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package slack
import (
"math"
"math/rand"
"time"
)
// This one was ripped from https://github.com/jpillora/backoff/blob/master/backoff.go
// Backoff is a time.Duration counter. It starts at Min. After every
// call to Duration() it is multiplied by Factor. It is capped at
// Max. It returns to Min on every call to Reset(). Used in
// conjunction with the time package.
type backoff struct {
attempts int
//Factor is the multiplying factor for each increment step
Factor float64
//Jitter eases contention by randomizing backoff steps
Jitter bool
//Min and Max are the minimum and maximum values of the counter
Min, Max time.Duration
}
// Returns the current value of the counter and then multiplies it
// Factor
func (b *backoff) Duration() time.Duration {
//Zero-values are nonsensical, so we use
//them to apply defaults
if b.Min == 0 {
b.Min = 100 * time.Millisecond
}
if b.Max == 0 {
b.Max = 10 * time.Second
}
if b.Factor == 0 {
b.Factor = 2
}
//calculate this duration
dur := float64(b.Min) * math.Pow(b.Factor, float64(b.attempts))
if b.Jitter {
dur = rand.Float64()*(dur-float64(b.Min)) + float64(b.Min)
}
//cap!
if dur > float64(b.Max) {
return b.Max
}
//bump attempts count
b.attempts++
//return as a time.Duration
return time.Duration(dur)
}
//Resets the current value of the counter back to Min
func (b *backoff) Reset() {
b.attempts = 0
}
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