fetch health check nodes in time from the router by prefix ...

* Balancer & HealthCheck not hold adapter.Outbound, but only tags
* rename and unexport some structs and fields
* fix no check in the first rounds

balancer/balancer.go

@@ -6,6 +6,7 @@ import (
 	"sort"
 	"time"
 
+	"github.com/sagernet/sing-box/adapter"
 	"github.com/sagernet/sing-box/log"
 	"github.com/sagernet/sing-box/option"
 )
@@ -14,7 +15,7 @@ var _ Balancer = (*rttBasedBalancer)(nil)
 
 // Balancer is interface for load balancers
 type Balancer interface {
-	Pick() *Node
+	Pick() string
 }
 
 type rttBasedBalancer struct {
@@ -30,15 +31,14 @@ type rttFunc func(node *Node) time.Duration
 
 // newRTTBasedLoad creates a new rtt based load balancer
 func newRTTBasedBalancer(
-	nodes []*Node, logger log.ContextLogger,
+	router adapter.Router, logger log.ContextLogger,
 	options option.BalancerOutboundOptions,
 	rttFunc rttFunc,
 ) (Balancer, error) {
 	return &rttBasedBalancer{
-		nodes:       nodes,
 		rttFunc:     rttFunc,
 		options:     &options,
-		HealthCheck: NewHealthCheck(nodes, logger, &options.Check),
+		HealthCheck: NewHealthCheck(router, options.Outbounds, logger, &options.Check),
 		costs: NewWeightManager(
 			logger, options.Pick.Costs, 1,
 			func(value, cost float64) float64 {
@@ -49,28 +49,33 @@ func newRTTBasedBalancer(
 }
 
 // Select selects qualified nodes
-func (s *rttBasedBalancer) Pick() *Node {
+func (s *rttBasedBalancer) Pick() string {
 	nodes := s.HealthCheck.NodesByCategory()
 	var candidates []*Node
 	if len(nodes.Qualified) > 0 {
 		candidates = nodes.Qualified
 		for _, node := range candidates {
-			node.Weighted = time.Duration(s.costs.Apply(node.Outbound.Tag(), float64(s.rttFunc(node))))
+			node.Weighted = time.Duration(s.costs.Apply(node.Tag, float64(s.rttFunc(node))))
 		}
 		sortNodes(candidates)
 	} else {
 		candidates = nodes.Untested
 		shuffleNodes(candidates)
 	}
-	selects := selectNodes(
-		candidates, s.logger,
-		int(s.options.Pick.Expected), s.options.Pick.Baselines,
-	)
+	selects := selectNodes(candidates, int(s.options.Pick.Expected), s.options.Pick.Baselines)
 	count := len(selects)
 	if count == 0 {
-		return nil
+		return ""
 	}
-	return selects[rand.Intn(count)]
+	picked := selects[rand.Intn(count)]
+	s.logger.Debug(
+		"pick [", picked.Tag, "]",
+		" +W=", picked.Weighted,
+		" STD=", picked.Deviation,
+		" AVG=", picked.Average,
+		" Fail=", picked.Fail, "/", picked.All,
+	)
+	return picked.Tag
 }
 
 func sortNodes(nodes []*Node) {

balancer/balancer_select.go

@@ -3,7 +3,6 @@ package balancer
 import (
 	"time"
 
-	"github.com/sagernet/sing-box/log"
 	"github.com/sagernet/sing-box/option"
 )
 
@@ -23,7 +22,7 @@ import (
 // 3. Speed priority: Baselines + `Expected Count <= 0`.
 // go through all baselines until find selects, if not, select none. Used in combination
 // with 'balancer.fallbackTag', it means: selects qualified nodes or use the fallback.
-func selectNodes(nodes []*Node, logger log.Logger, expected int, baselines []option.Duration) []*Node {
+func selectNodes(nodes []*Node, expected int, baselines []option.Duration) []*Node {
 	if len(nodes) == 0 {
 		// s.logger.Debug("no qualified nodes")
 		return nil
@@ -53,9 +52,6 @@ func selectNodes(nodes []*Node, logger log.Logger, expected int, baselines []opt
 		}
 		// don't continue if find expected selects
 		if count >= expected2 {
-			if logger != nil {
-				logger.Debug("applied baseline: ", baseline)
-			}
 			break
 		}
 	}

