forked from ipfs/go-bitswap
/
internet_latency_delay_generator.go
63 lines (56 loc) · 1.94 KB
/
internet_latency_delay_generator.go
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package bitswap
import (
"math/rand"
"time"
"github.com/ipfs/go-ipfs-delay"
)
var sharedRNG = rand.New(rand.NewSource(time.Now().UnixNano()))
// InternetLatencyDelayGenerator generates three clusters of delays,
// typical of the type of peers you would encounter on the interenet.
// Given a base delay time T, the wait time generated will be either:
// 1. A normalized distribution around the base time
// 2. A normalized distribution around the base time plus a "medium" delay
// 3. A normalized distribution around the base time plus a "large" delay
// The size of the medium & large delays are determined when the generator
// is constructed, as well as the relative percentages with which delays fall
// into each of the three different clusters, and the standard deviation for
// the normalized distribution.
// This can be used to generate a number of scenarios typical of latency
// distribution among peers on the internet.
func InternetLatencyDelayGenerator(
mediumDelay time.Duration,
largeDelay time.Duration,
percentMedium float64,
percentLarge float64,
std time.Duration,
rng *rand.Rand) delay.Generator {
if rng == nil {
rng = sharedRNG
}
return &internetLatencyDelayGenerator{
mediumDelay: mediumDelay,
largeDelay: largeDelay,
percentLarge: percentLarge,
percentMedium: percentMedium,
std: std,
rng: rng,
}
}
type internetLatencyDelayGenerator struct {
mediumDelay time.Duration
largeDelay time.Duration
percentLarge float64
percentMedium float64
std time.Duration
rng *rand.Rand
}
func (d *internetLatencyDelayGenerator) NextWaitTime(t time.Duration) time.Duration {
clusterDistribution := d.rng.Float64()
baseDelay := time.Duration(d.rng.NormFloat64()*float64(d.std)) + t
if clusterDistribution < d.percentLarge {
return baseDelay + d.largeDelay
} else if clusterDistribution < d.percentMedium+d.percentLarge {
return baseDelay + d.mediumDelay
}
return baseDelay
}