Providing QoS Customization in Distributed Object Systems

Distributed applications are increasingly using distributed object platforms such as CORBA, DCOM, and Java RMI to standardize object interactions. With this increased use comes the increased need for providing enhanced Quality of Service (QoS) attributes related to fault tolerance, security, and timeliness. This paper describes an approach to implementing such enhancements in a transparent, highly customizable, and portable manner. Specifically, the CQoS (Configurable QoS) architecture, which consists of application and distributed object platform-dependent interceptors and generic QoS components, is introduced. The generic QoS component are implemented using Cactus, a system for building highly configurable protocols and services in distributed systems. The CQoS architecture and the interfaces between the different components are described, together with implementations of QoS attributes using Cactus and interceptors on CORBA and Java RMI. Experimental results are given for a test application executing on a Linux cluster using Cactus/J, the Java implementation of Cactus. Compared with previous work, CQoS emphasizes portability across different distributed object platforms, while the use of Cactus allows custom combinations of fault-tolerance, security and timeliness attributes to be realized on a per-object basis in a straightforward way.