Web对象访问特征模拟器的设计与实现

Web缓存是一个提高Web性能非常有效的方法，它可以位于网络的不同位置：客户端，代理服务器端，服务器端。研究表明Web缓存命中率可以达到30％-50％。Web缓存在应用中最大的问题就是Web缓存管理，研究Web访问特征是有效进行Web缓存管理的基础。Web日志生成模拟器对于研究Web缓存系统有很大地帮助，目前有两种方法模拟生成Web访问日志：日志驱动方法，数学模拟方法。日志驱动方法利用对历史日志进行变换来模拟生成新的日志，数学模拟方法在充分研究Ⅵ协对象访问特征的基础上，通过建立数学模型来模拟生成Web日志。该文通过分析Web对象访问特征，采用数学模拟方法分别模拟了Web对象高频区及低频区流行度特征，Web对象大小重尾分布特征，Web访问的时间局部性特征；设计并实现了一个Web日志模拟生成器WEBSIM。该模拟器不仅可以模拟生成Web对象访问日志，而且具有较大的灵活性，为进一步研究Web缓存技术和预取技术提供依据。

Design and Implementation of Simulator of Web Object Access Characteristics

Web object caching is one of the most prevalent approaches for improving Web performance. Caching can be applied at several locations: at the client, at the proxy server, at the server. Research shows that the hit ratio of web caching can reach 30% - 50%. The most important problem in the application of web caching is how to manage web cache efficiently. Studying the web access characteristics is the foundation for managing web cache efficiently. Web LOG generation simulator plays an important role in studying web caching system. So far there are two approaches for synthesizing web access workloads: the trace- based approach and the mathematical analytical approach. The trace- based approach uses a history trace to generate a new workload. The mathematical analytical approach creates mathematical models to generate workloads. After analysing the web object access characteristics, this paper uses mathematical analytical approach to design and implement a web LOG simulator: WEBSIM, in which the web object popularity distribution, web object size distribution and web temporal locality are simulated. WEBSIM not only can synthesize web object access workload, but also has higher flexibility, and provides base for further web caching and prefetching study.