balancer/balancer_select_test.go

@@ -8,12 +8,12 @@ import (
 
 func TestSelectNodes(t *testing.T) {
 	nodes := []*Node{
-		{HealthCheckStats: HealthCheckStats{Weighted: 50}},
-		{HealthCheckStats: HealthCheckStats{Weighted: 70}},
-		{HealthCheckStats: HealthCheckStats{Weighted: 100}},
-		{HealthCheckStats: HealthCheckStats{Weighted: 110}},
-		{HealthCheckStats: HealthCheckStats{Weighted: 120}},
-		{HealthCheckStats: HealthCheckStats{Weighted: 150}},
+		{RTTStats: RTTStats{Weighted: 50}},
+		{RTTStats: RTTStats{Weighted: 70}},
+		{RTTStats: RTTStats{Weighted: 100}},
+		{RTTStats: RTTStats{Weighted: 110}},
+		{RTTStats: RTTStats{Weighted: 120}},
+		{RTTStats: RTTStats{Weighted: 150}},
 	}
 	tests := []struct {
 		expected  int
@@ -31,7 +31,7 @@ func TestSelectNodes(t *testing.T) {
 	}
 	for _, tt := range tests {
 		t.Run("", func(t *testing.T) {
-			if got := selectNodes(nodes, nil, tt.expected, tt.baselines); len(got) != tt.want {
+			if got := selectNodes(nodes, tt.expected, tt.baselines); len(got) != tt.want {
 				t.Errorf("selectNodes() = %v, want %v", len(got), tt.want)
 			}
 		})

balancer/healthcheck.go

@@ -6,6 +6,7 @@ import (
 	"sync"
 	"time"
 
+	"github.com/sagernet/sing-box/adapter"
 	"github.com/sagernet/sing-box/log"
 	"github.com/sagernet/sing-box/option"
 	E "github.com/sagernet/sing/common/exceptions"
@@ -16,15 +17,16 @@ type HealthCheck struct {
 	sync.Mutex
 
 	ticker *time.Ticker
-	nodes  []*Node
+	router adapter.Router
+	tags   []string
 	logger log.Logger
 
 	options *option.HealthCheckSettings
-	Results map[string]*HealthCheckRTTS
+	results map[string]*rttStorage
 }
 
 // NewHealthCheck creates a new HealthPing with settings
-func NewHealthCheck(outbounds []*Node, logger log.Logger, config *option.HealthCheckSettings) *HealthCheck {
+func NewHealthCheck(router adapter.Router, tags []string, logger log.Logger, config *option.HealthCheckSettings) *HealthCheck {
 	if config == nil {
 		config = &option.HealthCheckSettings{}
 	}
@@ -46,29 +48,33 @@ func NewHealthCheck(outbounds []*Node, logger log.Logger, config *option.HealthC
 		config.Timeout = option.Duration(5 * time.Second)
 	}
 	return &HealthCheck{
-		nodes:   outbounds,
+		router:  router,
+		tags:    tags,
 		options: config,
-		Results: nil,
+		results: make(map[string]*rttStorage),
 		logger:  logger,
 	}
 }
 
 // Start starts the health check service
 func (h *HealthCheck) Start() error {
+	h.Lock()
+	defer h.Unlock()
 	if h.ticker != nil {
 		return nil
 	}
 	interval := time.Duration(h.options.Interval) * time.Duration(h.options.SamplingCount)
 	ticker := time.NewTicker(interval)
 	h.ticker = ticker
+	// one time instant check
+	h.Check()
 	go func() {
-		h.doCheck(0, 1)
 		for {
+			h.doCheck(interval, h.options.SamplingCount)
 			_, ok := <-ticker.C
 			if !ok {
 				break
 			}
-			h.doCheck(interval, h.options.SamplingCount)
 		}
 	}()
 	return nil
@@ -76,17 +82,17 @@ func (h *HealthCheck) Start() error {
 
