The architecture of an event correlation service for adaptive middleware-based applications

Loosely coupled component communication driven by events is a key mechanism for building middleware-based applications that must achieve reliable qualities of service in an adaptive manner. In such a system, events that encapsulate state snapshots of a running system are generated by monitoring components. Hence, an event correlation service is necessary for correlating monitored events from multiple sources. The requirements for the event correlation raise two challenges: to seamlessly integrate event correlation services with other services and applications; and to provide reliable event management with minimal delay. This paper describes our experience in the design and implementation of an event correlation service. The design encompasses an event correlator and an event proxy that are integrated with an architecture for adaptive middleware components. The implementation utilizes the common-based event (CBE) specification and stateful Web service technologies to support the deployment of the event correlation service in a distributed architecture. We evaluate the performance of the overall solution in a test bed and present the results in terms of the trade-off between the flexibility and the performance overhead of the architecture.