tailieunhanh - SEDA: An Architecture for WellConditioned, Scalable Internet Services

We propose a new design for highly concurrent Internet services, which we call the staged event-driven architecture (SEDA). SEDA is intended to support massive concurrency demands and simplify the construction of well-conditioned services. In SEDA, applications consist of a network of event-driven stages connected by explicit queues. This architecture allows services to be well-conditioned to load, preventing resources from being overcommitted when demand exceeds service capacity. SEDA makes use of a set of dynamic resource controllers to keep stages within their operating regime despite large fluctuations in load. We describe several control mechanisms for automatic tuning and load conditioning, including thread pool sizing, event batching, and adaptive load shedding. We present. | SEDA An Architecture for Well-Conditioned Scalable Internet Services Matt Welsh David Culler and Eric Brewer Computer Science Division University of California Berkeley mdw culler brewer @ Abstract We propose a new design for highly concurrent Internet services which we call the staged event-driven architecture SEDA . SEDA is intended to support massive concurrency demands and simplify the construction of well-conditioned services. In SEDA applications consist of a network of event-driven stages connected by explicit queues. This architecture allows services to be well-conditioned to load preventing resources from being overcommitted when demand exceeds service capacity. SEDA makes use of a set of dynamic resource controllers to keep stages within their operating regime despite large fluctuations in load. We describe several control mechanisms for automatic tuning and load conditioning including thread pool sizing event batching and adaptive load shedding. We present the SEDA design and an implementation of an Internet services platform based on this architecture. We evaluate the use of SEDA through two applications a high-performance HTTP server and a packet router for the Gnutella peer-to-peer file sharing network. These results show that SEDA applications exhibit higher performance than traditional service designs and are robust to huge variations in load. 1 Introduction The Internet presents a computer systems problem of unprecedented scale that of supporting millions of users demanding access to services that must be responsive robust and always available. The number of concurrent sessions and hits per day to Internet sites translates into an even higher number of I O and network requests placing enormous demands on underlying resources. Yahoo receives over billion page views daily 62 and AOL s Web caches service over 10 billion hits a day 2 . Moreover Internet services experience huge variations in service load with bursts coinciding with .

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