v5: Health Check & LeastLoad Strategy (rebased from 2c5a714903)

Some changes will be necessary to integrate it into V2Ray

app/router/balancing.go

@@ -5,8 +5,8 @@ package router
 
 import (
 	"context"
+	"github.com/v2fly/v2ray-core/v4/features/routing"
 
-	"github.com/v2fly/v2ray-core/v4/common/dice"
 	"github.com/v2fly/v2ray-core/v4/features/extension"
 	"github.com/v2fly/v2ray-core/v4/features/outbound"
 )
@@ -15,34 +15,37 @@ type BalancingStrategy interface {
 	PickOutbound([]string) string
 }
 
-type RandomStrategy struct{}
-
-func (s *RandomStrategy) PickOutbound(tags []string) string {
-	n := len(tags)
-	if n == 0 {
-		panic("0 tags")
-	}
-
-	return tags[dice.Roll(n)]
-}
-
 type Balancer struct {
-	selectors []string
-	strategy  BalancingStrategy
-	ohm       outbound.Manager
+	selectors   []string
+	strategy    routing.BalancingStrategy
+	ohm         outbound.Manager
+	fallbackTag string
+
+	override overridden
 }
 
+// PickOutbound picks the tag of a outbound
 func (b *Balancer) PickOutbound() (string, error) {
-	hs, ok := b.ohm.(outbound.HandlerSelector)
-	if !ok {
-		return "", newError("outbound.Manager is not a HandlerSelector")
+	candidates, err := b.SelectOutbounds()
+	if err != nil {
+		if b.fallbackTag != "" {
+			newError("fallback to [", b.fallbackTag, "], due to error: ", err).AtInfo().WriteToLog()
+			return b.fallbackTag, nil
+		}
+		return "", err
 	}
-	tags := hs.Select(b.selectors)
-	if len(tags) == 0 {
-		return "", newError("no available outbounds selected")
+	var tag string
+	if o := b.override.Get(); o != nil {
+		tag = b.strategy.Pick(o.selects)
+	} else {
+		tag = b.strategy.SelectAndPick(candidates)
 	}
-	tag := b.strategy.PickOutbound(tags)
 	if tag == "" {
+		if b.fallbackTag != "" {
+			newError("fallback to [", b.fallbackTag, "], due to empty tag returned").AtInfo().WriteToLog()
+			return b.fallbackTag, nil
+		}
+		// will use default handler
 		return "", newError("balancing strategy returns empty tag")
 	}
 	return tag, nil
@@ -53,3 +56,13 @@ func (b *Balancer) InjectContext(ctx context.Context) {
 		contextReceiver.InjectContext(ctx)
 	}
 }
+
+// SelectOutbounds select outbounds with selectors of the Balancer
+func (b *Balancer) SelectOutbounds() ([]string, error) {
+	hs, ok := b.ohm.(outbound.HandlerSelector)
+	if !ok {
+		return nil, newError("outbound.Manager is not a HandlerSelector")
+	}
+	tags := hs.Select(b.selectors)
+	return tags, nil
+}