Ben Laurie wrote:
Yes,like mod_backhand. mod_backhand is a load balancer that uses feedback from the server(s) it is load balancing. The types of performance metrics that can be APR'ized is quite large: memory usage, memory usage characteristics of specific applications, memory utilization of different aspects of different applications ('aspect' as in 'aspect oriented programs'), CPU usage for same, data arrival and departure rates, TCP layer performance (lost packet rate, thru-put, etc), application response time, relative capability of servers being load balanced (ie, CPU speed, bus speed, memory access speed, etc), blah blah... the list is virtually endless.Bill Stoddard wrote:
Rodent of Unusual Size wrote:
Rodent of Unusual Size wrote:
would anyone have any thoughts about the idea of adding an api to obtain the system load average? i ask because i need it for an httpd module i'm writing, and i've now got code for linux, freebsd, os x, sunos, and t64u..
no thoughts, uh.
load average is nice but it seems rather specialized and it doesn't really fit anywhere in apr[-util] that I see. load average is one performance metric; I can see where it might be useful to have a common interface for collecting all sorts of performance metrics. For example, if Apache is being used as a load balancer, you could collect performance state metrics from the servers being load balanced, feed that info back to the apache load balancer (on an HTTP response header field, via a special purpose HTTP POST request or out of band) and use it in your load balancing/routing algorithms.
Errr - mod_backhand?
My point: The range of performance metrics that may be of interest to, say, mod_backhand suggests it might be interesting to create a dedicated APR subproject for these types of APIs if we can forsee now that we will be adding more than just load average (count me as interested in such a project). I see goodness in adding a load average API to APR. However, aggressively going for a full suite of performance metric APIs would add bloat to APR, most of which would not be particularly useful to the majority of the APR user community.
Bill
