Research And Implementation Of Fault Tolerant Web Services Composition Based On BPEL

With the development of Web Services technology, the Web Services are widelyused in many fields such as military, finance, and e-commerce, the key point to runthese systems successfully is the reliability of the web services. Different fromtraditional systems, Web Services are usually deployed in an uncertain networkenvironment, and because of the loosely coupled of Web Services, the reliability ofthem can not be guaranteed, therefore, how to improve the reliability of Web Servicesare attracting more and more attention.Fault tolerant technology is usually used to improve the reliability of software,there exists amounts of redundant Web Services on the Internet. Thus, it is a benefitmethod to improve the reliability of the composition of Web Services using faulttolerant technology. We first present the idea that providing fault tolerance only tothose key services in the system, and then propose two ranking algorithms based oncall relations and call frequency in services. WSRank1rank Web Services usingcriticality based on system operational profile; WSRank2not only uses the systemoperational profile, but also researches on reliability in every web service. Finally, onthe basis of analyzing the fault tolerant strategy of web services, this thesis proposesthe optimal fault tolerant strategy selection algorithm based on users’ conditions, andselects proper fault tolerance strategy for key services in the system. Based onstudying the reliability of the composition of Web Services, this thesis designs andachieves rules in the composition of Web Services using BPEL.Based on the ranking algorithms and the rules of BPEL fault tolerance, taking thebank system as an example, we design and implement the basic web services of it.Then, we choreograph the bank system using BPEL and test the reliability of thesystem after composition with SoapUI. The results show that the reliability of thesystem can not satisfy the user’s demands. Thus, we need to adopt fault tolerance toimprove the reliability of the whole system.First we obtain the system operationalprofile based on a large number of tests, and get the key service based on the rankingalgorithms. We provide fault tolerance according to users’ conditions and achievesystematic fault tolerance in the composition of web services. Finally, this thesis testson the fault tolerant systems, and analyzes the reliability results. Experimental resultshows that providing fault tolerance of key services can improve the reliability of thecomposition of services significantly, this plays a good role in balancing the reliabilityand costing.