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delay.go
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delay.go
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// Copyright 2020 The searKing Author. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package time
// Deprecated: Use BackOff instead.
//
//import (
// "math/rand"
// "time"
//)
//
//const DefaultBaseDuration = 5 * time.Millisecond
//const DefaultMaxDuration = 1 * time.Second
//
//const ZeroDuration = 0
//
//type DelayHandler interface {
// Delay(attempt int, cap, base, last time.Duration) (delay time.Duration)
//}
//
//// The HandlerFunc type is an adapter to allow the use of
//// ordinary functions as HTTP handlers. If f is a function
//// with the appropriate signature, HandlerFunc(f) is a
//// Handler that calls f.
//type DelayHandlerFunc func(attempt int, cap, base, last time.Duration) (delay time.Duration)
//
//// ServeHTTP calls f(w, r).
//func (f DelayHandlerFunc) Delay(attempt int, cap, base, last time.Duration) (delay time.Duration) {
// return f(attempt, cap, base, last)
//}
//
//// Exponential backoff is an algorithm that uses feedback to multiplicatively decrease the rate of some process,
//// in order to gradually find an acceptable rate
//// see https://cloud.google.com/iot/docs/how-tos/exponential-backoff
//// see https://amazonaws-china.com/cn/blogs/architecture/exponential-backoff-and-jitter/
//
//// Work(calls) of Competing Clients(less is better)
//// None > Exponential > DecorrelatedJitter > EqualJitter > FullJitter
//// Looking at the amount of client work, the number of calls is approximately the same for “Full” and “Equal” jitter,
//// and higher for “Decorrelated”. Both cut down work substantially relative to both the no-jitter approaches.
//
//// Completion Time(ms) of Competing Clients(less is better)
//// Exponential > EqualJitter > FullJitter > DecorrelatedJitter > None
//
//// none backed-off
//// sleep = min(cap, base)
//func NoneBackOffDelayHandler(_ int, cap, base, _ time.Duration) time.Duration {
// delay := base
// if delay > cap {
// delay = cap
// }
// return delay
//}
//
//// exponentially backed-off
//// sleep = min(cap, base * 2 ** attempt)
//func ExponentialDelayHandler(attempt int, cap, base, _ time.Duration) time.Duration {
// delay := base * (2 << attempt)
// if delay > cap {
// delay = cap
// }
// return delay
//}
//
//// exponentially backed-off with full jitter
//// sleep = random_between(0, min(cap, base * 2 ** attempt))
//func FullJitterDelayHandler(attempt int, cap, base, _ time.Duration) time.Duration {
// delay := base * (2 << attempt)
// if delay > cap {
// delay = cap
// }
// return time.Duration(rand.Float64() * float64(delay))
//}
//
//// exponentially backed-off with equal jitter
//// temp = min(cap, base * 2 ** attempt)
//// sleep = temp/2 + random_between(temp/2, min(cap, base * 2 ** attempt))
//func EqualJitterDelayHandler(attempt int, cap, base, _ time.Duration) time.Duration {
// temp := base * (2 << attempt)
// if temp > cap {
// temp = cap
// }
// delay := temp / 2
// return delay + time.Duration(float64(delay)+rand.Float64()*float64(delay))
//}
//
//// exponentially backed-off with decorrelated jitter
//// sleep = min(cap, random_between(base, sleep * 3))
//func DecorrelatedJitterDelayHandler(_ int, cap, base, last time.Duration) time.Duration {
// delay := base + time.Duration(rand.Float64()*float64(last*3-base))
// if delay > cap {
// delay = cap
// }
// return delay
//}
//
//func NewDelay(base, cap time.Duration, h DelayHandler) *Delay {
// return &Delay{
// Base: base,
// Cap: cap,
// Handler: h,
// }
//}
//
//func NewDefaultExponentialDelay() *Delay {
// return &Delay{
// Base: DefaultBaseDuration,
// Cap: DefaultMaxDuration,
// Handler: DelayHandlerFunc(ExponentialDelayHandler),
// }
//}
//
//type Delay struct {
// attempt int
// delay time.Duration
// Base time.Duration
// Cap time.Duration
// Handler DelayHandler
//}
//
//func (d *Delay) Update() {
// defer func() { d.attempt++ }()
// h := d.Handler
// if h == nil {
// h = DelayHandlerFunc(NoneBackOffDelayHandler)
// }
//
// d.delay = h.Delay(d.attempt, d.Cap, d.Base, d.delay)
// if max := d.Cap; d.delay > max {
// d.delay = max
// }
//}
//
//func (d *Delay) Sleep() {
// d.Update()
// time.Sleep(d.delay)
//}
//
//func (d *Delay) Delay() <-chan time.Time {
// d.Update()
// return After(d.delay)
//}
//
//func (d *Delay) DelayFunc(f func()) *Timer {
// d.Update()
// return AfterFunc(d.delay, f)
//}
//
//// Reset to initial state.
//func (d *Delay) Reset() {
// d.delay = ZeroDuration
// d.attempt = 0
//}
//
//// Gets duration to wait before retrying the operation or {@link #STOP} to
//// indicate that no retries should be made.
//func (d *Delay) NextBackOff() (backoff time.Duration, ok bool) {
// d.Update()
// return d.delay, ok
//}