traefik/vendor/github.com/vulcand/oxy/cbreaker/ratio.go
Ludovic Fernandez 38a4c80995 Logger and Leaks
2018-02-12 17:24:03 +01:00

70 lines
1.8 KiB
Go

package cbreaker
import (
"fmt"
"time"
"github.com/mailgun/timetools"
log "github.com/sirupsen/logrus"
)
// ratioController allows passing portions traffic back to the endpoints,
// increasing the amount of passed requests using linear function:
//
// allowedRequestsRatio = 0.5 * (Now() - Start())/Duration
//
type ratioController struct {
duration time.Duration
start time.Time
tm timetools.TimeProvider
allowed int
denied int
}
func newRatioController(tm timetools.TimeProvider, rampUp time.Duration) *ratioController {
return &ratioController{
duration: rampUp,
tm: tm,
start: tm.UtcNow(),
}
}
func (r *ratioController) String() string {
return fmt.Sprintf("RatioController(target=%f, current=%f, allowed=%d, denied=%d)", r.targetRatio(), r.computeRatio(r.allowed, r.denied), r.allowed, r.denied)
}
func (r *ratioController) allowRequest() bool {
log.Debugf("%v", r)
t := r.targetRatio()
// This condition answers the question - would we satisfy the target ratio if we allow this request?
e := r.computeRatio(r.allowed+1, r.denied)
if e < t {
r.allowed++
log.Debugf("%v allowed", r)
return true
}
r.denied++
log.Debugf("%v denied", r)
return false
}
func (r *ratioController) computeRatio(allowed, denied int) float64 {
if denied+allowed == 0 {
return 0
}
return float64(allowed) / float64(denied+allowed)
}
func (r *ratioController) targetRatio() float64 {
// Here's why it's 0.5:
// We are watching the following ratio
// ratio = a / (a + d)
// We can notice, that once we get to 0.5
// 0.5 = a / (a + d)
// we can evaluate that a = d
// that means equilibrium, where we would allow all the requests
// after this point to achieve ratio of 1 (that can never be reached unless d is 0)
// so we stop from there
multiplier := 0.5 / float64(r.duration)
return multiplier * float64(r.tm.UtcNow().Sub(r.start))
}