Implement pN load balancing strategy (#1188)

dnscrypt-proxy/config.go

@@ -363,17 +363,22 @@ func ConfigLoad(proxy *Proxy, flags *ConfigFlags) error {
 	switch strings.ToLower(config.LBStrategy) {
 	case "":
 		// default
-	case "p2":
-		lbStrategy = LBStrategyP2
 	case "ph":
 		lbStrategy = LBStrategyPH
 	case "fastest":
 	case "first":
-		lbStrategy = LBStrategyFirst
+		lbStrategy = LBStrategy(1)
 	case "random":
 		lbStrategy = LBStrategyRandom
+
 	default:
-		dlog.Warnf("Unknown load balancing strategy: [%s]", config.LBStrategy)
+		n, err := strconv.ParseUint(strings.TrimPrefix(config.LBStrategy, "p"), 10, 64)
+
+		if err == nil && n >= 1 {
+			lbStrategy = LBStrategy(n)
+		} else {
+			dlog.Warnf("Unknown load balancing strategy: [%s]", config.LBStrategy)
+		}
 	}
 	proxy.serversInfo.lbStrategy = lbStrategy
 	proxy.serversInfo.lbEstimator = config.LBEstimator

dnscrypt-proxy/example-dnscrypt-proxy.toml

@@ -126,6 +126,7 @@ keepalive = 30
 
 
 ## Load-balancing strategy: 'p2' (default), 'ph', 'first' or 'random'
+## Use pN where N is a positive number to choose between N first fastest servers.
 
 # lb_strategy = 'p2'
 

dnscrypt-proxy/serversInfo.go

@@ -65,14 +65,11 @@ type ServerInfo struct {
 type LBStrategy int
 
 const (
-	LBStrategyNone = LBStrategy(iota)
-	LBStrategyP2
-	LBStrategyPH
-	LBStrategyFirst
-	LBStrategyRandom
+	LBStrategyRandom = LBStrategy(0)
+	LBStrategyPH     = LBStrategy(-1)
 )
 
-const DefaultLBStrategy = LBStrategyP2
+const DefaultLBStrategy = LBStrategy(2)
 
 type ServersInfo struct {
 	sync.RWMutex
@@ -211,14 +208,12 @@ func (serversInfo *ServersInfo) getOne() *ServerInfo {
 	}
 	var candidate int
 	switch serversInfo.lbStrategy {
-	case LBStrategyFirst:
-		candidate = 0
-	case LBStrategyPH:
+	case -1: // First half
 		candidate = rand.Intn(Max(Min(serversCount, 2), serversCount/2))
-	case LBStrategyRandom:
+	case 0: // Random
 		candidate = rand.Intn(serversCount)
-	default:
-		candidate = rand.Intn(Min(serversCount, 2))
+	default: // First N
+		candidate = rand.Intn(int(serversInfo.lbStrategy)) % serversCount
 	}
 	serverInfo := serversInfo.inner[candidate]
 	dlog.Debugf("Using candidate [%s] RTT: %d", (*serverInfo).Name, int((*serverInfo).rtt.Value()))