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delay.go
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delay.go
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package delay
import (
"math/rand"
"sync"
"time"
)
var sharedRNG = rand.New(rand.NewSource(time.Now().UnixNano()))
// Delay makes it easy to add (threadsafe) configurable delays to other
// objects.
type D interface {
Set(time.Duration) time.Duration
Wait()
Get() time.Duration
}
// Fixed returns a delay with fixed latency
func Fixed(t time.Duration) D {
return &delay{t: t}
}
type delay struct {
l sync.RWMutex
t time.Duration
}
func (d *delay) Set(t time.Duration) time.Duration {
d.l.Lock()
defer d.l.Unlock()
prev := d.t
d.t = t
return prev
}
func (d *delay) Wait() {
d.l.RLock()
defer d.l.RUnlock()
time.Sleep(d.t)
}
func (d *delay) Get() time.Duration {
d.l.Lock()
defer d.l.Unlock()
return d.t
}
// VariableNormal is a delay following a normal distribution
// Notice that to implement the D interface Set can only change the mean delay
// the standard deviation is set only at initialization
func VariableNormal(t, std time.Duration, rng *rand.Rand) D {
if rng == nil {
rng = sharedRNG
}
v := &variableNormal{
std: std,
rng: rng,
}
v.t = t
return v
}
type variableNormal struct {
delay
std time.Duration
rng *rand.Rand
}
func (d *variableNormal) Wait() {
d.l.RLock()
defer d.l.RUnlock()
randomDelay := time.Duration(d.rng.NormFloat64() * float64(d.std))
time.Sleep(randomDelay + d.t)
}
// VariableUniform is a delay following a uniform distribution
// Notice that to implement the D interface Set can only change the minimum delay
// the delta is set only at initialization
func VariableUniform(t, d time.Duration, rng *rand.Rand) D {
if rng == nil {
rng = sharedRNG
}
v := &variableUniform{
d: d,
rng: rng,
}
v.t = t
return v
}
type variableUniform struct {
delay
d time.Duration // max delta
rng *rand.Rand
}
func (d *variableUniform) Wait() {
d.l.RLock()
defer d.l.RUnlock()
randomDelay := time.Duration(d.rng.Float64() * float64(d.d))
time.Sleep(randomDelay + d.t)
}