Apache Module mod_lbmethod_bybusyness

Description:	Pending Request Counting load balancer scheduler algorithm for mod_proxy_balancer
Status:	Extension
ModuleIdentifier:	lbmethod_bybusyness_module
SourceFile:	mod_lbmethod_bybusyness.c
Compatibility:	Split off from mod_proxy_balancer in 2.3

Summary

This module does not provide any configuration directives of its own. It requires the services of mod_proxy_balancer, and provides the bybusyness load balancing method.

Pending Request Counting Algorithm

Enabled via lbmethod=bybusyness, this scheduler keeps track of how many requests each worker is currently assigned at present. A new request is automatically assigned to the worker with the lowest number of active requests. This is useful in the case of workers that queue incoming requests independently of Apache, to ensure that queue length stays even and a request is always given to the worker most likely to service it the fastest and reduce latency.

In the case of multiple least-busy workers, the statistics (and weightings) used by the Request Counting method are used to break the tie. Over time, the distribution of work will come to resemble that characteristic of byrequests (as implemented by mod_lbmethod_byrequests).