 // Stop stops the health check service
 func (h *HealthCheck) Stop() {
-	h.ticker.Stop()
-	h.ticker = nil
+	h.Lock()
+	defer h.Unlock()
+	if h.ticker != nil {
+		h.ticker.Stop()
+		h.ticker = nil
+	}
 }
 
 // Check does a one time health check
-func (h *HealthCheck) Check() error {
-	if len(h.nodes) == 0 {
-		return nil
-	}
-	h.doCheck(0, 1)
-	return nil
+func (h *HealthCheck) Check() {
+	go h.doCheck(0, 1)
 }
 
 type rtt struct {
@@ -97,14 +103,15 @@ type rtt struct {
 // doCheck performs the 'rounds' amount checks in given 'duration'. You should make
 // sure all tags are valid for current balancer
 func (h *HealthCheck) doCheck(duration time.Duration, rounds int) {
-	count := len(h.nodes) * rounds
+	nodes := h.refreshNodes()
+	count := len(nodes) * rounds
 	if count == 0 {
 		return
 	}
 	ch := make(chan *rtt, count)
 	// rtts := make(map[string][]time.Duration)
-	for _, node := range h.nodes {
-		tag, detour := node.Outbound.Tag(), node.Outbound
+	for _, node := range nodes {
+		tag, detour := node.Tag(), node
 		client := newPingClient(
 			detour,
 			h.options.Destination,
@@ -160,18 +167,10 @@ func (h *HealthCheck) doCheck(duration time.Duration, rounds int) {
 func (h *HealthCheck) PutResult(tag string, rtt time.Duration) {
 	h.Lock()
 	defer h.Unlock()
-	if h.Results == nil {
-		h.Results = make(map[string]*HealthCheckRTTS)
-	}
-	r, ok := h.Results[tag]
+	r, ok := h.results[tag]
 	if !ok {
-		// validity is 2 times to sampling period, since the check are
-		// distributed in the time line randomly, in extreme cases,
-		// previous checks are distributed on the left, and latters
-		// on the right
-		validity := time.Duration(h.options.Interval) * time.Duration(h.options.SamplingCount) * 2
-		r = NewHealthPingResult(h.options.SamplingCount, validity)
-		h.Results[tag] = r
+		// the result may come after the node is removed
+		return
 	}
 	r.Put(rtt)
 }

balancer/healthcheck_nodes.go

@@ -1,6 +1,11 @@
 package balancer
 
-import "time"
+import (
+	"strings"
+	"time"
+
+	"github.com/sagernet/sing-box/adapter"
+)
 
