jitter.go

Documentation: github.com/lestrrat-go/backoff/v2

     1  package backoff
     2  
     3  import (
     4  	"math/rand"
     5  	"time"
     6  )
     7  
     8  type jitter interface {
     9  	apply(interval float64) float64
    10  }
    11  
    12  func newJitter(jitterFactor float64, rng Random) jitter {
    13  	if jitterFactor <= 0 || jitterFactor >= 1 {
    14  		return newNopJitter()
    15  	}
    16  	return newRandomJitter(jitterFactor, rng)
    17  }
    18  
    19  type nopJitter struct{}
    20  
    21  func newNopJitter() *nopJitter {
    22  	return &nopJitter{}
    23  }
    24  
    25  func (j *nopJitter) apply(interval float64) float64 {
    26  	return interval
    27  }
    28  
    29  type randomJitter struct {
    30  	jitterFactor float64
    31  	rng          Random
    32  }
    33  
    34  func newRandomJitter(jitterFactor float64, rng Random) *randomJitter {
    35  	if rng == nil {
    36  		// if we have a jitter factor, and no RNG is provided, create one.
    37  		// This is definitely not "secure", but well, if you care enough,
    38  		// you would provide one
    39  		rng = rand.New(rand.NewSource(time.Now().UnixNano()))
    40  	}
    41  
    42  	return &randomJitter{
    43  		jitterFactor: jitterFactor,
    44  		rng:          rng,
    45  	}
    46  }
    47  
    48  func (j *randomJitter) apply(interval float64) float64 {
    49  	jitterDelta := interval * j.jitterFactor
    50  	jitterMin := interval - jitterDelta
    51  	jitterMax := interval + jitterDelta
    52  
    53  	// Get a random value from the range [minInterval, maxInterval].
    54  	// The formula used below has a +1 because if the minInterval is 1 and the maxInterval is 3 then
    55  	// we want a 33% chance for selecting either 1, 2 or 3.
    56  	//
    57  	// see also: https://github.com/cenkalti/backoff/blob/c2975ffa541a1caeca5f76c396cb8c3e7b3bb5f8/exponential.go#L154-L157
    58  	return jitterMin + j.rng.Float64()*(jitterMax-jitterMin+1)
    59  }
    60
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