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
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
|
package resources
import (
"sync"
"time"
)
type WithTimestamp interface {
Timestamp() time.Time
}
type Sampler[T WithTimestamp] struct {
mu sync.Mutex
minInterval time.Duration
maxSamples int
callback func(ts time.Time) (T, error)
doneOnce sync.Once
done chan struct{}
running bool
subs map[*Sub[T]]struct{}
}
type Sub[T WithTimestamp] struct {
sampler *Sampler[T]
interval time.Duration
first time.Time
last time.Time
samples []T
err error
}
func (s *Sub[T]) Close(captureLast bool) ([]T, error) {
s.sampler.mu.Lock()
delete(s.sampler.subs, s)
if s.err != nil {
s.sampler.mu.Unlock()
return nil, s.err
}
current := s.first
out := make([]T, 0, len(s.samples)+1)
for i, v := range s.samples {
ts := v.Timestamp()
if i == 0 || ts.Sub(current) >= s.interval {
out = append(out, v)
current = ts
}
}
s.sampler.mu.Unlock()
if captureLast {
v, err := s.sampler.callback(time.Now())
if err != nil {
return nil, err
}
out = append(out, v)
}
return out, nil
}
func NewSampler[T WithTimestamp](minInterval time.Duration, maxSamples int, cb func(time.Time) (T, error)) *Sampler[T] {
s := &Sampler[T]{
minInterval: minInterval,
maxSamples: maxSamples,
callback: cb,
done: make(chan struct{}),
subs: make(map[*Sub[T]]struct{}),
}
return s
}
func (s *Sampler[T]) Record() *Sub[T] {
ss := &Sub[T]{
interval: s.minInterval,
first: time.Now(),
sampler: s,
}
s.mu.Lock()
s.subs[ss] = struct{}{}
if !s.running {
s.running = true
go s.run()
}
s.mu.Unlock()
return ss
}
func (s *Sampler[T]) run() {
ticker := time.NewTimer(s.minInterval)
for {
select {
case <-s.done:
ticker.Stop()
return
case <-ticker.C:
tm := time.Now()
s.mu.Lock()
active := make([]*Sub[T], 0, len(s.subs))
for ss := range s.subs {
if tm.Sub(ss.last) < ss.interval {
continue
}
ss.last = tm
active = append(active, ss)
}
s.mu.Unlock()
ticker = time.NewTimer(s.minInterval)
if len(active) == 0 {
continue
}
value, err := s.callback(tm)
s.mu.Lock()
for _, ss := range active {
if _, found := s.subs[ss]; !found {
continue // skip if Close() was called while the lock was released
}
if err != nil {
ss.err = err
} else {
ss.samples = append(ss.samples, value)
ss.err = nil
}
dur := ss.last.Sub(ss.first)
if time.Duration(ss.interval)*time.Duration(s.maxSamples) <= dur {
ss.interval *= 2
}
}
s.mu.Unlock()
}
}
}
func (s *Sampler[T]) Close() error {
s.doneOnce.Do(func() {
close(s.done)
})
return nil
}
|
