The Design and Performance of a Scalable ORB Architecture for CORBA Asynchronous Messaging

Historically, method-oriented middleware, such as Sun RPC, DCE, Java RMI, COM, and CORBA, has provided synchronous method invocation (SMI) models to applications. Although SMI works well for conventional client/server applications, it is not well-suited for high-performance or real-time applications due to its lack of scalability. To address this problem, the OMG has recently standardized an asynchronous method invocation (AMI) model for CORBA. AMI provides CORBA with many of the capabilities associated traditionally with message-oriented middleware, without incurring the key drawbacks of message-oriented middleware. This paper provides two contributions to research on asynchronous invocation models for method-oriented middleware. First, we outline the key design challenges faced when developing the CORBA AMI model and describe how we resolved these challenges in TAO, which is our high-performance, real-time CORBA-compliant ORB. Second, we present the results of empirical benchmarks that demonstrate the performance benefits of AMI compared with alternative CORBA invocation models. In general, AMI based CORBA clients are more scalable than equivalent SMI based designs, with only a moderate increase in programming complexity.