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package backoff
import (
"math/rand"
"time"
)
type jitter interface {
apply(interval float64) float64
}
func newJitter(jitterFactor float64, rng Random) jitter {
if jitterFactor <= 0 || jitterFactor >= 1 {
return newNopJitter()
}
return newRandomJitter(jitterFactor, rng)
}
type nopJitter struct{}
func newNopJitter() *nopJitter {
return &nopJitter{}
}
func (j *nopJitter) apply(interval float64) float64 {
return interval
}
type randomJitter struct {
jitterFactor float64
rng Random
}
func newRandomJitter(jitterFactor float64, rng Random) *randomJitter {
if rng == nil {
// if we have a jitter factor, and no RNG is provided, create one.
// This is definitely not "secure", but well, if you care enough,
// you would provide one
rng = rand.New(rand.NewSource(time.Now().UnixNano()))
}
return &randomJitter{
jitterFactor: jitterFactor,
rng: rng,
}
}
func (j *randomJitter) apply(interval float64) float64 {
jitterDelta := interval * j.jitterFactor
jitterMin := interval - jitterDelta
jitterMax := interval + jitterDelta
// Get a random value from the range [minInterval, maxInterval].
// The formula used below has a +1 because if the minInterval is 1 and the maxInterval is 3 then
// we want a 33% chance for selecting either 1, 2 or 3.
//
// see also: https://github.com/cenkalti/backoff/blob/c2975ffa541a1caeca5f76c396cb8c3e7b3bb5f8/exponential.go#L154-L157
return jitterMin + j.rng.Float64()*(jitterMax-jitterMin+1)
}
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