Vendor main dependencies.

vendor/github.com/vulcand/oxy/cbreaker/ratio.go

@@ -0,0 +1,66 @@
+package cbreaker
+
+import (
+	"fmt"
+	"time"
+
+	"github.com/mailgun/timetools"
+)
+
+// 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 {
+	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++
+		return true
+	}
+	r.denied++
+	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))
+}