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https://github.com/yaoweibin/nginx-sticky-module

clone from http://code.google.com/p/nginx-sticky-module/
https://github.com/yaoweibin/nginx-sticky-module

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clone from http://code.google.com/p/nginx-sticky-module/

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README 

        
Nginx Sticky Module 

--



Description:

	A nginx module to add a sticky cookie to be always forwarded the 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

	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] [hmac hmac_key=private_key] [no_fallback];

	  - 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: nothing. Let the browser handle this.



	  - 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.

	             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!

	             default: 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: 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.



Detail Mechanism

	see docs/sticky.{vsd,pdf}	



Contributing

	http://code.google.com/p/nginx-sticky-module/



TODO

	Stress

	Code review



Author

	Jerome Loyet 



Copyright & License

	This module is licenced under the BSD license.



	Copyright (C) 2010 Jerome Loyet (jerome at loyet dot net)



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

	modification, are permitted provided that the following conditions

	are met:



	1. Redistributions of source code must retain the above copyright

	notice, this list of conditions and the following disclaimer.



	2. Redistributions in binary form must reproduce the above copyright

	notice, this list of conditions and the following disclaimer in the

	documentation and/or other materials provided with the distribution.



	THIS SOFTWARE IS PROVIDED BY AUTHOR AND CONTRIBUTORS ``AS IS'' AND

	ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE

	IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE

	ARE DISCLAIMED.  IN NO EVENT SHALL AUTHOR OR CONTRIBUTORS BE LIABLE

	FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL

	DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS

	OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)

	HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT

	LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY

	OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF

	SUCH DAMAGE.