 // CategorizedNodes holds the categorized nodes
 type CategorizedNodes struct {
@@ -12,28 +17,24 @@ type CategorizedNodes struct {
 func (h *HealthCheck) NodesByCategory() *CategorizedNodes {
 	h.Lock()
 	defer h.Unlock()
-	if h == nil || h.Results == nil {
-		return &CategorizedNodes{
-			Untested: h.nodes,
-		}
+	if h == nil || len(h.results) == 0 {
+		return &CategorizedNodes{}
 	}
 	nodes := &CategorizedNodes{
-		Qualified:   make([]*Node, 0, len(h.nodes)),
-		Unqualified: make([]*Node, 0, len(h.nodes)),
-		Failed:      make([]*Node, 0, len(h.nodes)),
-		Untested:    make([]*Node, 0, len(h.nodes)),
+		Qualified:   make([]*Node, 0, len(h.results)),
+		Unqualified: make([]*Node, 0, len(h.results)),
+		Failed:      make([]*Node, 0, len(h.results)),
+		Untested:    make([]*Node, 0, len(h.results)),
 	}
-	for _, node := range h.nodes {
-		r, ok := h.Results[node.Outbound.Tag()]
-		if !ok {
-			node.HealthCheckStats = healthPingStatsUntested
-			continue
+	for tag, result := range h.results {
+		node := &Node{
+			Tag:      tag,
+			RTTStats: result.Get(),
 		}
-		node.HealthCheckStats = r.Get()
 		switch {
-		case node.HealthCheckStats.All == 0:
+		case node.RTTStats.All == 0:
 			nodes.Untested = append(nodes.Untested, node)
-		case node.HealthCheckStats.All == node.HealthCheckStats.Fail,
+		case node.RTTStats.All == node.RTTStats.Fail,
 			float64(node.Fail)/float64(node.All) > float64(h.options.Tolerance):
 			nodes.Failed = append(nodes.Failed, node)
 		case h.options.MaxRTT > 0 && node.Average > time.Duration(h.options.MaxRTT):
@@ -44,3 +45,49 @@ func (h *HealthCheck) NodesByCategory() *CategorizedNodes {
 	}
 	return nodes
 }
+
+// CoveredOutbounds returns the outbounds that should covered by health check
+func CoveredOutbounds(router adapter.Router, tags []string) []adapter.Outbound {
+	outbounds := router.Outbounds()
+	nodes := make([]adapter.Outbound, 0, len(outbounds))
+	for _, outbound := range outbounds {
+		for _, prefix := range tags {
+			tag := outbound.Tag()
+			if strings.HasPrefix(tag, prefix) {
+				nodes = append(nodes, outbound)
+			}
+		}
+	}
+	return nodes
+}
+
+// refreshNodes matches nodes from router by tag prefix, and refreshes the health check results
+func (h *HealthCheck) refreshNodes() []adapter.Outbound {
+	h.Lock()
+	defer h.Unlock()
+
+	nodes := CoveredOutbounds(h.router, h.tags)
+	tags := make(map[string]struct{})
+	for _, node := range nodes {
+		tag := node.Tag()
+		tags[tag] = struct{}{}
+		// make it known to the health check results
+		r, ok := h.results[tag]
+		if !ok {
+			// validity is 2 times to sampling period, since the check are
+			// distributed in the time line randomly, in extreme cases,
+			// previous checks are distributed on the left, and latters
+			// on the right
+			validity := time.Duration(h.options.Interval) * time.Duration(h.options.SamplingCount) * 2
+			r = newRTTStorage(h.options.SamplingCount, validity)
+			h.results[tag] = r
+		}
+	}
+	// remove unused rttStorage
+	for tag := range h.results {
+		if _, ok := tags[tag]; !ok {
+			delete(h.results, tag)
+		}
+	}
+	return nodes
+}

balancer/leastload.go

@@ -3,17 +3,18 @@ package balancer
 import (
 	"time"
 
+	"github.com/sagernet/sing-box/adapter"
 	"github.com/sagernet/sing-box/log"
 	"github.com/sagernet/sing-box/option"
 )
 
 // NewLeastLoad creates a new LeastLoad outbound
 func NewLeastLoad(
-	nodes []*Node, logger log.ContextLogger,
+	router adapter.Router, logger log.ContextLogger,
 	options option.BalancerOutboundOptions,
 ) (Balancer, error) {
 	return newRTTBasedBalancer(
-		nodes, logger, options,
+		router, logger, options,
 		func(node *Node) time.Duration {
 			return node.Deviation
 		},

balancer/leastping.go

@@ -3,17 +3,18 @@ package balancer
 import (
 	"time"
 
+	"github.com/sagernet/sing-box/adapter"
 	"github.com/sagernet/sing-box/log"
 	"github.com/sagernet/sing-box/option"
 )
 
 // NewLeastPing creates a new LeastPing outbound
 func NewLeastPing(
-	nodes []*Node, logger log.ContextLogger,
+	router adapter.Router, logger log.ContextLogger,
 	options option.BalancerOutboundOptions,
 ) (Balancer, error) {
 	return newRTTBasedBalancer(
-		nodes, logger, options,
+		router, logger, options,
 		func(node *Node) time.Duration {
 			return node.Average
 		},

balancer/node.go

@@ -1,10 +1,6 @@
 package balancer
 
-import (
-	"github.com/sagernet/sing-box/adapter"
-)
-
-var healthPingStatsUntested = HealthCheckStats{
+var healthPingStatsUntested = RTTStats{
 	All:       0,
 	Fail:      0,
 	Deviation: rttUntested,
@@ -15,14 +11,6 @@ var healthPingStatsUntested = HealthCheckStats{
 
