support principle target output

app/router/strategy_leastload.go

@@ -22,6 +22,15 @@ type LeastLoadStrategy struct {
 	ctx context.Context
 }
 
+func (l *LeastLoadStrategy) GetPrincipleTarget(strings []string) []string {
+	var ret []string
+	nodes := l.pickOutbounds(strings)
+	for _, v := range nodes {
+		ret = append(ret, v.Tag)
+	}
+	return ret
+}
+
 // NewLeastLoadStrategy creates a new LeastLoadStrategy with settings
 func NewLeastLoadStrategy(settings *StrategyLeastLoadConfig) *LeastLoadStrategy {
 	return &LeastLoadStrategy{
@@ -56,8 +65,7 @@ func (l *LeastLoadStrategy) InjectContext(ctx context.Context) {
 }
 
 func (s *LeastLoadStrategy) PickOutbound(candidates []string) string {
-	qualified := s.getNodes(candidates, time.Duration(s.settings.MaxRTT))
-	selects := s.selectLeastLoad(qualified)
+	selects := s.pickOutbounds(candidates)
 	count := len(selects)
 	if count == 0 {
 		// goes to fallbackTag
@@ -66,6 +74,12 @@ func (s *LeastLoadStrategy) PickOutbound(candidates []string) string {
 	return selects[dice.Roll(count)].Tag
 }
 
+func (s *LeastLoadStrategy) pickOutbounds(candidates []string) []*node {
+	qualified := s.getNodes(candidates, time.Duration(s.settings.MaxRTT))
+	selects := s.selectLeastLoad(qualified)
+	return selects
+}
+
 // selectLeastLoad selects nodes according to Baselines and Expected Count.
 //
 // The strategy always improves network response speed, not matter which mode below is configured.

app/router/strategy_leastping.go

@@ -17,6 +17,10 @@ type LeastPingStrategy struct {
 	observatory extension.Observatory
 }
 
+func (l *LeastPingStrategy) GetPrincipleTarget(strings []string) []string {
+	return []string{l.PickOutbound(strings)}
+}
+
 func (l *LeastPingStrategy) InjectContext(ctx context.Context) {
 	l.ctx = ctx
 }

app/router/strategy_random.go

@@ -7,6 +7,10 @@ import (
 // RandomStrategy represents a random balancing strategy
 type RandomStrategy struct{}
 
+func (s *RandomStrategy) GetPrincipleTarget(strings []string) []string {
+	return strings
+}
+
 func (s *RandomStrategy) PickOutbound(candidates []string) string {
 	count := len(candidates)
 	if count == 0 {