mirror of
https://github.com/restic/restic.git
synced 2024-08-18 02:13:23 +02:00
99 lines
3.0 KiB
Go
99 lines
3.0 KiB
Go
package backup
|
|
|
|
import (
|
|
"container/list"
|
|
"time"
|
|
)
|
|
|
|
// rateBucket represents a one second window of recorded progress.
|
|
type rateBucket struct {
|
|
totalBytes uint64
|
|
end time.Time // the end of the time window, exclusive
|
|
}
|
|
|
|
// rateEstimator represents an estimate of the time to complete an operation.
|
|
type rateEstimator struct {
|
|
buckets *list.List
|
|
start time.Time
|
|
totalBytes uint64
|
|
}
|
|
|
|
// newRateEstimator returns an estimator initialized to a presumed start time.
|
|
func newRateEstimator(start time.Time) *rateEstimator {
|
|
return &rateEstimator{buckets: list.New(), start: start}
|
|
}
|
|
|
|
// See trim(), below.
|
|
const (
|
|
bucketWidth = time.Second
|
|
minRateEstimatorBytes = 100 * 1000 * 1000
|
|
minRateEstimatorBuckets = 20
|
|
minRateEstimatorMinutes = 2
|
|
)
|
|
|
|
// trim removes the oldest history from the estimator assuming a given
|
|
// current time.
|
|
func (r *rateEstimator) trim(now time.Time) {
|
|
// The estimator retains byte transfer counts over a two minute window.
|
|
// However, to avoid removing too much history when transfer rates are
|
|
// low, the estimator also retains a minimum number of processed bytes
|
|
// across a minimum number of buckets. An operation that is processing a
|
|
// significant number of bytes per second will typically retain only a
|
|
// two minute window's worth of information. One that is making slow
|
|
// progress, such as one being over a rate limited connection, typically
|
|
// observes bursts of updates as infrequently as every ten or twenty
|
|
// seconds, in which case the other limiters will kick in. This heuristic
|
|
// avoids wildly fluctuating estimates over rate limited connections.
|
|
start := now.Add(-minRateEstimatorMinutes * time.Minute)
|
|
|
|
for e := r.buckets.Front(); e != nil; e = r.buckets.Front() {
|
|
if r.buckets.Len() <= minRateEstimatorBuckets {
|
|
break
|
|
}
|
|
b := e.Value.(*rateBucket)
|
|
if b.end.After(start) {
|
|
break
|
|
}
|
|
total := r.totalBytes - b.totalBytes
|
|
if total < minRateEstimatorBytes {
|
|
break
|
|
}
|
|
r.start = b.end
|
|
r.totalBytes = total
|
|
r.buckets.Remove(e)
|
|
}
|
|
}
|
|
|
|
// recordBytes records the transfer of a number of bytes at a given
|
|
// time. Times passed in successive calls should advance monotonically (as
|
|
// is the case with time.Now().
|
|
func (r *rateEstimator) recordBytes(now time.Time, bytes uint64) {
|
|
if bytes == 0 {
|
|
return
|
|
}
|
|
var tail *rateBucket
|
|
if r.buckets.Len() > 0 {
|
|
tail = r.buckets.Back().Value.(*rateBucket)
|
|
}
|
|
if tail == nil || !tail.end.After(now) {
|
|
// The new bucket holds measurements in the time range [now .. now+1sec).
|
|
tail = &rateBucket{end: now.Add(bucketWidth)}
|
|
r.buckets.PushBack(tail)
|
|
}
|
|
tail.totalBytes += bytes
|
|
r.totalBytes += bytes
|
|
r.trim(now)
|
|
}
|
|
|
|
// rate returns an estimated bytes per second rate at a given time, or zero
|
|
// if there is not enough data to compute a rate.
|
|
func (r *rateEstimator) rate(now time.Time) float64 {
|
|
r.trim(now)
|
|
if !r.start.Before(now) {
|
|
return 0
|
|
}
|
|
elapsed := float64(now.Sub(r.start)) / float64(time.Second)
|
|
rate := float64(r.totalBytes) / elapsed
|
|
return rate
|
|
}
|