Research On Dynamic Reconfiguration Technology In Component-Oriented Complex Software System

With the increasing tendency of applying distributed technology in wide range of critical domains, more and more distributed systems must provide uninterrupted services, such as aerial navigation system, satellite positioning system, financial system and national communicating facilities etc. With the effective support from the technology of dynamic reconfiguration, these systems can evolve online, so that they can follow the development of technology, implement QOS control, meet various requirements of customers and adapt to complicated and changeable environment. As the scale of distributed systems keeps expanding, the systems are more and more complex and harder to be managed and maintained. To solve these problems and to improve the adaptability, the system must be autonomic to manage itself and react to each unexpected incident through dynamic reconfiguration. Today lots of research on dynamic reconfiguration has been carried out. Aiming at some problems of current research on correctness, functionality and performance, this thesis makes the following contributions:1. The reflecting mechanism and the reflecting system are the foundations of evolvement online. So firstly the thesis puts forward the reflecting dynamic reconfiguration model named RDRM which comprises the reflecting mechanism and the reflecting system. For the dynamic reconfiguration system, RDRM depicts its reflecting nature, describes its working process, and points out its composing elements, thus provides a unified framework to analyze and evaluate different dynamic reconfiguration systems. Based on RDRM model, the thesis analyzes the association among all the composing elements of the dynamic reconfiguration system, and find out the strong active elements, including the intercessory protocol which exhibits the dynamic reconfiguration ability and the base platform which decides the efficiency of dynamic reconfiguration system. This important theoretic conclusion provides the guidance for the further research on dynamic reconfiguration.2. The system consistency is the correctness constraint of the intercessory protocol. And how to preserve the system consistency is the key technology of the intercessory protocol. Therefore the thesis focuses on the consistency system. Firstly the concept of behavioral consistency is defined which unifies mutual consistency and local consistency so that the integrity of the interactive and local behaviors would be preserved more strictly and the corresponding process complexity would be reduced effectively. Then in order to carry out dynamic reconfiguration correctly, flexibly and efficiently in different scenario, a complete set of approaches, including strong andweak behavioral consistency preserving approaches, are proposed to preserve the behavioral consistency, component state consistency, application state consistency and reference consistency.3. The thesis designs flexible and efficient intercessory protocol. Eight reconfiguration algorithms are presented separately to implement eight basic reconfiguration intentions, including component creation, component removal, component replacement, component migration, connection creation, connection removal, connection redirection and component attribute configuration. Moreover, all the algorithms are proved to preserve four kinds of consistency mentioned above. This part of work not only forms the basis to realize compound reconfiguration intentions with complex configuration and powerful functions, but also enables the stateful component to evolve online.4. Based on StarCCM which conforms to CORBA Component Model specification and has powerful reflecting ability, the thesis maps the RDRM model to the concrete software entities on StarCCM, and hence builds a dynamic reconfiguration platform named StarDRP. Both the theoretic analysis from the above and the experiment on the function and performance demonstrate that StarDRP can meet the requirement of the applications with its powerful dynamic reconfiguration ability, high accuracy and high performance.