cmd/trace: factor out durationHistogram

This code will be useful for the new tracer, and there's no need to
duplicate it. This change copies it to internal/trace/traceviewer, adds
some comments, and renames it to TimeHistogram.

While we're here, let's get rid of the unused String method which has a
comment talking about how awful the rendering is.

Also, let's get rid of uses of niceDuration. We'd have to bring it
with us in the move and I don't think it's worth it. The difference
between the default time.Duration rendering and the niceDuration
rendering is usually a few extra digits of precision. Yes, it's noisier,
but AFAICT it's not substantially worse. It doesn't seem worth the new
API, even if it's just internal. We can also always bring it back later.

For #60773.
For #63960.

Change-Id: I795f58f579f1d503c540c3a40bed12e52bce38e2
Reviewed-on: https://go-review.googlesource.com/c/go/+/542001
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Auto-Submit: Michael Knyszek <mknyszek@google.com>
Reviewed-by: Michael Pratt <mpratt@google.com>

1 files changed, 7 insertions, 120 deletions

diff --git a/src/cmd/trace/annotations.go b/src/cmd/trace/annotations.go
index 0addc240be..df194a7598 100644
--- a/src/cmd/trace/annotations.go
+++ b/src/cmd/trace/annotations.go
@@ -9,8 +9,8 @@ import (
 	"fmt"
 	"html/template"
 	"internal/trace"
+	"internal/trace/traceviewer"
 	"log"
-	"math"
 	"net/http"
 	"net/url"
 	"reflect"
@@ -808,122 +808,9 @@ func newRegionFilter(r *http.Request) (*regionFilter, error) {
 	}, nil
 }
 
-type durationHistogram struct {
-	Count                int
-	Buckets              []int
-	MinBucket, MaxBucket int
-}
-
-// Five buckets for every power of 10.
-var logDiv = math.Log(math.Pow(10, 1.0/5))
-
-func (h *durationHistogram) add(d time.Duration) {
-	var bucket int
-	if d > 0 {
-		bucket = int(math.Log(float64(d)) / logDiv)
-	}
-	if len(h.Buckets) <= bucket {
-		h.Buckets = append(h.Buckets, make([]int, bucket-len(h.Buckets)+1)...)
-		h.Buckets = h.Buckets[:cap(h.Buckets)]
-	}
-	h.Buckets[bucket]++
-	if bucket < h.MinBucket || h.MaxBucket == 0 {
-		h.MinBucket = bucket
-	}
-	if bucket > h.MaxBucket {
-		h.MaxBucket = bucket
-	}
-	h.Count++
-}
-
-func (h *durationHistogram) BucketMin(bucket int) time.Duration {
-	return time.Duration(math.Exp(float64(bucket) * logDiv))
-}
-
-func niceDuration(d time.Duration) string {
-	var rnd time.Duration
-	var unit string
-	switch {
-	case d < 10*time.Microsecond:
-		rnd, unit = time.Nanosecond, "ns"
-	case d < 10*time.Millisecond:
-		rnd, unit = time.Microsecond, "µs"
-	case d < 10*time.Second:
-		rnd, unit = time.Millisecond, "ms"
-	default:
-		rnd, unit = time.Second, "s "
-	}
-	return fmt.Sprintf("%d%s", d/rnd, unit)
-}
-
-func (h *durationHistogram) ToHTML(urlmaker func(min, max time.Duration) string) template.HTML {
-	if h == nil || h.Count == 0 {
-		return template.HTML("")
-	}
-
-	const barWidth = 400
-
-	maxCount := 0
-	for _, count := range h.Buckets {
-		if count > maxCount {
-			maxCount = count
-		}
-	}
-
-	w := new(strings.Builder)
-	fmt.Fprintf(w, `<table>`)
-	for i := h.MinBucket; i <= h.MaxBucket; i++ {
-		// Tick label.
-		if h.Buckets[i] > 0 {
-			fmt.Fprintf(w, `<tr><td class="histoTime" align="right"><a href=%s>%s</a></td>`, urlmaker(h.BucketMin(i), h.BucketMin(i+1)), niceDuration(h.BucketMin(i)))
-		} else {
-			fmt.Fprintf(w, `<tr><td class="histoTime" align="right">%s</td>`, niceDuration(h.BucketMin(i)))
-		}
-		// Bucket bar.
-		width := h.Buckets[i] * barWidth / maxCount
-		fmt.Fprintf(w, `<td><div style="width:%dpx;background:blue;position:relative">&nbsp;</div></td>`, width)
-		// Bucket count.
-		fmt.Fprintf(w, `<td align="right"><div style="position:relative">%d</div></td>`, h.Buckets[i])
-		fmt.Fprintf(w, "</tr>\n")
-
-	}
-	// Final tick label.
-	fmt.Fprintf(w, `<tr><td align="right">%s</td></tr>`, niceDuration(h.BucketMin(h.MaxBucket+1)))
-	fmt.Fprintf(w, `</table>`)
-	return template.HTML(w.String())
-}
-
-func (h *durationHistogram) String() string {
-	const barWidth = 40
-
-	labels := []string{}
-	maxLabel := 0
-	maxCount := 0
-	for i := h.MinBucket; i <= h.MaxBucket; i++ {
-		// TODO: This formatting is pretty awful.
-		label := fmt.Sprintf("[%-12s%-11s)", h.BucketMin(i).String()+",", h.BucketMin(i+1))
-		labels = append(labels, label)
-		if len(label) > maxLabel {
-			maxLabel = len(label)
-		}
-		count := h.Buckets[i]
-		if count > maxCount {
-			maxCount = count
-		}
-	}
-
-	w := new(strings.Builder)
-	for i := h.MinBucket; i <= h.MaxBucket; i++ {
-		count := h.Buckets[i]
-		bar := count * barWidth / maxCount
-		fmt.Fprintf(w, "%*s %-*s %d\n", maxLabel, labels[i-h.MinBucket], barWidth, strings.Repeat("█", bar), count)
-	}
-	return w.String()
-}
-
 type regionStats struct {
 	regionTypeID
-	Histogram durationHistogram
+	Histogram traceviewer.TimeHistogram
 }
 
