Intelligent, Dynamic Load Balancing Mechanism for Apache HTTP Server

Abstract

Apache is a platform independent HTTP server which runs on modern operating systems including UNIX, FreeBSD, Linux, Solaris, Novell NetWare, Mac OS X, Microsoft Windows, OS/2, TPF, and eComStation. Enterprise web applications are expected to be scalable, fast and reliable and able to handle fail-over behavior. Thus the web server must supports for the above features to give reliable, exible, and e ective services to the internet users. Apache HTTP server is popular because it supports above features for enterprise web applications. It can be con gured to share the load among a set of workers which are responsible for work under a particular web server or a Balancer. A worker is another Apache server or an- other web container or application server that is compliant with Apache HTTPD. Inside the Apache, each module is responsible for handle a particular task. Module mod proxy balancer is responsible for the load balancing of Apache HTTPD 2.2 for clustering environment. It provides load balancing support for HTTP, FTP and AJP13 protocols. The mod Proxy Balancer is policy based load balancer. Thus we have to select load bal- ancing algorithm and set the requests distribution ratio among the cluster workers, before the server startup. It does not really communicate with the backend server when get de- cision about nding optimal worker but its responsible for the management of several real workers. The load balancer enables requests to be shared among workers via three methods: request counting, weighted tra c counting, and pending request counting algorithms. But these algorithms are not su ciently enough for intelligent load balancing mechanism. These algorithms do not measure about the workers feasibility or ability of processing next request before forwarding the request to the workers. We have developed a new module mod dynamic balancer for Apache HTTP 2.2 server. Load balancing mechanism can be enhanced by introducing dynamic load balancing mechanism for the Apache. This enables balance the load among the workers intelligently. We have developed this module for Apache-Tomcat integrations on UNIX environment.