Load Balancing in CORBA: A Survey Response to the Aggregated Computing RFI

CORBA is an industrial standard for distributed object-oriented applications covering aspects such as heterogeneity and interoperability of products of different vendors. However, the CORBA standard does not define any methods for load balancing and there is a considerable confusion of terms describing associated load balancing techniques. Starting from the general platformand language-independent CORBA object model, this paper presents a new hierarchical classification of possible load distribution methods for CORBA applications. The classification is a valuable starting point to identify the load balancing method that is appropriate for a given application. Furthermore, we show the relations to modern software design patterns and indicate the places in a CORBA application where load balancing components such as monitoring (obtaining load information), strategy (performing load distribution decisions), and control (executing the strategy decisions) may be integrated. Besides the discussion of the general object model as defined in the CORBA standard, we deal with concrete CORBAcompliant Object Request Brokers such as Orbix and VisiBroker. The presented techniques and examples are useful to systematically evaluate whether a given CORBA ORB can be used to implement a load balancing method as required by the application.