In search of a detailed user tracking application

I am looking for a (preferably) open source application that meets a very specific set of requirements for user tracking. I need to be able to do the following:

1) track unique user sessions (easy)

2) track on screen clicks for prolonged periods of time (hours) and use the logs to recreate user behavior (automated preferred, but manual if no other options)

3) track multiple browsers and devices (although all will be browser-based)

4) minimal server overhead (most servers will have 4GB of memory)

5) runs on a Linux server

6) can track html5 and ajax generated from a java application

The kicker here is that the web app we're deve开发者_Go百科loping will run locally on small servers in thousands of distributed locations and can't rely on any connectivity to the Internet (just the location's own internal network). We also prefer open source because we are fairly budget constrained given that this would need to run on thousands of servers (not friendly to a commercial license).

I've searched stackoverflow and did a bit of other research, but I can't seem to find anything that fits that bill. Any advice would be GREATLY appreciated!