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