环境：
| IP | 角色 | 软件 |
| 192.168.1.131 | proxy-server | nginx |
| 192.168.1.124:8080 | Tomcat1 | tomcat |
| 192.168.1.124:8081 | Tomcat2 | tomcat |
| 192.168.1.124:8082 | Tomcat3 | tomcat |
| 192.168.1.124:8083 | Tomcat4 | tomcat |
简单实现基于ip hash 实现会话保持
1 [root@gz01-nginx-proxy-master ~]# vim /usr/local/nginx/conf/nginx.conf
2 http {
3 include mime.types;
4 default_type application/octet-stream;
5 upstream tomcatlist {
6 ip_hash;
7 server 192.168.1.124:8080 weight=1;
8 server 192.168.1.124:8081 weight=2;
9 server 192.168.1.124:8082 weight=3;
10 server 192.168.1.124:8083 weight=4;
11 }
12 location / {
13
14 proxy_pass http://tomcatlist;
15
16 }
17 location ~* \.(jsp|do)$ {
18 proxy_pass http://tomcatlist;
19 proxy_set_header Host $host;
20 }
21 [root@gz01-nginx-proxy-master ~]# /usr/local/nginx/sbin/nginx -t
22 nginx: the configuration file /usr/local/nginx-1.8.1/conf/nginx.conf syntax is ok
23 nginx: configuration file /usr/local/nginx-1.8.1/conf/nginx.conf test is successful
24 [root@gz01-nginx-proxy-master ~]# /usr/local/nginx/sbin/nginx -s reload
站点建立测试页面
1 192.168.1.124:8080
2 <%@ page language="java" %>
3 <%@ page import="java.util.*" %>
4 <html>
5 <head>
6 <title>>Tomcat 192.168.1.124:8080 </title>
7 </head>
8 <body>
9
10 <h1><font color="blue">Tomcat 192.168.1.124:8080 </h1>
11 <table align="centre" border="1">
12 <tr>
13 <td>Session ID</td>
14 <% session.setAttribute("abc","abc"); %>
15 <td><%= session.getId() %></td>
16 </tr>
17 <tr>
18 <td>Created on</td>
19 <td><%= session.getCreationTime() %></td>
20 </tr>
21 </table>
22 </body>
23 </html>
24 192.168.1.124:8081
25 <%@ page language="java" %>
26 <%@ page import="java.util.*" %>
27 <html>
28 <head>
29 <title>>Tomcat 192.168.1.124:8081 </title>
30 </head>
31 <body>
32
33 <h1><font color="blue">Tomcat 192.168.1.124:8081 </h1>
34 <table align="centre" border="1">
35 <tr>
36 <td>Session ID</td>
37 <% session.setAttribute("abc","abc"); %>
38 <td><%= session.getId() %></td>
39 </tr>
40 <tr>
41 <td>Created on</td>
42 <td><%= session.getCreationTime() %></td>
43 </tr>
44 </table>
45 </body>
46 </html>
47 192.168.1.124:8082
48 <%@ page language="java" %>
49 <%@ page import="java.util.*" %>
50 <html>
51 <head>
52 <title>>Tomcat 192.168.1.124:8082 </title>
53 </head>
54 <body>
55
56 <h1><font color="blue">Tomcat 192.168.1.124:8082 </h1>
57 <table align="centre" border="1">
58 <tr>
59 <td>Session ID</td>
60 <% session.setAttribute("abc","abc"); %>
61 <td><%= session.getId() %></td>
62 </tr>
63 <tr>
64 <td>Created on</td>
65 <td><%= session.getCreationTime() %></td>
66 </tr>
67 </table>
68 </body>
69 </html>
70 192.168.1.124:8083
71 <%@ page language="java" %>
72 <%@ page import="java.util.*" %>
73 <html>
74 <head>
75 <title>>Tomcat 192.168.1.124:8083 </title>
76 </head>
77 <body>
78
79 <h1><font color="blue">Tomcat 192.168.1.124:8083 </h1>
80 <table align="centre" border="1">
81 <tr>
82 <td>Session ID</td>
83 <% session.setAttribute("abc","abc"); %>
84 <td><%= session.getId() %></td>
85 </tr>
86 <tr>
87 <td>Created on</td>
88 <td><%= session.getCreationTime() %></td>
89 </tr>
90 </table>
91 </body>
92 </html>
浏览器测试http://192.168.1.131
访问页面，一直匹配到192.168.1.124:8082的server 上，没有轮询；会话保持成功.
现在测试把192.168.124:8082关掉，在访问。
1 [root@gz01-tomcat-node01 ~]# /usr/local/tomcat/bbs.fox.com/bbs.tomcat stop
2 Using CATALINA_BASE: /usr/local/tomcat/bbs.fox.com
3 Using CATALINA_HOME: /usr/local/tomcat
4 Using CATALINA_TMPDIR: /usr/local/tomcat/bbs.fox.com/temp
5 Using JRE_HOME: /usr/local/jdk
6 Using CLASSPATH: /usr/local/tomcat/bin/bootstrap.jar:/usr/local/tomcat/bin/tomcat-juli.jar
虽然有负载均衡，会访问到下一台，但会话已经丢失；基于访问ip的hash策略，即当前用户的请求都集中定位到一台服务器中，这样单台服务器保存了用户的session登录信息，如果宕机，则等同于单点部署，会丢失，会话不复制。