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Third USENIX Conference on Object-Oriented Technologies (COOTS), 1997

Interactive-Group Object-Replication Fault Tolerance for CORBA*

Brent E. Modzelewski
Electrical and Computer Engineering Dept.,
Worcester Polytechnic Institute

David Cyganski, Ph. D.
Electrical and Computer Engineering Dept.,
Worcester Polytechnic Institute

Marian V. Underwood
Lockheed Martin Corporation,
Government Electronic Systems


As more and more computers and workstations enter the workplace they are inevitably connected to a network. Networks provide the interconnection necessary for computers to share common data, peripherals and other system resources. Distributed computing allows network applications to access functions or processes on remote computers. Developing network applications specifically to interact and draw upon resources of multiple computers creates the groundwork for a distributed system or distributed computing environment (DCE).

An ideal distributed system is self monitoring and resilient to failures. In the event of a failure the system should dynamically reconfigure itself with automatic fail-over for applications that fall victim to the fault. Transparency of fault tolerant mechanisms is desirable, especially when introducing legacy applications into the distributed system. The reduction of application development efforts heavily relies on the availability of portable, non-invasive, fault tolerance providing extensions, which introduce mechanisms for uninterruptible service by insertion into existing distributed applications.

To test the potential for addressing some of these desired capabilities for a distributed system implemented within a CORBA distributed computing environment, the Interactive-Group Object-Replication (IGOR) system was developed. IGOR is a system of objects that provides fault tolerance through object replication by arranging replicas in fault tolerant groups which interact to provide access to redundant data and services. For purposes of portability, interoperability and to evaluate the CORBA environment, IGOR was designed with the constraint of lying entirely within the CORBA architecture and using IIOP as the communication protocol. This guarantees its portability over changes in platform and network technologies. The IGOR system is reconfigurable and its fault tolerance mechanisms are completely transparent to client applications.
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