 // Node is a banalcer node with health check result
 type Node struct {
-	Outbound adapter.Outbound
-	HealthCheckStats
-}
-
-// NewNode creates a new balancer node from outbound
-func NewNode(outbound adapter.Outbound) *Node {
-	return &Node{
-		Outbound:         outbound,
-		HealthCheckStats: healthPingStatsUntested,
-	}
+	Tag string
+	RTTStats
 }

balancer/rtt_storage.go

@@ -11,8 +11,8 @@ const (
 	rttUnqualified
 )
 
-// HealthCheckStats is the statistics of HealthPingRTTS
-type HealthCheckStats struct {
+// RTTStats is the statistics of health check RTTs
+type RTTStats struct {
 	All       int
 	Fail      int
 	Deviation time.Duration
@@ -23,15 +23,15 @@ type HealthCheckStats struct {
 	Weighted time.Duration
 }
 
-// HealthCheckRTTS holds ping rtts for health Checker
-type HealthCheckRTTS struct {
+// rttStorage holds ping rtts for health Checker
+type rttStorage struct {
 	idx      int
 	cap      int
 	validity time.Duration
 	rtts     []*pingRTT
 
 	lastUpdateAt time.Time
-	stats        *HealthCheckStats
+	stats        *RTTStats
 }
 
 type pingRTT struct {
@@ -39,25 +39,25 @@ type pingRTT struct {
 	value time.Duration
 }
 
-// NewHealthPingResult returns a *HealthPingResult with specified capacity
-func NewHealthPingResult(cap int, validity time.Duration) *HealthCheckRTTS {
-	return &HealthCheckRTTS{cap: cap, validity: validity}
+// newRTTStorage returns a *HealthPingResult with specified capacity
+func newRTTStorage(cap int, validity time.Duration) *rttStorage {
+	return &rttStorage{cap: cap, validity: validity}
 }
 
 // Get gets statistics of the HealthPingRTTS
-func (h *HealthCheckRTTS) Get() HealthCheckStats {
+func (h *rttStorage) Get() RTTStats {
 	return h.getStatistics()
 }
 
 // GetWithCache get statistics and write cache for next call
 // Make sure use Mutex.Lock() before calling it, RWMutex.RLock()
 // is not an option since it writes cache
-func (h *HealthCheckRTTS) GetWithCache() HealthCheckStats {
+func (h *rttStorage) GetWithCache() RTTStats {
 	lastPutAt := h.rtts[h.idx].time
 	now := time.Now()
 	if h.stats == nil || h.lastUpdateAt.Before(lastPutAt) || h.findOutdated(now) >= 0 {
 		if h.stats == nil {
-			h.stats = &HealthCheckStats{}
+			h.stats = &RTTStats{}
 		}
 		*h.stats = h.getStatistics()
 		h.lastUpdateAt = now
@@ -66,7 +66,7 @@ func (h *HealthCheckRTTS) GetWithCache() HealthCheckStats {
 }
 
 // Put puts a new rtt to the HealthPingResult
-func (h *HealthCheckRTTS) Put(d time.Duration) {
+func (h *rttStorage) Put(d time.Duration) {
 	if h.rtts == nil {
 		h.rtts = make([]*pingRTT, h.cap)
 		for i := 0; i < h.cap; i++ {
@@ -80,7 +80,7 @@ func (h *HealthCheckRTTS) Put(d time.Duration) {
 	h.rtts[h.idx].value = d
 }
 
-func (h *HealthCheckRTTS) calcIndex(step int) int {
+func (h *rttStorage) calcIndex(step int) int {
 	idx := h.idx
 	idx += step
 	if idx >= h.cap {
@@ -89,8 +89,8 @@ func (h *HealthCheckRTTS) calcIndex(step int) int {
 	return idx
 }
 
