From 2511a1791d98b39ca017bec9cdc72e09cf0c067f Mon Sep 17 00:00:00 2001
From: Vladimir Mihailenco <vladimir.webdev@gmail.com>
Date: Tue, 7 Apr 2015 12:30:06 +0300
Subject: [PATCH] Use only master node address.

---
 cluster.go | 56 ++++++++++++++++++++++++------------------------------
 1 file changed, 25 insertions(+), 31 deletions(-)

diff --git a/cluster.go b/cluster.go
index 6fbc774..8790e12 100644
--- a/cluster.go
+++ b/cluster.go
@@ -26,11 +26,11 @@ type ClusterClient struct {
 	commandable
 
 	addrs   []string
-	slots   [][]string
+	slots   []string
 	slotsMx sync.RWMutex // protects slots & addrs cache
 
 	clients   map[string]*Client
-	clientsMx sync.RWMutex // protects clients
+	clientsMx sync.RWMutex
 
 	opt *ClusterOptions
 
@@ -106,12 +106,11 @@ func (c *ClusterClient) process(cmd Cmder) {
 	slot := hashSlot(cmd.clusterKey())
 
 	c.slotsMx.RLock()
-	defer c.slotsMx.RUnlock()
+	masterAddr := c.slots[slot]
+	c.slotsMx.RUnlock()
 
-	addrs := c.slots[slot]
-	if len(addrs) > 0 {
-		// First address is master.
-		client = c.getClient(addrs[0])
+	if masterAddr != "" {
+		client = c.getClient(masterAddr)
 	} else {
 		var err error
 		client, err = c.randomClient()
@@ -121,9 +120,6 @@ func (c *ClusterClient) process(cmd Cmder) {
 		}
 	}
 
-	// Index in the addrs slice pointing to the next replica.
-	replicaIndex := 1
-
 	for attempt := 0; attempt <= c.opt.getMaxRedirects(); attempt++ {
 		if ask {
 			pipe := client.Pipeline()
@@ -141,20 +137,11 @@ func (c *ClusterClient) process(cmd Cmder) {
 			return
 		}
 
-		// On network errors try another node.
+		// On network errors try random node.
 		if isNetworkError(err) {
-			if replicaIndex < len(addrs) {
-				// Try next available replica.
-				client = c.getClient(addrs[replicaIndex])
-				replicaIndex++
-				cmd.reset()
-				continue
-			} else {
-				// Otherwise try random node.
-				client, err = c.randomClient()
-				if err != nil {
-					return
-				}
+			client, err = c.randomClient()
+			if err != nil {
+				return
 			}
 			cmd.reset()
 			continue
@@ -197,16 +184,23 @@ func (c *ClusterClient) resetClients() (err error) {
 func (c *ClusterClient) setSlots(slots []ClusterSlotInfo) {
 	c.slotsMx.Lock()
 
-	c.slots = make([][]string, hashSlots)
-	for _, info := range slots {
-		for i := info.Start; i <= info.End; i++ {
-			c.slots[i] = info.Addrs
-		}
-		c.addrs = append(c.addrs, info.Addrs...)
-	}
-	c.addrs = removeDuplicates(c.addrs)
+	c.addrs = c.addrs[:0]
+	c.slots = make([]string, hashSlots)
 	c.resetClients()
 
+	seen := make(map[string]struct{})
+	for _, info := range slots {
+		masterAddr := info.Addrs[0]
+		for slot := info.Start; slot <= info.End; slot++ {
+			c.slots[slot] = masterAddr
+		}
+
+		if _, ok := seen[masterAddr]; !ok {
+			c.addrs = append(c.addrs, masterAddr)
+			seen[masterAddr] = struct{}{}
+		}
+	}
+
 	c.slotsMx.Unlock()
 }