Partial Scalability to Ensure Reliable Dynamic Reconfiguration

In order to be adapted to changes in user requirements and/or the environment, many software systems need to run continuously while they evolve. Most current approaches for such dynamic reconfiguration assume that the evolved system will behave as expected and thus will be reliable if the reconfiguration is consistent. This assumption may not correspond to reality because the delivered quality estimated previously could vary due to parameter changes at runtime. To ensure that the system acts correctly in the field after the reconfiguration, reliability of changes has to be checked at runtime. Existing approaches, however, are not applicable in highly available systems due to the possibility of imposing disruption to their running services. This paper aims to address this problem via improving the reliability of dynamic reconfiguration of component-based systems. To achieve this goal, our approach ensures reliability of changes before applying them in the running system. It leverages the benefits of explicit connectors to transparently deploy changes on idle resources and to temporarily run them along with the old system to evaluate if they meet the expected requirements. Whenever the reliability of changes is confirmed, they can be applied to the system.