Abstract

A system can be viewed from different perspectives, each focusing on a specific aspect such as availability, performance, security. Configurations reflect the manageable resources of the system, their attributes and organization which are necessary for the management of the system for each aspect. Thus, for management purposes a system is generally described through various partial configurations (also known as configuration fragments). To form a consistent system con-figuration, these independently developed configuration fragments need to be integrated together. The integration of configuration fragments is a challenging task. This is mainly due to over-lapping entities (different logical representations of the same system resource) in the configuration fragments and/or complex relationships among the entities of the different configuration fragments. At runtime the system may be reconfigured to meet certain/new requirements or in response to performance degradations. These changes may lead to inconsistency as some changes may violate the constraints between entities. Maintaining the consistency and adjusting the system configuration at runtime is another challenging task. In our research, we propose to handle these two important issues in an integrated manner. We define a model-based framework for configuration management. We use the Unified Modeling Language (UML) and its profiling mechanism for representing the configuration fragments. Using model weaving and model trans-formation techniques, we propose a solution for the integration of configuration fragments targeting specific system properties. To handle runtime changes, we propose a configuration validation and adjustment solution to check and preserve the consistency of the system configuration. We introduce a partial validation technique in which the runtime reconfigurations are checked against a reduced set of consistency rules instead of the complete set of rules and the reconfigurations are applied only if they are safe, i.e. they preserve the configuration consistency. For handling the changes that violate the consistency rules, we propose an adjustment technique to automatically resolve (if possible) the inconsistencies. This is achieved by propagating the changes in the configuration according to the system constraints following the possible impacts of the configuration entities on each other. Some heuristics are used to reduce the complementary changes and to limit the propagation. We evaluate the complexity of our adjustment technique and conduct experiments to evaluate its efficiency.
The Service Availability Forum middleware is used as an application domain in the examples throughout this thesis; however the proposed solutions are applicable in more general settings. We present proofs of concepts using different technologies. We use the Eclipse Modeling Framework (EMF) and Papyrus for implementing the UML profiles. The Atlas Model Weaver (AMW) and Atlas Transformation Language (ATL) are used to integrate the configuration fragments, and we also use the APIs of the Object Constraint Language (OCL) in the Eclipse environment and the Microsoft Z3 constraint solver to develop a prototype tool of our partial validation and adjustment agents.