RTZen: Highly Predictable, Real-Time Java Middleware for Distributed and Embedded Systems

Distributed real-time and embedded (DRE) applications possess stringent quality of service (QoS) requirements, such as predictability, latency, and throughput constraints. Real-Time CORBA, an open middleware standard, allows DRE applications to allocate, schedule, and control resources to ensure predictable end-to-end QoS. The Real-Time Specification for Java (RTSJ) has been developed to provide extensions to Java so that it can be used for real-time systems, in order to bring Java's advantages, such as portability and ease of use, to real-time applications.In this paper, we describe RTZen, an implementation of a Real-Time CORBA Object Request Broker (ORB), designed to comply with the restrictions imposed by RTSJ. RTZen is designed to eliminate the unpredictability caused by garbage collection and improper support for thread scheduling through the use of appropriate data structures, threading models, and memory scopes. RTZen's architecture is also designed to hide the complexities of RTSJ related to distributed programming from the application developer. Empirical results show that RTZen is highly predictable and has acceptable performance. RTZen therefore demonstrates that Real-Time CORBA middleware implemented in real-time Java can meet stringent QoS requirements of DRE applications, while supporting safer, easier, cheaper, and faster development in real-time Java

Design and Performance of a Modular Portable Object Adapter for Distributed, Real-Time, and Embedded CORBA Applications

ZEN is a CORBA ORB designed to support distributed, realtime, and embedded (DRE) applications that have stringent memory constraints. This paper discusses the design and performance of ZENs portable object adapter (POA) which is an important component in a CORBA object request broker (ORB). This paper makes the following three contributions to the study of middleware for memory-constrained DRE applications. First, it presents three alternative designs of the CORBA POA. Second, it explains how design patterns can be applied to improve the quality and performance of POA implementations. Finally, it presents empirical measurements based on the ZEN ORB showing how memory footprint can be reduced significantly while throughput is comparable to a conventional ORB implementation