 func (s *regionStats) UserRegionURL() func(min, max time.Duration) string {
@@ -933,7 +820,7 @@ func (s *regionStats) UserRegionURL() func(min, max time.Duration) string {
 }
 
 func (s *regionStats) add(region regionDesc) {
-	s.Histogram.add(region.duration())
+	s.Histogram.Add(region.duration())
 }
 
 var templUserRegionTypes = template.Must(template.New("").Parse(`
@@ -966,8 +853,8 @@ var templUserRegionTypes = template.Must(template.New("").Parse(`
 
 type taskStats struct {
 	Type      string
-	Count     int               // Complete + incomplete tasks
-	Histogram durationHistogram // Complete tasks only
+	Count     int                       // Complete + incomplete tasks
+	Histogram traceviewer.TimeHistogram // Complete tasks only
 }
 
 func (s *taskStats) UserTaskURL(complete bool) func(min, max time.Duration) string {
@@ -979,7 +866,7 @@ func (s *taskStats) UserTaskURL(complete bool) func(min, max time.Duration) stri
 func (s *taskStats) add(task *taskDesc) {
 	s.Count++
 	if task.complete() {
-		s.Histogram.add(task.duration())
+		s.Histogram.Add(task.duration())
 	}
 }
 
@@ -1169,7 +1056,7 @@ func isUserAnnotationEvent(ev *trace.Event) (taskID uint64, ok bool) {
 var templUserRegionType = template.Must(template.New("").Funcs(template.FuncMap{
 	"prettyDuration": func(nsec int64) template.HTML {
 		d := time.Duration(nsec) * time.Nanosecond
-		return template.HTML(niceDuration(d))
+		return template.HTML(d.String())
 	},
 	"percent": func(dividend, divisor int64) template.HTML {
 		if divisor == 0 {