Towards context-aware adaptive fault tolerance in SOA applications

Software components are expected to exhibit highly dependable characteristics in mission-critical applications, particularly in the areas of reliability and timeliness. Redundancy-based fault-tolerant strategies have long been used as a means to avoid a disruption in the service provided by the system in spite of the occurrence of failures in the underlying components. Adopting these fault-tolerance strategies in highly dynamic distributed computing systems, in which components often suffer from long response times or temporary unavailability, does not necessarily result in the anticipated improvement in dependability. In fact, as these dependability strategies are usually statically predefined and immutable, a change in the operational status (context) of any of the components involved may very well jeopardise the schemes' overall effectiveness. In this paper, a novel dependability strategy is introduced supporting advanced redundancy management, aiming to autonomously tune its internal configuration in view of changes in context. It is apparent from our preliminary experimentation that this strategy can effectively achieve an optimal trade-off between service reliability and performance-related factors such as timeliness and the degree of redundancy employed. A prototypical service-oriented implementation of the proposed adaptive fault tolerant strategy is presented thereafter, leveraging WS-* specifications to gather and disseminate contextual information.