A Preliminary Study of Suppressing Redundant Nested Invocations from a Web Service with Active Replication

Zwass (1996) suggested that middleware and message service is one of the five fundamental technologies used to realize electronic commerce (EC). The Simple Object Access Protocol (SOAP) is recognized as a more promising middleware for EC applications among other leading candidates such as CORBA. We notice that the fault-tolerance issue is somewhat neglected in the current standard, that is, SOAP 1.1. We therefore proposed a fault tolerant Web service called fault-tolerant SOAP or FT-SOAP through which Web services can be built with higher resilience to failure. Active replication is a common approach to building highly available and 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. In this work, we propose a mechanism to perform auto-suppression of redundant nested invocation in an active replication FT-SOAP system. Our approach ensures the portability requirement of a middleware, especially for FT-SOAP. The current design of the suppression mechanism itself does not consider the fault-tolerance issue. In other words, it suffers from the single-point of failure. Furthermore, the preliminary performance results indicates significant performance penalty due to inefficient SOAP invocations. More comprehensive experiments are needed to further investigate the feasibility of the current approach in the context of system performance.