Research And Implementation Of DNS-Based Load Balancing Strategy Of Application Servers

Load balancing for application server cluster has become a hot spot research with Web-server clusters are adopted by more and more ISPs. Load balancing has different application forms for different requires or environments, and load balancing based on DNS are widely used in large websites because of its merits of simpleness and feasibility. But as its scheduling algorithm are commonly static methods, it has some problems in resource usage, reliability and expansibility, and service quality is affected by these demerits. So it become a researchable subject to improve load balancing algorithm and increase efficiency of application servers.Major works of this paper are:1. According to the demerits in DNS based load balancing, a DNS based dynamic linear load balancing strategy(DL) is proposed combined with node processing method of load balancing cluster and dynamic update of domain name system. This strategy focuses on load parameters such as CPU usage, memory usage, network I/O usages of application servers based on web service and computing them by a linear method and come out with a final load value. And load balancer selects a server with lowest load value to provide service.2. Simulated experiments are designed to verify advantage of DL strategy. Basic functions of DNS server are maintained and load information maintenance sub-module and scheduling sub-module are added in a simulated DNS program. Besides, a request strength adjustable client program is designed to simulate client requests. Round robin(RR) scheduling and DL scheduling are compared in average service time and experiment data show that time of DL is shorter than that of RR. Another part of experiment is to test performance of DL algorithm and find out which load parameter(es) is(are) most influential by adjust load weight factors.