forked from distribution/distribution
-
Notifications
You must be signed in to change notification settings - Fork 2
/
stats.go
116 lines (100 loc) · 2.71 KB
/
stats.go
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
package stats
import (
"bytes"
"fmt"
"io"
"math"
"time"
)
// Stats is a simple helper for gathering additional statistics like histogram
// during benchmarks. This is not thread safe.
type Stats struct {
numBuckets int
unit time.Duration
min, max int64
histogram *Histogram
durations durationSlice
dirty bool
}
type durationSlice []time.Duration
// NewStats creates a new Stats instance. If numBuckets is not positive,
// the default value (16) will be used.
func NewStats(numBuckets int) *Stats {
if numBuckets <= 0 {
numBuckets = 16
}
return &Stats{
// Use one more bucket for the last unbounded bucket.
numBuckets: numBuckets + 1,
durations: make(durationSlice, 0, 100000),
}
}
// Add adds an elapsed time per operation to the stats.
func (stats *Stats) Add(d time.Duration) {
stats.durations = append(stats.durations, d)
stats.dirty = true
}
// Clear resets the stats, removing all values.
func (stats *Stats) Clear() {
stats.durations = stats.durations[:0]
stats.histogram = nil
stats.dirty = false
}
// maybeUpdate updates internal stat data if there was any newly added
// stats since this was updated.
func (stats *Stats) maybeUpdate() {
if !stats.dirty {
return
}
stats.min = math.MaxInt64
stats.max = 0
for _, d := range stats.durations {
if stats.min > int64(d) {
stats.min = int64(d)
}
if stats.max < int64(d) {
stats.max = int64(d)
}
}
// Use the largest unit that can represent the minimum time duration.
stats.unit = time.Nanosecond
for _, u := range []time.Duration{time.Microsecond, time.Millisecond, time.Second} {
if stats.min <= int64(u) {
break
}
stats.unit = u
}
// Adjust the min/max according to the new unit.
stats.min /= int64(stats.unit)
stats.max /= int64(stats.unit)
numBuckets := stats.numBuckets
if n := int(stats.max - stats.min + 1); n < numBuckets {
numBuckets = n
}
stats.histogram = NewHistogram(HistogramOptions{
NumBuckets: numBuckets,
// max(i.e., Nth lower bound) = min + (1 + growthFactor)^(numBuckets-2).
GrowthFactor: math.Pow(float64(stats.max-stats.min), 1/float64(stats.numBuckets-2)) - 1,
SmallestBucketSize: 1.0,
MinValue: stats.min})
for _, d := range stats.durations {
stats.histogram.Add(int64(d / stats.unit))
}
stats.dirty = false
}
// Print writes textual output of the Stats.
func (stats *Stats) Print(w io.Writer) {
stats.maybeUpdate()
if stats.histogram == nil {
fmt.Fprint(w, "Histogram (empty)\n")
} else {
fmt.Fprintf(w, "Histogram (unit: %s)\n", fmt.Sprintf("%v", stats.unit)[1:])
stats.histogram.Value().Print(w)
}
}
// String returns the textual output of the Stats as string.
func (stats *Stats) String() string {
var b bytes.Buffer
stats.Print(&b)
return b.String()
}