Fixed scheduler handling backends update bug; removed redundant list …

…of backends

src/balance/weight.go

@@ -9,6 +9,7 @@ package balance
 import (
 	"errors"
 	"math/rand"
+	"sort"
 
 	"../core"
 )
@@ -20,16 +21,22 @@ type WeightBalancer struct{}
 
 /**
  * Elect backend based on weight strategy
- * TODO: Ensure backends are sorted in the same way (not it's not bacause of map in scheduler)
  */
 func (b *WeightBalancer) Elect(context core.Context, backends []*core.Backend) (*core.Backend, error) {
 
 	if len(backends) == 0 {
 		return nil, errors.New("Can't elect backend, Backends empty")
 	}
 
+	sorted := make([]*core.Backend, len(backends))
+	copy(sorted, backends)
+
+	sort.SliceStable(sorted, func(i, j int) bool {
+		return sorted[i].Target.String() < sorted[j].Target.String()
+	})
+
 	totalWeight := 0
-	for _, backend := range backends {
+	for _, backend := range sorted {
 		if backend.Weight <= 0 {
 			return nil, errors.New("Invalid backend weight 0")
 		}
@@ -39,7 +46,7 @@ func (b *WeightBalancer) Elect(context core.Context, backends []*core.Backend) (
 	r := rand.Intn(totalWeight)
 	pos := 0
 
-	for _, backend := range backends {
+	for _, backend := range sorted {
 		pos += backend.Weight
 		if r >= pos {
 			continue

src/server/scheduler/scheduler.go

@@ -70,9 +70,6 @@ type Scheduler struct {
 	/* Current cached backends map */
 	backends map[core.Target]*core.Backend
 
-	/* Current cached backends list (same as backends.list) but preserving order */
-	backendsList []*core.Backend
-
 	/* Stats */
 	StatsHandler *stats.Handler
 
@@ -225,24 +222,22 @@ func (this *Scheduler) HandleBackendLiveChange(target core.Target, live bool) {
 func (this *Scheduler) HandleBackendsUpdate(backends []core.Backend) {
 
 	updated := map[core.Target]*core.Backend{}
-	updatedList := make([]*core.Backend, len(backends))
 
-	for i, b := range backends {
+	for _, b := range backends {
 		oldB, ok := this.backends[b.Target]
 
 		if ok {
 			// if we have this backend, update it's discovery properties
 			updatedB := oldB.MergeFrom(b)
 			updated[oldB.Target] = updatedB
-			updatedList[i] = updatedB
-		} else {
-			updated[b.Target] = &b
-			updatedList[i] = &b
+			continue
 		}
+
+		b := b // b has to be local variable in order to make unique pointers
+		updated[b.Target] = &b
 	}
 
 	this.backends = updated
-	this.backendsList = updatedList
 }
 
 /**
@@ -252,7 +247,7 @@ func (this *Scheduler) HandleBackendElect(req ElectRequest) {
 
 	// Filter only live backends
 	var backends []*core.Backend
-	for _, b := range this.backendsList {
+	for _, b := range this.backends {
 
 		if !b.Stats.Live {
 			continue