Message-oriented middleware with QoS awareness

Publish/subscribe messaging is a fundamental mechanism for interconnecting disparate services and systems in the service-oriented computing architecture. The quality of services (QoS) of the messaging substrate plays a critical role in the overall system performance as perceived by the end users. In this paper, we present the design and implementation of Harmony, an overlay-based messaging system that can manage the end-to-end QoS in wide-area publish/subscribe communications based on the application requirements. This is achieved through a holistic set of overlay route establishment and maintenance mechanisms, which actively exploit the diversity in the network paths and redirect the traffic over links with good quality, e.g., low latency and high availability. In order to cope with network dynamics and failures, Harmony continuously monitors the link quality and adapts the routes whenever their quality deteriorates below the application requirements. Harmony can operate on top of different data transport layers. When the transport layer has built-in message scheduling capability, Harmony takes advantage of it and utilizes a novel budget allocation scheme to control the scheduling behavior. We have fully implemented the Harmony messaging system, and our empirical experience has confirmed its effectiveness in providing end-to-end QoS in dynamic wide-area network environments.