How to implement new load balancing algorihtm in nginx? i found a new method from one paper to do a load balancing using content-based, and i want to try to realize this method in my own cluster in my laboratory..i spend 2 days google it

It depends how you detect which content is which, with Lua you can peek into requests at lower levels and then decide which upstream to use.

So you need to explain first what the test criteria is before we can think of a way to manage them.

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nginx for Windows http://nginx-win.ecsds.eu/

Actually i'm new in nginx, the truth is i still don't have a plan about this.. But i have one concept to cluster every request coming from client by requested header or page. Let's say i have cluster A and cluster B. If request contains only GET method or page that only showing result from querying database i will redirect the request to cluster A. Then if request contains POST method or page that contains some form to be filled, i will redirest the request to cluster B. In fact, i will use layer 7 to read this, or maybe there is another another way to read it.

Sorry for my bad english

You can use 'map' to set a variable based on several client browser values and use that variable to pass the request to whichever proxy or fcgi server.

Some reading stuff:
http://forum.nginx.org/read.php?2,194480,194990#msg-194990
http://www.cyberciti.biz/faq/nginx-redirect-backend-traffic-based-upon-client-ip-address/
http://www.kutukupret.com/2011/05/11/nginx-reverse-proxying-multiple-domains-using-map-module/

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nginx for Windows http://nginx-win.ecsds.eu/

Anyway thanks for the information about map, it's really nice thing.. But my problem isn't the way to pass the request to some server, i have to implement my own algorithm on nginx. It is have to be done with implementing my algorithm to know it's really work. The thing i hope i know is the way nginx load balance a cluster using chosen method (e.g. round robin, least conn)

Well without knowing what exactly you want to do we can't advice if, or how, it can be done :)

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nginx for Windows http://nginx-win.ecsds.eu/