Binary Exponential Back-Off Scheduler in Go

bebo.go

// BEBOSchedule computes a Binary Exponential Back-Off schedule given the following:
// 	retries:  maximum number of retry attempts
// 	waittime: maximum number of seconds from the first attempt after which the operation is permanently failed
//
// The schedule is returned as a list of seconds since first attempt at which a retry must be made
// The schedule will have as many entries as the maximum number of attempts given

func BEBOSchedule(retries, waittime int) ([]uint, error) {
	if retries <= 0 || waittime <= 0 || waittime < 1<<uint(retries)-1 {
		return []uint{}, fmt.Errorf("Invalid retries or waittime")
	}

	r, t := uint(retries), uint(waittime)
	i := t / (1<<r - 1)
	if i == 0 {
		return []uint{}, fmt.Errorf("Too many retries in too little time")
	}
	c := i
	sched := []uint{}

	for c <= t {
		sched = append(sched, c)
		i *= 2
		c += i
	}

	return sched, nil
}