-func (h *HealthCheckRTTS) getStatistics() HealthCheckStats {
-	stats := HealthCheckStats{}
+func (h *rttStorage) getStatistics() RTTStats {
+	stats := RTTStats{}
 	stats.Fail = 0
 	stats.Max = 0
 	stats.Min = rttFailed
@@ -125,7 +125,7 @@ func (h *HealthCheckRTTS) getStatistics() HealthCheckStats {
 	case stats.All == 0:
 		return healthPingStatsUntested
 	case stats.Fail == stats.All:
-		return HealthCheckStats{
+		return RTTStats{
 			All:       stats.All,
 			Fail:      stats.Fail,
 			Deviation: rttFailed,
@@ -151,7 +151,7 @@ func (h *HealthCheckRTTS) getStatistics() HealthCheckStats {
 	return stats
 }
 
-func (h *HealthCheckRTTS) findOutdated(now time.Time) int {
+func (h *rttStorage) findOutdated(now time.Time) int {
 	for i := h.cap - 1; i < 2*h.cap; i++ {
 		// from oldest to latest
 		idx := h.calcIndex(i)

balancer/rtt_storage_test.go

@@ -1,22 +1,20 @@
-package balancer_test
+package balancer
 
 import (
 	"math"
 	"reflect"
 	"testing"
 	"time"
-
-	"github.com/sagernet/sing-box/balancer"
 )
 
-func TestHealthPingResults(t *testing.T) {
+func TestRTTStorage(t *testing.T) {
 	rtts := []int64{60, 140, 60, 140, 60, 60, 140, 60, 140}
-	hr := balancer.NewHealthPingResult(4, time.Hour)
+	hr := newRTTStorage(4, time.Hour)
 	for _, rtt := range rtts {
 		hr.Put(time.Duration(rtt))
 	}
 	rttFailed := time.Duration(math.MaxInt64)
-	expected := &balancer.HealthCheckStats{
+	expected := &RTTStats{
 		All:       4,
 		Fail:      0,
 		Deviation: 40,
@@ -37,7 +35,7 @@ func TestHealthPingResults(t *testing.T) {
 	}
 	hr.Put(rttFailed)
 	hr.Put(rttFailed)
-	expected = &balancer.HealthCheckStats{
+	expected = &RTTStats{
 		All:       4,
 		Fail:      4,
 		Deviation: 0,
@@ -53,7 +51,7 @@ func TestHealthPingResults(t *testing.T) {
 
 func TestHealthPingResultsIgnoreOutdated(t *testing.T) {
 	rtts := []int64{60, 140, 60, 140}
-	hr := balancer.NewHealthPingResult(4, time.Duration(10)*time.Millisecond)
+	hr := newRTTStorage(4, time.Duration(10)*time.Millisecond)
 	for i, rtt := range rtts {
 		if i == 2 {
 			// wait for previous 2 outdated
@@ -62,7 +60,7 @@ func TestHealthPingResultsIgnoreOutdated(t *testing.T) {
 		hr.Put(time.Duration(rtt))
 	}
 	hr.Get()
-	expected := &balancer.HealthCheckStats{
+	expected := &RTTStats{
 		All:       2,
 		Fail:      0,
 		Deviation: 40,
@@ -76,7 +74,7 @@ func TestHealthPingResultsIgnoreOutdated(t *testing.T) {
 	}
 	// wait for all outdated
 	time.Sleep(time.Duration(10) * time.Millisecond)
-	expected = &balancer.HealthCheckStats{
+	expected = &RTTStats{
 		All:       0,
 		Fail:      0,
 		Deviation: 0,
@@ -90,7 +88,7 @@ func TestHealthPingResultsIgnoreOutdated(t *testing.T) {
 	}
 
 	hr.Put(time.Duration(60))
-	expected = &balancer.HealthCheckStats{
+	expected = &RTTStats{
 		All:  1,
 		Fail: 0,
 		// 1 sample, std=0.5rtt

outbound/balancer.go

@@ -27,7 +27,6 @@ type Balancer struct {
 	fallbackTag string
 
 	balancer.Balancer
-	nodes    []*balancer.Node
 	fallback adapter.Outbound
 }
 
@@ -106,13 +105,6 @@ func (s *Balancer) initialize() error {
 		return E.New("fallback outbound not found: ", s.fallbackTag)
 	}
 	s.fallback = outbound
-	for i, tag := range s.tags {
-		outbound, loaded := s.router.Outbound(tag)
-		if !loaded {
-			return E.New("outbound ", i, " not found: ", tag)
-		}
-		s.nodes = append(s.nodes, balancer.NewNode(outbound))
-	}
 	return nil
 }
 
