forked from cadey/xesite
84 lines
1.7 KiB
Go
84 lines
1.7 KiB
Go
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package backo
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import (
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"math"
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"math/rand"
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"time"
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)
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type Backo struct {
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base time.Duration
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factor uint8
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jitter float64
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cap time.Duration
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}
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// Creates a backo instance with the given parameters
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func NewBacko(base time.Duration, factor uint8, jitter float64, cap time.Duration) *Backo {
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return &Backo{base, factor, jitter, cap}
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}
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// Creates a backo instance with the following defaults:
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// base: 100 milliseconds
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// factor: 2
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// jitter: 0
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// cap: 10 seconds
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func DefaultBacko() *Backo {
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return NewBacko(time.Millisecond*100, 2, 0, time.Second*10)
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}
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// Duration returns the backoff interval for the given attempt.
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func (backo *Backo) Duration(attempt int) time.Duration {
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duration := float64(backo.base) * math.Pow(float64(backo.factor), float64(attempt))
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if backo.jitter != 0 {
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random := rand.Float64()
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deviation := math.Floor(random * backo.jitter * duration)
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if (int(math.Floor(random*10)) & 1) == 0 {
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duration = duration - deviation
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} else {
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duration = duration + deviation
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}
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}
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duration = math.Min(float64(duration), float64(backo.cap))
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return time.Duration(duration)
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}
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// Sleep pauses the current goroutine for the backoff interval for the given attempt.
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func (backo *Backo) Sleep(attempt int) {
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duration := backo.Duration(attempt)
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time.Sleep(duration)
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}
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type Ticker struct {
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done chan struct{}
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C <-chan time.Time
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}
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func (b *Backo) NewTicker() *Ticker {
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c := make(chan time.Time, 1)
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ticker := &Ticker{
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done: make(chan struct{}, 1),
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C: c,
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}
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go func() {
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for i := 0; ; i++ {
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select {
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case t := <-time.After(b.Duration(i)):
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c <- t
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case <-ticker.done:
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close(c)
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return
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}
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}
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}()
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return ticker
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}
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func (t *Ticker) Stop() {
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t.done <- struct{}{}
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}
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