add the general case of M requests per N seconds

cuttle.yml

@@ -14,8 +14,9 @@ addr: :3128
 zones:
   - host: "*"  # Apply to requests forwarded to all domains.
     shared: true  # The rate limit is shared by all domains.
-    control: rps  # Use request-per-second rate limit control.
-    rate: 2  # At most 2 requests per second in the entire zone.
+    control: rpns  # Use request-per-second rate limit control.
+    rate: 1  # At most 1 requests per N second in the entire zone.
+    nseconds: 3 # N second = 3
 
 # Example - Only throttle *.github.com and no rate limit on other domains.
 #

cuttle/limitcontrol.go

@@ -186,3 +186,66 @@ func (c *RPMControl) Acquire() bool {
 
 	return true
 }
+
+// RPNSControl provides Rate requests per N seconds rate limit control.
+type RPNSControl struct {
+	// Label of this control.
+	Label string
+	// Rate holds the number of requests per N seconds.
+	Rate int
+    // Nseconds holds the number N of seconds within which limiting occurs
+    Nseconds int
+
+	pendingChan chan uint
+	readyChan   chan uint
+	seen        *list.List
+}
+
+// NewRPNSControl return a new RPNSControl with the given label and rate.
+func NewRPNSControl(label string, rate int, nseconds int) *RPNSControl {
+	return &RPNSControl{label, rate, nseconds, make(chan uint), make(chan uint), list.New()}
+}
+
+// Start running RPNSControl.
+// A goroutine is launched to govern the rate limit of Acquire().
+func (c *RPNSControl) Start() {
+	go func() {
+		log.Debugf("RPNSControl[%s]: Activated.", c.Label)
+
+		for {
+			<-c.pendingChan
+
+			log.Debugf("RPNSControl[%s]: Limited at %dreq/%ds.", c.Label, c.Rate, c.Nseconds)
+			if c.seen.Len() == c.Rate {
+				front := c.seen.Front()
+				nanoElapsed := time.Now().UnixNano() - front.Value.(int64)
+				milliElapsed := nanoElapsed / int64(time.Millisecond)
+				secondElapsed := milliElapsed / 1000
+				log.Debugf("RPNSControl[%s]: Elapsed %ds since first request.", c.Label, secondElapsed)
+
+				if waitTime := int64(c.Nseconds) - secondElapsed; waitTime > 0 {
+					log.Infof("RPNSControl[%s]: Waiting for %ds.", c.Label, waitTime)
+					time.Sleep(time.Duration(waitTime) * time.Second)
+				}
+
+				c.seen.Remove(front)
+			}
+			c.seen.PushBack(time.Now().UnixNano())
+
+			c.readyChan <- 1
+		}
+
+		log.Debugf("RPNSControl[%s]: Deactivated.", c.Label)
+	}()
+}
+
+// Acquire permission from RPNSControl.
+// Permission is granted at a rate of Rate requests per N seconds.
+func (c *RPNSControl) Acquire() bool {
+	log.Debugf("RPNSControl[%s]: Seeking permission.", c.Label)
+	c.pendingChan <- 1
+	<-c.readyChan
+	log.Debugf("RPNSControl[%s]: Granted permission.", c.Label)
+
+	return true
+}

cuttle/zone.go

@@ -29,14 +29,14 @@ type Zone struct {
 	Control string
 	// Rate specifies the rate of the rate limit controller.
 	Rate int
-
+    Nseconds int
 	controllers map[string]LimitController
 }
 
 // NewZone returns a new Zone given the configurations.
-func NewZone(host string, path string, limitby string, shared bool, control string, rate int) *Zone {
+func NewZone(host string, path string, limitby string, shared bool, control string, rate int, nseconds int) *Zone {
 	return &Zone{
-		host, path, limitby, shared, control, rate,
+		host, path, limitby, shared, control, rate, nseconds,
 		make(map[string]LimitController),
 	}
 }
@@ -102,6 +102,8 @@ func (z *Zone) GetController(host string, path string) LimitController {
 			controller = NewRPSControl(key, z.Rate)
 		case "rpm":
 			controller = NewRPMControl(key, z.Rate)
+        case "rpns":
+			controller = NewRPNSControl(key, z.Rate, z.Nseconds)
 		case "noop":
 			controller = NewNoopControl(key)
 		case "ban":

main.go

@@ -55,11 +55,15 @@ func main() {
 		if c.LimitBy == "" {
 			c.LimitBy = "host"
 		}
+
+        if c.Nseconds == 0 {
+            c.Nseconds = 1
+        }
 
-		log.Debugf("ZoneConfig: host - %s, path - %s, limitby - %s, shared - %t, control - %s, rate - %d",
-			c.Host, c.Path, c.LimitBy, c.Shared, c.Control, c.Rate)
+		log.Debugf("ZoneConfig: host - %s, path - %s, limitby - %s, shared - %t, control - %s, rate - %d, nseconds - %d",
+			c.Host, c.Path, c.LimitBy, c.Shared, c.Control, c.Rate, c.Nseconds)
 
-		zones[i] = *cuttle.NewZone(c.Host, c.Path, c.LimitBy, c.Shared, c.Control, c.Rate)
+		zones[i] = *cuttle.NewZone(c.Host, c.Path, c.LimitBy, c.Shared, c.Control, c.Rate, c.Nseconds)
 	}
 
 	// Config CA Cert.
@@ -130,10 +134,11 @@ type Config struct {
 }
 
 type ZoneConfig struct {
-	Host    string
-	Path    string // Optional, default "/"
-	LimitBy string // Optional, default "host"
-	Shared  bool   // Optional, default "false"
-	Control string
-	Rate    int
+	Host     string
+	Path     string // Optional, default "/"
+	LimitBy  string // Optional, default "host"
+	Shared   bool   // Optional, default "false"
+	Control  string
+	Rate     int
+    Nseconds int    // Optional, default "1"
 }