add weight base strategy

rule/forward.go

@@ -27,6 +27,7 @@ type Forwarder struct {
 	latency     int64
 	intface     string // local interface or ip address
 	handlers    []StatusHandler
+	weight      int64
 }
 
 // ForwarderFromURL parses `forward=` command value and returns a new forwarder.
@@ -97,6 +98,17 @@ func (f *Forwarder) parseOption(option string) error {
 	}
 	f.SetPriority(uint32(priority))
 
+	var weight int64
+	w := query.Get("weight")
+	if w != "" {
+		weight, err = strconv.ParseInt(w, 10, 32)
+		if err == nil && weight > 0 {
+			f.SetWeight(weight)
+		} else if weight < 0 {
+			log.F("weight should be more than 0, ignore weight value")
+		}
+	}
+
 	f.intface = query.Get("interface")
 
 	return err
@@ -204,3 +216,11 @@ func (f *Forwarder) Latency() int64 {
 func (f *Forwarder) SetLatency(l int64) {
 	atomic.StoreInt64(&f.latency, l)
 }
+func (f *Forwarder) Weight() int64 {
+	return f.weight
+}
+
+// SetWeight sets the weight of forwarder.
+func (f *Forwarder) SetWeight(w int64) {
+	f.weight = w
+}

rule/group.go

@@ -3,6 +3,7 @@ package rule
 import (
 	"errors"
 	"hash/fnv"
+	"math/rand"
 	"net"
 	"net/url"
 	"path/filepath"
@@ -33,6 +34,7 @@ type FwdrGroup struct {
 	index           uint32
 	priority        uint32
 	next            func(addr string) *Forwarder
+	randomGenerator *rand.Rand
 }
 
 // NewFwdrGroup returns a new forward group.
@@ -88,6 +90,10 @@ func newFwdrGroup(name string, fwdrs []*Forwarder, c *Strategy) *FwdrGroup {
 		case "dh":
 			p.next = p.scheduleDH
 			log.F("[strategy] %s: %d forwarders forward in destination hashing mode.", name, count)
+		case "wb":
+			p.next = p.scheduleWB
+			p.randomGenerator = rand.New(rand.NewSource(time.Now().UnixNano()))
+			log.F("[strategy] %s: %d forwarders forward in Weight base mode.", name, count)
 		default:
 			p.next = p.scheduleRR
 			log.F("[strategy] %s: not supported forward mode '%s', use round robin mode for %d forwarders.", name, c.Strategy, count)
@@ -316,3 +322,30 @@ func (p *FwdrGroup) scheduleDH(dstAddr string) *Forwarder {
 	fnv1a.Write([]byte(dstAddr))
 	return p.avail[fnv1a.Sum32()%uint32(len(p.avail))]
 }
+
+// Weight base
+func (p *FwdrGroup) scheduleWB(dstAddr string) *Forwarder {
+	totalWeight := int64(0)
+	for _, f := range p.avail {
+		totalWeight += f.Weight()
+	}
+	if totalWeight <= 0 {
+		log.F("total weight is zero switch to rr mode")
+		return p.scheduleRR(dstAddr)
+	}
+	r := p.randomGenerator.Int63n(totalWeight)
+	var sum int64 = 0
+	for _, f := range p.avail {
+		weight := f.Weight()
+		if weight == 0 {
+			return f
+		}
+		sum += weight
+		if r < sum {
+			return f
+		}
+	}
+	// Shouldn't reach here
+	//just in case
+	return p.avail[0]
+}