一种异构Web服务器集群动态负载均衡算法

针对Web服务器集群系统中负载动态变化特性，提出了一种临界加速递减动态请求负载分配算法．通过负载权值的等效变换更准确地反映集群中单台服务器的当前负载状态；通过临界递减因子来有效抑制服务器可能出现的“拒绝访问”现象；通过随机概率分配方式替代固定转发分配方式，使访问负载的分布更均匀；通过实际测试获取算法中所需的计算参数，使配置操作更为简单．实验结果表明，该算法对较大负载的文件集的大密度访问情况效果明显。

A Dynamic Load-Balancing Algorithm for Heterogeneous Web Server Cluster

As increasing the embedded objects and the database searching tasks in Web Pages, there is larger difference among the loads of different server in a cluster system, which becomes more difficult for a heterogeneous Web server cluster to achieve high performance. In this paper, the authors present a dynamic load balancing algorithm MDC(Multiplicative Decrease in Critical area). For each of the servers in the cluster, the algorithm can more accurately evaluate the current load state by using the Equivalent Load Alternant and can more efficiently restrain the occurring of the reject service phenomenon by using a special MDC operator. Besides, the authors apply a method of random distributing base probability to assign each request to an appropriate server in terms of their weight. All the parameters that will be used in the algorithm can be acquired by simulated test. The authors also provide improved approximation results of above algorithm for the case where documents consist of relatively many embedded objects or database searches and lots of requests arrived the dispatcher synchronously.