A Nested Invocation Suppression Mechanism for Cctive Replicated SOAP Systems

Abstract

The simple object access protocol (SOAP) is recognized as a more promising middleware for electronic commerce applications among other leading candidates such as CORBA. Many recent polls reveal however that security and reliability issues are major concerns that discourage people from engaging in electronic commerce transactions. We note that these issues are not adequately addressed in the current standard, i.e., SOAP 1.2. 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 issues 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 multithreading implementation. Existing solutions either solve RNI problem for single-threading cases or solve multithreading 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 so 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.