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

Some changes will be necessary to integrate it into V2Ray

app/router/strategy_random.go

@@ -0,0 +1,38 @@
+package router
+
+import (
+	"github.com/v2fly/v2ray-core/v4/common/dice"
+	"github.com/v2fly/v2ray-core/v4/features/routing"
+)
+
+// RandomStrategy represents a random balancing strategy
+type RandomStrategy struct{}
+
+// GetInformation implements the routing.BalancingStrategy.
+func (s *RandomStrategy) GetInformation(tags []string) *routing.StrategyInfo {
+	items := make([]*routing.OutboundInfo, 0)
+	for _, tag := range tags {
+		items = append(items, &routing.OutboundInfo{Tag: tag})
+	}
+	return &routing.StrategyInfo{
+		Settings:    []string{"random"},
+		ValueTitles: nil,
+		Selects:     items,
+		Others:      nil,
+	}
+}
+
+// SelectAndPick implements the routing.BalancingStrategy.
+func (s *RandomStrategy) SelectAndPick(candidates []string) string {
+	return s.Pick(candidates)
+}
+
+// Pick implements the routing.BalancingStrategy.
+func (s *RandomStrategy) Pick(candidates []string) string {
+	count := len(candidates)
+	if count == 0 {
+		// goes to fallbackTag
+		return ""
+	}
+	return candidates[dice.Roll(count)]
+}