支持服务优先级的多阶段服务模型研究*

多阶段服务模型是一种支持高并发、高吞吐的事件驱动服务应用架构，为使其更好地适应当前Internet上大部分应用提供区分等级服务的现状，提出了一种为该模型增加对带优先级请求支持的方法;定义了动态优先级，改进了随机早期检测算法以控制不同优先级事件的入队，并通过优先级动态提升防止低优先级事件被“饿死”。实验结果表明，改进后的模型在保持系统良好性能的基础上，满足了不同优先级请求的实时性和吞吐率需求。

Study on supporting priority-aware services in SEDA

SEDA is an event-driven server application architecture to support high concurrency and throughput. In order to adapt differentiated service provision which was the key to implement various levels of service in Internet applications currently, this paper proposed to incorporate the notion of priority in SEDA. Defined dynamic priority and improved RED algorithm to control events enqueue according to their priorities. Presented dynamic priority upgrading to keep events with lower priority from starvation. Experimental results show that the priority-aware SEDA can satisfy timeliness,throughput requirements of multi-level requests,and maintain the good performance of the system.