From 58c9e16e62ab5486584d3d87b6f3b0686973809b Mon Sep 17 00:00:00 2001
From: Radu Ioan Fericean <radu@fericean.ro>
Date: Tue, 29 May 2012 23:15:09 +0300
Subject: [PATCH] using channel for balancer

---
 balancer/balancer.go | 42 +++++++++++++++++++++++++++---------------
 1 file changed, 27 insertions(+), 15 deletions(-)

diff --git a/balancer/balancer.go b/balancer/balancer.go
index 8f991f810..f11806dd1 100644
--- a/balancer/balancer.go
+++ b/balancer/balancer.go
@@ -27,7 +27,7 @@ import (
 type Balancer struct {
 	clientAddresses   []string // we need to hold these two slices because maps fo not keep order
 	clientConnections []*rpc.Client
-	balancerIndex     int
+	balancerChannel   chan *rpc.Client
 	mu                sync.RWMutex
 }
 
@@ -35,7 +35,18 @@ type Balancer struct {
 Constructor for RateList holding one slice for addreses and one slice for connections.
 */
 func NewBalancer() *Balancer {
-	r := &Balancer{balancerIndex: 0} // leaving both slices to nil
+	r := &Balancer{balancerChannel: make(chan *rpc.Client)} // leaving both slices to nil
+	go func() {
+		for {
+			if len(r.clientConnections) > 0 {
+				for _, c := range r.clientConnections {
+					r.balancerChannel <- c
+				}
+			} else {
+				r.balancerChannel <- nil
+			}
+		}
+	}()
 	return r
 }
 
@@ -43,6 +54,8 @@ func NewBalancer() *Balancer {
 Adds a client to the two  internal slices.
 */
 func (bl *Balancer) AddClient(address string, client *rpc.Client) {
+	bl.mu.Lock()
+	defer bl.mu.Unlock()
 	bl.clientAddresses = append(bl.clientAddresses, address)
 	bl.clientConnections = append(bl.clientConnections, client)
 	return
@@ -62,17 +75,19 @@ func (bl *Balancer) RemoveClient(address string) {
 	if index == -1 {
 		return
 	}
-	bl.mu.RLock()
-	defer bl.mu.RUnlock()
+	bl.mu.Lock()
+	defer bl.mu.Unlock()
 	bl.clientAddresses = append(bl.clientAddresses[:index], bl.clientAddresses[index+1:]...)
 	bl.clientConnections = append(bl.clientConnections[:index], bl.clientConnections[index+1:]...)
-	bl.balancerIndex = 0
+	<-bl.balancerChannel
 }
 
 /*
 Returns a client for the specifed address.
 */
 func (bl *Balancer) GetClient(address string) (*rpc.Client, bool) {
+	bl.mu.RLock()
+	defer bl.mu.RUnlock()
 	for i, v := range bl.clientAddresses {
 		if v == address {
 			return bl.clientConnections[i], true
@@ -85,20 +100,15 @@ func (bl *Balancer) GetClient(address string) (*rpc.Client, bool) {
 Returns the next available connection at each call looping at the end of connections.
 */
 func (bl *Balancer) Balance() (result *rpc.Client) {
-	bl.mu.Lock()
-	defer bl.mu.Unlock()
-	if bl.balancerIndex >= len(bl.clientAddresses) {
-		bl.balancerIndex = 0
-	}
-	if len(bl.clientAddresses) > 0 {
-		result = bl.clientConnections[bl.balancerIndex]
-		bl.balancerIndex++
-	}
+	bl.mu.RLock()
+	defer bl.mu.RUnlock()
 
-	return
+	return <-bl.balancerChannel
 }
 
 func (bl *Balancer) Shutdown() {
+	bl.mu.Lock()
+	defer bl.mu.Unlock()
 	var reply string
 	for i, client := range bl.clientConnections {
 		client.Call("Responder.Shutdown", "", &reply)
@@ -107,5 +117,7 @@ func (bl *Balancer) Shutdown() {
 }
 
 func (bl *Balancer) GetClientAddresses() []string {
+	bl.mu.RLock()
+	defer bl.mu.RUnlock()
 	return bl.clientAddresses
 }