forked from sampork/go-sniffer
-
Notifications
You must be signed in to change notification settings - Fork 0
/
ctxutil.go
93 lines (77 loc) · 2.82 KB
/
ctxutil.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
// Copyright 2021 FerretDB Inc.
//
// 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 ctxutil provides context helpers.
package ctxutil
import (
"context"
"fmt"
"math"
"math/rand"
"time"
)
// WithDelay returns a context that is canceled after a given amount of time after done channel is closed.
func WithDelay(done <-chan struct{}, delay time.Duration) (context.Context, context.CancelFunc) {
ctx, cancel := context.WithCancel(context.Background())
go func() {
select {
case <-ctx.Done():
return
case <-done:
t := time.NewTimer(delay)
defer t.Stop()
select {
case <-ctx.Done():
return
case <-t.C:
cancel()
}
}
}()
return ctx, cancel
}
// Sleep pauses the current goroutine until d has passed or ctx is canceled.
func Sleep(ctx context.Context, d time.Duration) {
sleepCtx, cancel := context.WithTimeout(ctx, d)
defer cancel()
<-sleepCtx.Done()
}
// SleepWithJitter pauses the current goroutine until d + jitter has passed or ctx is canceled.
func SleepWithJitter(ctx context.Context, d time.Duration, attempts int64) {
sleepCtx, cancel := context.WithTimeout(ctx, durationWithJitter(d, attempts))
defer cancel()
<-sleepCtx.Done()
}
// durationWithJitter returns an exponential backoff duration based on attempt with random "full jitter".
// https://aws.amazon.com/blogs/architecture/exponential-backoff-and-jitter/
//
// The maximum sleep is the cap. The minimum sleep is at least 3 milliseconds.
// Provided cap must be larger than minimum sleep, and attempt number must be a positive number.
func durationWithJitter(cap time.Duration, attempt int64) time.Duration {
const base = 100 // ms
const minDuration = 3 // ms
capDuration := cap.Milliseconds()
if attempt < 1 {
panic("attempt must be nonzero positive number")
}
if capDuration <= minDuration {
panic(fmt.Sprintf("cap must be larger than min duration (%dms)", minDuration))
}
// calculate base backoff based on base duration and amount of attempts
backoff := float64(base * math.Pow(2, float64(attempt)))
// cap is a max limit of possible durations returned
maxDuration := int64(math.Min(float64(capDuration), backoff))
// Math/rand is good enough because we don't need the randomness to be cryptographically secure.
sleep := rand.Int63n(maxDuration-minDuration) + minDuration
return time.Duration(sleep) * time.Millisecond
}