面向Web Service的动态负载均衡设计与实现

Web Services-Oriented Design and Implementation of Dynamic Load Balancing

负载均衡是分布式系统的资源管理模块,它的主要功能是合理和透明地在服务器之间分配系统负载,以达到系统的综合性能最优。基于中间件的负载均衡技术在整合异构系统、透明访问和扩展能力等方面具有优势。在中间模块上可以灵活实现多种负载均衡算法,来调整和满足不同应用的负载均衡需求,提高系统的扩展性、配置性、健壮性。本文参考分布式系统中的模型,构建了基于Web Service的负载均衡器,实现了动态负载均衡调度策略。为了准确地描述系统的负载,选择CPU利用率、内存利用率、系统响应时间、输入输出流量和进程数作为衡量系统负载的参量;为了避免因监测服务器而加大均衡器的压力,策略中将负载信息采集程序运行在机群内的各服务结点上,当相邻采集周期的负载差值超过标准值后调用均衡器上的Web服务,报告自身的负载状况,使均衡器根据负载信息进行同步操作,更换服务序列。最后通过仿真实验证明本策略在异构Web平台中具有可行性。

Load balancing is a resource managing block in a distributed system,whose main function is distributing system load logically and pellucidly between servers in order to achieve the optimization of the integrated performances.Load balancing technology can be integrated into middleware,which can be used in heterogeneous systems with access transparency and extensible capability.In the middle module we can achieve a variety of load balancing algorithms flexibly,in order to meet different load balancing demands of applications,and make the systems become more scalable,configurable,and robust.This paper designs a load balancer based on Web Services,and actualizes a dynamical load balancing scheduling policy according to the model of distributed systems.In order to describe system load more accurately,this paper chooses the CPU utilization,memory utilization,system response time,input and output streams and the process number as the parameters to measure the system load.In order to avoid increasing pressure on the balancer,this strategy will make the load information collection program run on the server nodes.When the value of the load difference from two interfacing acquisition cycles exceeds the standard,the collection program will call the Web Services on the balancer,reporting its own load status.And the balancer runs the synchronized operation according to the information collected from all the loads,and replaces the service sequence.Finally,the simulation experiment results shows that the dynamical load balancing scheduling policy performs well.