mirror of https://github.com/k3s-io/k3s
90 lines
3.1 KiB
Go
90 lines
3.1 KiB
Go
// Package jitter provides methods of transforming durations.
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//
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// Copyright © 2016 Trevor N. Suarez (Rican7)
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package jitter
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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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// Transformation defines a function that calculates a time.Duration based on
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// the given duration.
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type Transformation func(duration time.Duration) time.Duration
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// Full creates a Transformation that transforms a duration into a result
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// duration in [0, n) randomly, where n is the given duration.
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//
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// The given generator is what is used to determine the random transformation.
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// If a nil generator is passed, a default one will be provided.
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//
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// Inspired by https://www.awsarchitectureblog.com/2015/03/backoff.html
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func Full(generator *rand.Rand) Transformation {
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random := fallbackNewRandom(generator)
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return func(duration time.Duration) time.Duration {
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return time.Duration(random.Int63n(int64(duration)))
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}
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}
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// Equal creates a Transformation that transforms a duration into a result
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// duration in [n/2, n) randomly, where n is the given duration.
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//
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// The given generator is what is used to determine the random transformation.
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// If a nil generator is passed, a default one will be provided.
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//
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// Inspired by https://www.awsarchitectureblog.com/2015/03/backoff.html
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func Equal(generator *rand.Rand) Transformation {
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random := fallbackNewRandom(generator)
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return func(duration time.Duration) time.Duration {
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return (duration / 2) + time.Duration(random.Int63n(int64(duration))/2)
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}
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}
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// Deviation creates a Transformation that transforms a duration into a result
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// duration that deviates from the input randomly by a given factor.
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//
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// The given generator is what is used to determine the random transformation.
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// If a nil generator is passed, a default one will be provided.
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//
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// Inspired by https://developers.google.com/api-client-library/java/google-http-java-client/backoff
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func Deviation(generator *rand.Rand, factor float64) Transformation {
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random := fallbackNewRandom(generator)
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return func(duration time.Duration) time.Duration {
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min := int64(math.Floor(float64(duration) * (1 - factor)))
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max := int64(math.Ceil(float64(duration) * (1 + factor)))
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return time.Duration(random.Int63n(max-min) + min)
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}
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}
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// NormalDistribution creates a Transformation that transforms a duration into a
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// result duration based on a normal distribution of the input and the given
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// standard deviation.
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//
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// The given generator is what is used to determine the random transformation.
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// If a nil generator is passed, a default one will be provided.
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func NormalDistribution(generator *rand.Rand, standardDeviation float64) Transformation {
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random := fallbackNewRandom(generator)
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return func(duration time.Duration) time.Duration {
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return time.Duration(random.NormFloat64()*standardDeviation + float64(duration))
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}
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}
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// fallbackNewRandom returns the passed in random instance if it's not nil,
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// and otherwise returns a new random instance seeded with the current time.
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func fallbackNewRandom(random *rand.Rand) *rand.Rand {
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// Return the passed in value if it's already not null
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if nil != random {
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return random
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}
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seed := time.Now().UnixNano()
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return rand.New(rand.NewSource(seed))
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}
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