Apache Dynamic Update for Feedback Control of Computing Resources

This paper shows an environment for performing data collection in the computational system that provides the response service to “HTTP” requests and makes interventions in the values of the available parameters in order to control the system automatically in the closed loop. The parameters to be obtained as endogenous variables of the computational system are MaxRequestWorks and KeppAliveTimeOut, and the exogenous ones will be the amount of memory consumed and the percentage of processor occupation time. The tool developed modifies neither the source code of the response software to the clients' “HTTP” requests nor the operating system code of the host computer, being non-intrusive regarding original system configuration. A proportional-integral (PI) controller was designed in order to keep the average perceived time response of “HTTP” messages regulated. The experimental tests carried out on an Apache Web server show the improvement obtained on the system's time response.