92 lines
1.8 KiB
Go
92 lines
1.8 KiB
Go
package pool
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import (
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"code.squareroundforest.org/arpio/times"
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"math"
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"time"
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)
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const (
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// arbitrary values to be most likely out of sync with anything else:
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minNightshiftTime = 729 * time.Millisecond // ~1sec
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maxNightshiftTime = 59049 * time.Second // ~2/3day
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)
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type adaptive struct {
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clock times.Clock
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activeTime time.Time
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nsTO time.Duration
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idle bool
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average float64
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deviation float64
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}
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func makeAdaptiveAlgo() *adaptive {
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return &adaptive{idle: true}
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}
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func (a *adaptive) setClock(c times.Clock) {
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a.clock = c
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}
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func movingAverage(prev, currv float64) float64 {
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return prev + (currv-prev)/math.E
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}
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func movingAbsoluteDeviation(prev, currv, currav float64) float64 {
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return prev + (math.Abs(currv-currav)-prev)/math.E
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}
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func targetCapacity(av, dev float64) float64 {
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return av + dev*math.E
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}
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func (a *adaptive) target(s Stats) int {
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av := movingAverage(a.average, float64(s.Active))
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dev := movingAbsoluteDeviation(a.deviation, float64(s.Active), av)
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a.average = av
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a.deviation = dev
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return int(targetCapacity(av, dev))
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}
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func (a *adaptive) nightshift(s Stats) time.Duration {
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if a.idle && s.Active == 0 {
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return a.nsTO
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}
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if !a.idle && s.Active > 0 {
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return 0
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}
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now := a.clock.Now()
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a.idle = !a.idle
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if !a.idle {
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a.activeTime = now
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return 0
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}
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a.nsTO = now.Sub(a.activeTime)
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a.nsTO = (3 * a.nsTO) / 8
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if a.nsTO < minNightshiftTime {
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a.nsTO = minNightshiftTime
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}
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if a.nsTO > maxNightshiftTime {
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a.nsTO = maxNightshiftTime
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}
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return a.nsTO
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}
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func (a *adaptive) Target(s Stats) (int, time.Duration) {
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t := a.target(s)
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ns := a.nightshift(s)
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return t, ns
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}
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func (a *adaptive) Load(n int) {
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// we lie to the algorithm when adding the additional idle count to the average active count. This way
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// we can adjust the calculated target capacity:
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a.average += float64(n)
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}
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