Eternal: fault tolerance and live upgrades for distributed object systems

The Eternal system supports distributed object applications that must operate continuously, without interruption of service, despite faults and despite upgrades to the hardware and the software. Based on the CORBA distributed object computing standard, the Eternal system replicates objects, invisibly and consistently, so that if one replica of an object fails, or is being upgraded, another replica is still available to provide continuous service. Through the use of interceptors, Eternal renders the object replication transparent to the application and also to the CORBA ORE. Consequently, Eternal is able to provide fault tolerance, and live hardware and software upgrades, for existing unmodified CORBA application programs, using unmodified commercial-off-the-shelf ORBs.