An adaptive quality of service aware middleware for replicated services

TitleAn adaptive quality of service aware middleware for replicated services
Publication TypeJournal Articles
Year of Publication2003
AuthorsKrishnamurthy S, Sanders WH, Cukier M
JournalParallel and Distributed Systems, IEEE Transactions on
Pagination1112 - 1125
Date Published2003/11//
ISBN Number1045-9219
Keywordsdistributed resource sharing, Middleware, online performance monitoring, probabilistic modeling, QoS specification, quality of service, replica consistency, replicated services, resource allocation, time-sensitive client applications, timeliness constraints

A dependable middleware should be able to adaptively share the distributed resources it manages in order to meet diverse application requirements, even when the quality of service (QoS) is degraded due to uncertain variations in load and unanticipated failures. We have addressed this issue in the context of a dependable middleware that adaptively manages replicated servers to deliver a timely and consistent response to time-sensitive client applications. These applications have specific temporal and consistency requirements, and can tolerate a certain degree of relaxed consistency in exchange for better response time. We propose a flexible QoS model that allows clients to specify their timeliness and consistency constraints. We also propose an adaptive framework that dynamically selects replicas to service a client's request based on the prediction made by probabilistic models. These models use the feedback from online performance monitoring of the replicas to provide probabilistic guarantees for meeting a client's QoS specification. The experimental results we have obtained demonstrate the role of feedback and the efficacy of simple analytical models for adaptively sharing the available replicas among the users under different workload scenarios.