tailieunhanh - Herald: Achieving a Global Event Notification Service

This paper presents the design philosophy and initial design decisions of Herald: a highly scalable global event notification system that is being designed and built at Microsoft Research. Herald is a distributed system designed to transparently scale in all respects, including numbers of subscribers and publishers, numbers of event subscription points, and event delivery rates. Event delivery can occur within a single machine, within a local network or Intranet, and throughout the Internet. Herald tries to take into account the lessons learned from the successes of both the Internet and the Web. Most notably, Herald is being designed, like the Internet, to operate correctly in the presence of numerous broken and disconnected components | Herald Achieving a Global Event Notification Service Luis Felipe Cabrera Michael B. Jones Marvin Theimer Microsoft Research Microsoft Corporation One Microsoft Way Redmond WA 98052 USA cabrera mbj theimer @ http mbj http theimer Abstract This paper presents the design philosophy and initial design decisions of Herald a highly scalable global event notification system that is being designed and built at Microsoft Research. Herald is a distributed system designed to transparently scale in all respects including numbers of subscribers and publishers numbers of event subscription points and event delivery rates. Event delivery can occur within a single machine within a local network or Intranet and throughout the Internet. Herald tries to take into account the lessons learned from the successes of both the Internet and the Web. Most notably Herald is being designed like the Internet to operate correctly in the presence of numerous broken and disconnected components. The Herald service will be constructed as a set of protocols governing a federation of machines within cooperating but mutually suspicious domains of trust. Like the Web Herald will try to avoid to the extent possible the maintenance of globally consistent state and will make failures part of the client-visible interface. 1. Introduction The function of event notification systems is to deliver information sent by event publishers to clients who have subscribed to that information. Event notification is a primary capability for building distributed applications. It underlies such now-popular applications as instant messenger systems friends on line stock price tracking and many others 7 3 13 16 10 15 . Until recently most event notification systems were intended to be used as part of specific applications or in localized settings such as a single machine a building or a campus. With the advent of generalized eCommerce frameworks interest has .