value {
+		// Both have a single bucketed value, aggregate them
+		h.valueCount += o.valueCount
+	} else {
+		// Two different values necessitate buckets in this histogram
+		h.allocateBuckets()
+		if o.valueCount >= 0 {
+			h.buckets[o.value] += o.valueCount
+		} else {
+			for i := range h.buckets {
+				h.buckets[i] += o.buckets[i]
+			}
+		}
+	}
+	h.sumOfSquares += o.sumOfSquares
+	h.sum += o.sum
+}
+
+// Clear resets the histogram to an empty state, removing all observed values.
+func (h *histogram) Clear() {
+	h.buckets = nil
+	h.value = 0
+	h.valueCount = 0
+	h.sum = 0
+	h.sumOfSquares = 0
+}
+
+// CopyFrom copies from other, which must be a *histogram, into h.
+func (h *histogram) CopyFrom(other timeseries.Observable) {
+	o := other.(*histogram)
+	if o.valueCount == -1 {
+		h.allocateBuckets()
+		copy(h.buckets, o.buckets)
+	}
+	h.sum = o.sum
+	h.sumOfSquares = o.sumOfSquares
+	h.value = o.value
+	h.valueCount = o.valueCount
+}
+
+// Multiply scales the histogram by the specified ratio.
+func (h *histogram) Multiply(ratio float64) {
+	if h.valueCount == -1 {
+		for i := range h.buckets {
+			h.buckets[i] = int64(float64(h.buckets[i]) * ratio)
+		}
+	} else {
+		h.valueCount = int64(float64(h.valueCount) * ratio)
+	}
+	h.sum = int64(float64(h.sum) * ratio)
+	h.sumOfSquares = h.sumOfSquares * ratio
+}
+
+// New creates a new histogram.
+func (h *histogram) New() timeseries.Observable {
+	r := new(histogram)
+	r.Clear()
+	return r
+}
+
+func (h *histogram) String() string {
+	return fmt.Sprintf("%d, %f, %d, %d, %v",
+		h.sum, h.sumOfSquares, h.value, h.valueCount, h.buckets)
+}
+
+// round returns the closest int64 to the argument
+func round(in float64) int64 {
+	return int64(math.Floor(in + 0.5))
+}
+
+// bucketBoundary returns the first value in the bucket.
+func bucketBoundary(bucket uint8) int64 {
+	if bucket == 0 {
+		return 0
+	}
+	return 1 << bucket
+}
+
+// bucketData holds data about a specific bucket for use in distTmpl.
+type bucketData struct {
+	Lower, Upper       int64
+	N                  int64
+	Pct, CumulativePct float64
+	GraphWidth         int
+}
+
+// data holds data about a Distribution for use in distTmpl.
+type data struct {
+	Buckets                 []*bucketData
+	Count, Median           int64
+	Mean, StandardDeviation float64
+}
+
+// maxHTMLBarWidth is the maximum width of the HTML bar for visualizing buckets.
+const maxHTMLBarWidth = 350.0
+
+// newData returns data representing h for use in distTmpl.
+func (h *histogram) newData() *data {
+	// Force the allocation of buckets to simplify the rendering implementation
+	h.allocateBuckets()
+	// We scale the bars on the right so that the largest bar is
+	// maxHTMLBarWidth pixels in width.
+	maxBucket := int64(0)
+	for _, n := range h.buckets {
+		if n > maxBucket {
+			maxBucket = n
+		}
+	}
+	total := h.total()
+	barsizeMult := maxHTMLBarWidth / float64(maxBucket)
+	var pctMult float64
+	if total == 0 {
+		pctMult = 1.0
+	} else {
+		pctMult = 100.0 / float64(total)
+	}
+
+	buckets := make([]*bucketData, len(h.buckets))
+	runningTotal := int64(0)
+	for i, n := range h.buckets {
+		if n == 0 {
+			continue
+		}
+		runningTotal += n
+		var upperBound int64
+		if i < bucketCount-1 {
+			upperBound = bucketBoundary(uint8(i + 1))
+		} else {
+			upperBound = math.MaxInt64
+		}
+		buckets[i] = &bucketData{
+			Lower:         bucketBoundary(uint8(i)),
+			Upper:         upperBound,
+			N:             n,
+			Pct:           float64(n) * pctMult,
+			CumulativePct: float64(runningTotal) * pctMult,
+			GraphWidth:    int(float64(n) * barsizeMult),
+		}
+	}
+	return &data{
+		Buckets:           buckets,
+		Count:             total,
+		Median:            h.median(),
+		Mean:              h.average(),
+		StandardDeviation: h.standardDeviation(),
+	}
+}
+
+func (h *histogram) html() template.HTML {
+	buf := new(bytes.Buffer)
+	if err := distTmpl().Execute(buf, h.newData()); err != nil {
+		buf.Reset()
+		log.Printf("net/trace: couldn't execute template: %v", err)
+	}
+	return template.HTML(buf.String())
+}
+
+var distTmplCache *template.Template
+var distTmplOnce sync.Once
+
+func distTmpl() *template.Template {
+	distTmplOnce.Do(func() {
+		// Input: data
+		distTmplCache = template.Must(template.New("distTmpl").Parse(`
+<table>
+<tr>
+    <td style="padding:0.25em">Count: {{.Count}}</td>
+    <td style="padding:0.25em">Mean: {{printf "%.0f" .Mean}}</td>
+    <td style="padding:0.25em">StdDev: {{printf "%.0f" .StandardDeviation}}</td>
+    <td style="padding:0.25em">Median: {{.Median}}</td>
+</tr>
+</table>
+<hr>
+<table>
+{{range $b := .Buckets}}
+{{if $b}}
+  <tr>
+    <td style="padding:0 0 0 0.25em">[</td>
+    <td style="text-align:right;padding:0 0.25em">{{.Lower}},</td>
+    <td style="text-align:right;padding:0 0.25em">{{.Upper}})</td>
+    <td style="text-align:right;padding:0 0.25em">{{.N}}</td>
+    <td style="text-align:right;padding:0 0.25em">{{printf "%#.3f" .Pct}}%</td>
+    <td style="text-align:right;padding:0 0.25em">{{printf "%#.3f" .CumulativePct}}%</td>
+    <td><div style="background-color: blue; height: 1em; width: {{.GraphWidth}};"></div></td>
+  </tr>
+{{end}}
+{{end}}
+</table>
+`))
+	})
+	return distTmplCache
+}