Extracting dynamic dependencies between web services using vector clocks

Service Oriented Architecture (SOA) enables organizations to react to requirement changes in an agile manner and to foster the reuse of existing services. However, the dynamic nature of service oriented systems and their agility bear the challenge of properly understanding such systems. In particular, understanding the dependencies among services is a non trivial task, especially if service oriented systems are distributed over several hosts belonging to different departments of an organization. In this paper, we propose an approach to extract dynamic dependencies among web services. The approach is based on the vector clocks, originally conceived and used to order events in a distributed environment. We use the vector clocks to order service executions and to infer causal dependencies among services. We show the feasibility of the approach by implementing it into the Apache CXF framework and instrumenting the SOAP messages. We designed and executed two experiments to investigate the impact of the approach on the response time. The results show a slight increase that is deemed to be low in typical industrial service oriented systems.