1package libkb 2 3// from here: 4// https://blog.gopheracademy.com/advent-2014/backoff/ 5 6import ( 7 "math/rand" 8 "time" 9) 10 11// BackoffPolicy implements a backoff policy, randomizing its delays 12// and saturating at the final value in Millis. 13type BackoffPolicy struct { 14 Millis []int 15} 16 17// BackoffDefault is a backoff policy ranging up to 5 seconds. 18var BackoffDefault = BackoffPolicy{ 19 []int{0, 10, 10, 100, 100, 500, 500, 3000, 3000, 5000}, 20} 21 22// Duration returns the time duration of the n'th wait cycle in a 23// backoff policy. This is b.Millis[n], randomized to avoid thundering 24// herds. 25func (b BackoffPolicy) Duration(n int) time.Duration { 26 if n >= len(b.Millis) { 27 n = len(b.Millis) - 1 28 } 29 30 return time.Duration(jitter(b.Millis[n])) * time.Millisecond 31} 32 33// jitter returns a random integer uniformly distributed in the range 34// [0.5 * millis .. 1.5 * millis] 35func jitter(millis int) int { 36 if millis == 0 { 37 return 0 38 } 39 40 return millis/2 + rand.Intn(millis) 41} 42