| Summary: | 博士 === 國立臺灣科技大學 === 電子工程系 === 92 === Zwass suggested that electronic commerce activities are built on five fundamental infrastructure technologies, including messaging and information distribution infrastructure. This infrastructure is usually implemented with distributed middleware, such as OMG’s CORBA, Microsoft’s DCOM and W3C’s SOAP. Many recent polls revealed, however, that security and reliability issues are major concerns that discourage people from engaging in EC transactions. We noticed that the fault-tolerance issue is somewhat neglected in the current SOAP standard. We adopted the interfaces of fault tolerant CORBA and the developing experience on fault tolerant object service on CORBA to propose a fault tolerant web service called fault tolerant SOAP or FT-SOAP through which web services can be built with higher resilience to failure. There are many architectural differences between SOAP and CORBA. We have discussed the differences of design and implementations for fault tolerance service on both SOAP and CORBA. One of the major contributions of this work is to discuss the impact on FT-SOAP design due to these architectural differences. Our experience shows that web services built on a SOAP framework enjoy higher flexibility as opposed to those built on CORBA. We also point out the limitations of the current feature sets of SOAP 1.1. We believe our experience is valuable not only to the fault-tolerance community, but also to other communities as well, in particular, to those who are familiar with the CORBA platform. We notice that active replication is a common approach to building readily available and highly reliable distributed software applications. The redundant nested invocation (RNI) problem arises when servers in a replicated group issue nested invocations to other server groups in response to a client invocation. Automatic suppression of RNI from active group is always a desirable function, yet this function usually requires careful if not complex design. The design complexity increases if the system involves multi-threading implementation. Existing solutions either solve the RNI problem for single-threading cases or solve multi-threading cases at the expense of portability. In this work, we propose a mechanism to perform auto-suppression of redundant nested invocation on an active replication fault tolerant web service. Our approach is portable such that the web service running on our platform is able to interact with any other SOAP applications. Our preliminary experiments show that the proposed auto-suppression mechanism is efficient in most cases.
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