An architecture for highly available wide-area service composition

Service composition provides a flexible way to quickly enable new application functionalities in next generation networks. We focus on the scenario where next generation portal providers 'compose' the component services of other providers. We have developed an architecture based on an overlay network of service clusters to provide failure-resilient composition of services across the wide-area Internet: our algorithms detect and recover quickly from failures in composed client sessions. In this paper, we present an evaluation of our architecture whose overarching goal is quick recovery of client sessions. The evaluation of an Internet-scale system like ours is challenging. Simulations do not capture true workload conditions and Internet-wide deployments are often infeasible. We have developed an emulation platform for our evaluation-one that allows a realistic and controlled design study. Our experiments show that the control overhead involved in implementing our recovery mechanism is minimal in terms of network as well as processor resources; minimal additional provisioning is required for this. Failure recovery can be effected using alternate service replicas within about I s after failure detection on Internet paths. We collect trace data to show that failure detection itself can be tight on wide-area Internet paths-within about 1.8 s. Failure detection and recovery within these time bounds represents a significant improvement over existing Internet path recovery mechanisms that take several tens of seconds to a few minutes. (C) 2003 Elsevier B.V. All rights reserved.