0 工作原理
Session Sticky 模块在upstream 返回响应后，向客户的浏览器写入 Cookie ，默认名为route ，保存的内容是一个 md5 码。
之后，模块接收到客户浏览器的请求时，就根据 route 来决定将请求转发到 upstream中哪台服务器上。
这是源码包中附带的流程图，将模块的处理流程描述的非常清晰：
1 下载 Session Sticky
wget https://nginx-sticky-module.googlecode.com/files/nginx-sticky-module-1.1.tar.gz
2 安装模块
如果 Nginx 之前已经安装了，可以通过 nginx -V 命令查看当时编译的参数。在参数后面追加安装 Session Sticky 模块的参数，
避免影响之前 Nginx 已有模块。
进入 nginx 源码目录，执行命令：
./configure … --add-module=/usr/local/src/nginx-sticky-module-1.1
make
make install
3 激活模块
在 upstream块中添加 sticky; 即可激活Session Sticky模块。
upstream {
sticky;
server 127.0.0.1:9000;
server 127.0.0.1:9001;
server 127.0.0.1:9002;
}
4 可用选项
The "sticky" command can take several arguments to control its behaviour:
sticky [name=route] [domain=.foo.bar] [path=/] [expires=1h] [hash=index|md5|sha1] [no_fallback];
| Configuration |
Description |
Parameters |
Default Value |
| name |
the name of the cookie used to track the persistant upstream srv |
can be any string |
"route" |
| domain |
the domain in which the cookie will be valid |
can be any string |
nothing. Let the browser handle this. |
| path |
the path in which the cookie will be valid |
can be any path |
nothing. Let the browser handle this. |
| expires |
the validity duration of the cookie |
must be a duration greater than one second |
nothing. It's a session cookie |
| hash |
the hash mechanism to encode upstream server. It cant' be used with hmac |
md5|sha1 |
md5 |
| hmac |
The HMAC hash mechanism to encode upstream server. It's like the hash mechanism but it uses hmac_key to secure the hashing. It can't be used with hash. |
md5|sha1 |
none |
| hmac_key |
The key to use with hmac. It's mandatory when hmac is set. |
can be any string |
none |
| no_fallback |
When this flag is set, nginx will return a 502 (Bad Gateway orProxy Error) if a request comes with a cookie and the corresponding backend is unavailable. |
no arguments |
none |