From a89f64abf999b0cc7b255ae3b77312ba982edc37 Mon Sep 17 00:00:00 2001
From: Xargin <cao1988228@163.com>
Date: Fri, 1 Jun 2018 14:55:50 +0800
Subject: [PATCH] lb done

---
 SUMMARY.md                     |  1 +
 ch6-web/ch6-12-load-balance.md | 62 ++++++++++++++++++++++++++++++++--
 2 files changed, 61 insertions(+), 2 deletions(-)

diff --git a/SUMMARY.md b/SUMMARY.md
index 291b3a0..3e418cd 100644
--- a/SUMMARY.md
+++ b/SUMMARY.md
@@ -45,6 +45,7 @@
    * [6.4. Validator请求校验](ch6-web/ch6-04-validator.md)
    * [6.5. Database和数据库打交道](ch6-web/ch6-05-database.md)
    * [6.8. Layout大型web项目分层](ch6-web/ch6-08-layout-of-web-project.md)
+   * [6.12. Load-balance负载均衡](ch6-web/ch6-12-load-balance.md)
 * [附录](appendix/readme.md)
    * [附录A: Go语言常见坑](appendix/appendix-a-trap.md)
    * [附录B: 参考资料](appendix/appendix-b-ref.md)
diff --git a/ch6-web/ch6-12-load-balance.md b/ch6-web/ch6-12-load-balance.md
index a178518..d264a05 100644
--- a/ch6-web/ch6-12-load-balance.md
+++ b/ch6-web/ch6-12-load-balance.md
@@ -86,8 +86,8 @@ func request(params map[string]interface{}) error {
 
 ```go
 func shuffle(indexes []int) {
-    lastIdx := len(indexes) - 1
     for i:=len(indexes); i>0; i-- {
+        lastIdx := i - 1
         idx := rand.Int(i)
         indexes[lastIdx], indexes[idx] = indexes[idx], indexes[lastIdx]
     }
@@ -119,4 +119,62 @@ rand.Seed(time.Now().UnixNano())
 
 ## 负载均衡算法效果验证
 
-我们这里不考虑加权负载均衡的情况，既然名字是负载“均衡”。那么最重要的就是均衡。
+我们这里不考虑加权负载均衡的情况，既然名字是负载“均衡”。那么最重要的就是均衡。我们把开篇中的 shuffle 算法，和之后的 fisher yates 算法的结果进行简单地对比：
+
+```go
+package main
+
+import (
+    "fmt"
+    "math/rand"
+    "time"
+)
+
+func init() {
+    rand.Seed(time.Now().UnixNano())
+}
+
+func shuffle1(slice []int) {
+    for i := 0; i < len(slice); i++ {
+        a := rand.Intn(len(slice))
+        b := rand.Intn(len(slice))
+        slice[a], slice[b] = slice[b], slice[a]
+    }
+}
+
+func shuffle2(indexes []int) {
+    for i := len(indexes); i > 0; i-- {
+        lastIdx := i - 1
+        idx := rand.Intn(i)
+        indexes[lastIdx], indexes[idx] = indexes[idx], indexes[lastIdx]
+    }
+}
+
+func main() {
+    var cnt1 = map[int]int{}
+    for i := 0; i < 1000000; i++ {
+        var sl = []int{0, 1, 2, 3, 4, 5, 6}
+        shuffle1(sl)
+        cnt1[sl[0]]++
+    }
+
+    var cnt2 = map[int]int{}
+    for i := 0; i < 1000000; i++ {
+        var sl = []int{0, 1, 2, 3, 4, 5, 6}
+        shuffle2(sl)
+        cnt2[sl[0]]++
+    }
+
+    fmt.Println(cnt1, "\n", cnt2)
+}
+
+```
+
+输出：
+
+```shell
+map[0:224436 1:128780 5:129310 6:129194 2:129643 3:129384 4:129253]
+map[6:143275 5:143054 3:143584 2:143031 1:141898 0:142631 4:142527]
+```
+
+分布结果和我们推导出的理论是一致的。