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

Some changes will be necessary to integrate it into V2Ray

app/router/balancing_override.go

@@ -0,0 +1,83 @@
+package router
+
+import (
+	sync "sync"
+	"time"
+
+	"github.com/v2fly/v2ray-core/v4/features/outbound"
+)
+
+func (b *Balancer) overrideSelecting(selects []string, validity time.Duration) error {
+	if validity <= 0 {
+		b.override.Clear()
+		return nil
+	}
+	hs, ok := b.ohm.(outbound.HandlerSelector)
+	if !ok {
+		return newError("outbound.Manager is not a HandlerSelector")
+	}
+	tags := hs.Select(selects)
+	if len(tags) == 0 {
+		return newError("no outbound selected")
+	}
+	b.override.Put(tags, time.Now().Add(validity))
+	return nil
+}
+
+// OverrideSelecting implements routing.BalancingOverrider
+func (r *Router) OverrideSelecting(balancer string, selects []string, validity time.Duration) error {
+	var b *Balancer
+	for tag, bl := range r.balancers {
+		if tag == balancer {
+			b = bl
+			break
+		}
+	}
+	if b == nil {
+		return newError("balancer '", balancer, "' not found")
+	}
+	err := b.overrideSelecting(selects, validity)
+	if err != nil {
+		return err
+	}
+	return nil
+}
+
+type overriddenSettings struct {
+	selects []string
+	until   time.Time
+}
+
+type overridden struct {
+	access   sync.RWMutex
+	settings overriddenSettings
+}
+
+// Get gets the overridden settings
+func (o *overridden) Get() *overriddenSettings {
+	o.access.RLock()
+	defer o.access.RUnlock()
+	if len(o.settings.selects) == 0 || time.Now().After(o.settings.until) {
+		return nil
+	}
+	return &overriddenSettings{
+		selects: o.settings.selects,
+		until:   o.settings.until,
+	}
+}
+
+// Put updates the overridden settings
+func (o *overridden) Put(selects []string, until time.Time) {
+	o.access.Lock()
+	defer o.access.Unlock()
+	o.settings.selects = selects
+	o.settings.until = until
+}
+
+// Clear clears the overridden settings
+func (o *overridden) Clear() {
+	o.access.Lock()
+	defer o.access.Unlock()
+	o.settings.selects = nil
+	o.settings.until = time.Time{}
+}