Reconfiguration in the Enterprise JavaBean Component Model

Reconfiguration is the process of applying planned changes to the communication, interconnection, componentization, or functionality of a deployed system. It is a powerful tool for achieving a variety of desirable properties of large-scale, distributed systems, including evolvability, adaptability, survivability, and continuous availability. Current approaches to reconfiguration are inadequate: some allow one to describe a system's range of configurations for a relatively broad class of system architectures, but do not provide a mechanism for actually carrying out a reconfiguration; others provide a mechanism for carrying out certain kinds of limited reconfigurations, but assume a specialized system architecture in order to do so. This paper describes our attempt at devising a reconfiguration mechanism for use with the popular and widely available Enterprise JavaBean (EJB) component container model. We describe extensions to the basic services provided by EJB to support the mechanism, a prototype implementation, and a case study of its application to a representative component-based distributed system.