Web应用服务器的适应性失效检测

失效检测是分布式系统的基本可靠性保障技术,它对运行时系统的存活状态进行及时检测.作为网络分布计算环境中的主流中间件,Web应用服务器(Web application server,简称WAS)需要提供良好的检测机制,并且要能满足适应性的需求.适应性失效检测要求失效检测器能够根据应用需求和系统环境的变化而动态地改变检测的质量.首先给出了WAS的多层失效检测模型,然后基于失效检测器的服务质量规约,提出了适应性失效检测算法,并设计了一个WAS的适应性失效检测框架.它能够满足动态调整失效检测质量和灵活集成失效检测器的要求.该工作在OnceAS应用服务器中进行了实现,并给出了OnceAS平台上的实验及数据.

Adaptive Failure Detection in Web Application Server

Failure detection provides the ability of timely detecting the liveliness of runtime systems and is the basic reliability technology in distributed systems. Providing good failure detection is important to Web application server (WAS) that is the leading middleware in Web computing environment. Adaptive failure detection requires that failure detectors can dynamically adjust the detecting quality according to the requirements of applications and runtime environments. In this paper, the concepts and qualities of failure detectors are firstly discussed, and a multi-level model of failure detection in WAS is presented. Based on the QoS (quality of service) specification of failure detectors, an algorithm for adaptive failure detection is given, and an adaptive failure detection framework of WAS is designed, which can satisfy the requirements of dynamically adjusting qualities and flexible integration of failure detectors. The work has been implemented in OnceAS application server, and the experimental results are given in the end.