Dynamic Reconfiguration and Load Distribution in Component Middleware
Maarten Wegdam · University of Twente Research Information · 2003
Large-scale distributed systems, such as telematics systems, are often built using component-middleware technologies (e.g., CORBA). Middleware offers distribution transparencies. This means that complexities related to the distribution are hidden from the application developers by embedding the distribution aspects in the middleware. Component middleware is middleware that uses component concepts such as encapsulation and well-defined interfaces. This thesis proposes a new approach for the design of Quality of Service (QoS) mechanisms in component middleware. The specific QoS mechanisms that we propose in this thesis are (i) a new dynamic reconfiguration mechanism, which improves the availability by allowing online replacements and migrations of application components, and (ii) a new load distribution mechanism, which improves the performance of application components. Important characteristics of these QoS mechanisms are: (i) they are dynamic, (ii) they do not rely on specific network or operating system QoS functionality, and (iii) they are transparent for the developer of application components. We achieve transparency by using message reflection techniques in the middleware layer. A CORBA-based prototype serves as a proof of concept for our approach and our QoS mechanisms. M