一种基于网格服务路线的异常处理方法

网格服务是提供一组定义明确接口并遵守一定规范的Web服务．网格服务异常(exception)是指在服务请求、响应和执行过程中可能发生的问题．网格服务异常处理与网格服务运行状态、上下文有关．网格服务异常处理的主要内容包括网格服务检查点(checkpoint)设置、服务运行跟踪、以及服务回卷(rollback)．传统处理方法是使用一个错误码：一个函数检测到错误，将错误码传送给调用者．这一处理过程可能要多级连续处理，直到该错误码被传送到响应该错误的处理函数．如果一个函数调用连接比较弱，将会造成整个处理过程失败．网格服务异常处理一方面应尽量减少传统处理单元内部错误代码繁殖的现象，另一方面要考虑服务异常向外部单元或网格服务传送的功能．这里，从网格系统结构出发，首先对网格服务异常处理进行讨论；然后提出了用于网格服务异常处理的A/B—Back算法；最后给出了基于Globus Toolkit 3．0的模拟实验结果分析．

An Exception Handling Method Based on Grid Service Routes

A grid service is a Web service that provides a set of well-defined interfaces and follows specific conventions. A grid service exception may occur in a process of behaviors related to requesting, responding, or running a grid service. Grid service exceptions deal with the run-time status and contextual information of grid services. A handler of exceptions mainly holds the configuration of a group of checkpoints, trace and rollback of services. The common approach to handling an exception is using a function to check out an error and sending the error code to the caller, which may need a multi-level and consecutive behaviors, till the error is sent to the function that responds it. If the linkage of these functions is weak, the whole process would fail. In a grid computing environment, an exception handler should not only reduce the internal propagation of error codes, but also make a transferable function to send the exception to an external unit or a grid service. In terms of the grid architecture, the exception handler of a grid service is discussed and then an A?B-Back algorithm is proposed, which is used to handle exceptions in a grid service. Finally, the test result based on the simulated experiment in Globus Toolkit 3.0 is given.