Sticky是nginx的一个模块，它是基于cookie的一种nginx的负载均衡解决方案，通过分发和识别cookie，来使同一个客户端的请求落在同一台服务器上，默认标识名为route
1.客户端首次发起访问请求，nginx接收后，发现请求头没有cookie，则以轮询方式将请求分发给后端服务器。
2.后端服务器处理完请求，将响应数据返回给nginx。
3.此时nginx生成带route的cookie，返回给客户端。route的值与后端服务器对应，可能是明文，也可能是md5、sha1等Hash值
4.客户端接收请求，并保存带route的cookie。
5.当客户端下一次发送请求时，会带上route，nginx根据接收到的cookie中的route值，转发给对应的后端服务器。

Nginx Sticky Module

modified and extended version; see Changelog.txt

Description

A nginx module to add a sticky cookie to be always forwarded to the same upstream server.

When dealing with several backend servers, it's sometimes useful that one client (browser) is always served by the same backend server (for session persistance for example).

Using a persistance by IP (with the ip_hash upstream module) is maybe not a good idea because there could be situations where a lot of different browsers are coming with the same IP address (behind proxies)and the load balancing system won't be fair.

Using a cookie to track the upstream server makes each browser unique.

When the sticky module can't apply, it switchs back to the classic Round Robin Upstream or returns a "Bad Gateway" (depending on the no_fallback flag).

Sticky module can't apply when cookies are not supported by the browser

Sticky module is based on a "best effort" algorithm. Its aim is not to handle security somehow. It's been made to ensure that normal users are always redirected to the same backend server: that's all!

Installation

You'll need to re-compile Nginx from source to include this module. Modify your compile of Nginx by adding the following directive (modified to suit your path of course):

./configure ... --add-module=/absolute/path/to/nginx-sticky-module-ng
make
make install

Usage

upstream {
  sticky;
  server 127.0.0.1:9000;
  server 127.0.0.1:9001;
  server 127.0.0.1:9002;
}

  sticky [name=route] [domain=.foo.bar] [path=/] [expires=1h] 
       [hash=index|md5|sha1] [no_fallback] [secure] [httponly];

• name: the name of the cookies used to track the persistant upstream srv; default: route

• domain: the domain in which the cookie will be valid default: nothing. Let the browser handle this.

• path: the path in which the cookie will be valid default: /

• expires: the validity duration of the cookie default: nothing. It's a session cookie. restriction: must be a duration greater than one second

• hash: the hash mechanism to encode upstream server. It cant' be used with hmac. default: md5

  • md5|sha1: well known hash
  • index: it's not hashed, an in-memory index is used instead, it's quicker and the overhead is shorter Warning: the matching against upstream servers list is inconsistent. So, at reload, if upstreams servers has changed, index values are not guaranted to correspond to the same server as before! USE IT WITH CAUTION and only if you need to!

• 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: well known hash default: none. see hash.

• hmac_key: the key to use with hmac. It's mandatory when hmac is set default: nothing.

• no_fallback: when this flag is set, nginx will return a 502 (Bad Gateway or Proxy Error) if a request comes with a cookie and the corresponding backend is unavailable.

• secure enable secure cookies; transferred only via https

• httponly enable cookies not to be leaked via js

Detail Mechanism

• see docs/sticky.{vsd,pdf}

Issues and Warnings:

• when using different upstream-configs with stickyness that use the same domain but refer to different location - configs it might be wise to set a different path / route -
  option on each of this upstream-configs like described here: https://bitbucket.org/nginx-goodies/nginx-sticky-module-ng/issue/7/leaving-cookie-path-empty-in-module

• sticky module does not work with the "backup" option of the "server" configuration item.

• sticky module might work with the nginx_http_upstream_check_module (up from version 1.2.3)
• sticky module may require to configure nginx with SSL support (when using "secure" option)

Contributing

• please send/suggest patches as diffs
• tickets and issues here: https://bitbucket.org/nginx-goodies/nginx-sticky-session-ng

Downloads

• tarballs are available via tags from the rep https://bitbucket.org/nginx-goodies/nginx-sticky-module-ng/downloads

TODO

see Todo.md

Authors & Credits

• Jerome Loyet, initial module
• Markus Linnala, httponly/secure-cookies-patch
• Peter Bowey, Nginx 1.5.8 API-Change
• Michael Chernyak for Max-Age-Patch
• anybody who suggested a patch, created an issue on bitbucket or helped improving this module

Copyright & License

This module is licenced under the BSD license.

Copyright (C) 2010 Jerome Loyet (jerome at loyet dot net)
Copyright (C) 2014 Markus Manzke (goodman at nginx-goodies dot com)


Redistribution and use in source and binary forms, with or without
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