Performance Monitoring in Digital Library Systems

Digital Libraries are systems for the management and transparent access of digital objects (text, sounds, images and videos) scattered throughout the Internet. In the recent years, the wide spread of those systems leads to an increased consideration of performance issues. What characterises digital library systems is their distribution to tens or hundreds of heterogeneous nodes and the fact that are integration of existing systems over the World Wide Web. These characteristics lead to significant performance variations and impose a new approach to performance monitoring. In this work, we designed and implemented a performance monitor for digital library systems. This monitor provides the necessary framework for performance studies and support of mechanisms for quality of service guarantees, dynamic adaptation of timeout and load balancing in digital library systems. As an example of its abilities, the monitor was used for a performance study of the NCSTRL-Dienst system, which led to the suggestion of various improvements in system's architecture. Finally, we designed a mechanism for dynamic adaptation of timeouts and tested some strategies for load balancing for the NCSTRL-Dienst system.