Message race detection for web services by an SMT-based analysis

The success of the cloud computing initiative is heavily dependent on realizing trustworthy Web Services. The trustworthiness of a Web Service is judged by four factors: security, privacy, reliability and business integrity. Web Services use message-passing for communication which opens the door for messages races. Messages race with each other when their order of arrival at a destination is not guaranteed and is affected non-deterministically by factors such as network latencies and scheduling variations. Message races are dangerous to Web Services because they can be unforeseen consequences of bugs, causing messages to arrive in an unexpected ordering. In this paper we present a novel approach for improving the reliability of Web Services by detecting message races using SMT-based analysis. We model a BPEL process as a Web Service Modeling Graph (WSMG). A WSMG model is then encoded into a set of SMT constraints. The satisfiability of these constraints means that message races will occur during the actual execution of the Web Service. Hence, we reduce the message race detection problem to constraint solving problem based on satisfiability modulo theories (SMT).