@@ -128,19 +120,34 @@ func (s *Balancer) setBalancer(b balancer.Balancer) error {
 }
 
 func (s *Balancer) pick() adapter.Outbound {
-	if s.Balancer != nil {
-		selected := s.Balancer.Pick()
-		if selected == nil {
-			return s.fallback
-		}
-		return selected.Outbound
-	}
-	// not started
-	count := len(s.nodes)
-	if count == 0 {
-		// goes to fallback
+	tag := s.pickTag()
+	if tag == "" {
 		return s.fallback
 	}
-	picked := s.nodes[rand.Intn(count)]
-	return picked.Outbound
+	outbound, ok := s.router.Outbound(tag)
+	if !ok {
+		return s.fallback
+	}
+	return outbound
+}
+
+func (s *Balancer) pickTag() string {
+	if s.Balancer == nil {
+		// not started yet, pick a random one
+		return s.randomTag()
+	}
+	tag := s.Balancer.Pick()
+	if tag == "" {
+		return ""
+	}
+	return tag
+}
+
+func (s *Balancer) randomTag() string {
+	nodes := balancer.CoveredOutbounds(s.router, s.tags)
+	count := len(nodes)
+	if count == 0 {
+		return ""
+	}
+	return s.tags[rand.Intn(count)]
 }

outbound/leastload.go

@@ -6,7 +6,6 @@ import (
 	C "github.com/sagernet/sing-box/constant"
 	"github.com/sagernet/sing-box/log"
 	"github.com/sagernet/sing-box/option"
-	E "github.com/sagernet/sing/common/exceptions"
 )
 
 var (
@@ -23,9 +22,6 @@ type LeastLoad struct {
 
 // NewLeastLoad creates a new LeastLoad outbound
 func NewLeastLoad(router adapter.Router, logger log.ContextLogger, tag string, options option.BalancerOutboundOptions) (*LeastLoad, error) {
-	if len(options.Outbounds) == 0 {
-		return nil, E.New("missing tags")
-	}
 	return &LeastLoad{
 		Balancer: NewBalancer(
 			C.TypeLeastLoad, router, logger, tag,
@@ -41,7 +37,7 @@ func (s *LeastLoad) Start() error {
 	if err != nil {
 		return err
 	}
-	b, err := balancer.NewLeastLoad(s.nodes, s.logger, s.options)
+	b, err := balancer.NewLeastLoad(s.router, s.logger, s.options)
 	if err != nil {
 		return err
 	}

outbound/leastping.go

@@ -6,7 +6,6 @@ import (
 	C "github.com/sagernet/sing-box/constant"
 	"github.com/sagernet/sing-box/log"
 	"github.com/sagernet/sing-box/option"
-	E "github.com/sagernet/sing/common/exceptions"
 )
 
 var (
@@ -23,9 +22,6 @@ type LeastPing struct {
 
 // NewLeastPing creates a new LeastPing outbound
 func NewLeastPing(router adapter.Router, logger log.ContextLogger, tag string, options option.BalancerOutboundOptions) (*LeastPing, error) {
-	if len(options.Outbounds) == 0 {
-		return nil, E.New("missing tags")
-	}
 	return &LeastPing{
 		Balancer: NewBalancer(
 			C.TypeLeastPing, router, logger, tag,
@@ -41,7 +37,7 @@ func (s *LeastPing) Start() error {
 	if err != nil {
 		return err
 	}
-	b, err := balancer.NewLeastPing(s.nodes, s.logger, s.options)
+	b, err := balancer.NewLeastPing(s.router, s.logger, s.options)
 	if err != nil {
 		return err
 	}