mod_athena 1.1.2

mod_athena is an Apache-based application load balancer for large systems.

This module is designed to allow httpd to act as a load balancer, either internally to apaches own mod_proxy (for reverse proxying), or externally to machines querying it.

Arbitrary statistics are sent to the engine via a simple GET plus query-string interface, from which it will then make decisions based on chosen algorithms.

If you are using commercial hardware or software to load balance protocols that can be handled by apaches mod_proxy, then you should be able to use this as a drop in replacement.

In the reverse http(s) proxy configuration, a request from a client is answered by apache. The request is handled by mod_proxy, which would then rewrite the url to substitute a mod_athena "AthFarm" for the target hostname.

httpd.conf: ProxyPass /reports/ http://farm_one/reports/

Then, mod_athena takes over the request. It will look up the farm, run the algorithm for that farm, and then substitute a real address for for the farm name. The result is handed back to mod_proxy to finish the request.

pseudo-code: http://farm_one/reports/ --> http://chosen_server/reports/

In the query configuration, a client (in this case probably another application) sends a GET request with a query string containing the desired farm(s) to httpd.

> fetch -q -o - http://my_athena/ath/balance/?farm_one chosen_server

The module engine will catch this request, run the appropriate algorithm(s), and return the appropriate result(s) as text content to the client. You can easily use mod_athena in both modes in the same instance of the engine.

mod_athena Apache module was written to solve the load balancing needs of our company, and is used in our production and quality assurance environments.