The Research And Design Of Load-Balancing Under CORBA Environment

Load balancing is an important part of CORBA Quality of Services (QoS), and it is also an indispensably technology when constructing a high-performance system. As the application environment of distributed systems are becoming complicated, and the customs are requiring for better performance of their service, researchers put forward a new technology, Content-based Load Balancing, to meet this point. For this technology has the ability to provide DOC (Distributed Object Computing) with more accurate and more adaptive load distribution ability considering more factors, it is gaining more and more attention in the field of Load Balancing (LB).This thesis focuses on systemically exploring and discussing how to design and implement a transparent and portable LB solution in CORBA environment. Although there is some LB technologies, such as Client-side Proxy, Object Group, Hub and Selector Module, have been applied to support LB, they all seem to bear some limitations on aspects of transparency and portability. OMG has defined an enhanced interceptor mechanism, Portable Interceptor (PI), based on the former request and message level interceptors. Since this version of PI earns the ability to redirect client requests and extract information from the intercepted messages, it provides an available pattern for us to implementing fine load balancing. Furthermore, PI was defined in the ORB level and an ORB independent standard, so this mechanism we can be used to get LB ability without modifying most part of the existing system and can be ported to other ORBs. After in-depth analysis of PI related CORBA mechanism and compare of current LB technologies used in,middleware, this thesis mainly expatiates a PI based CORBA LB design and also it gives some suggestions on the problems that may encounter in the further processes of implementation.