Client - centered Load Distribution : A Mechanism for

نویسندگان

  • Vittorio Ghini
  • Fabio Panzieri
  • Marco Roccetti
چکیده

The success of a Web service is largely dependent on its responsiveness (i.e., its availability and timeliness) in the delivery of the information its users (clients) require. A practical approach to the provision of responsive Web services, recently proposed in the literature [7], is based on introducing redundancy in the service implementation, namely by replicating the service across a number of servers geographically distributed over the Internet; provided that the replica servers be maintained mutually consistent, service responsiveness can be guaranteed by dynamically binding the client to the "most convenient" replica (e.g., the nearest, lightly loaded, available replica, the available replica with the least congested connection with the client). Based on this approach, we have developed a software mechanism that meets effectively the responsiveness requirement mentioned above. In essence, this mechanism, rather than binding a client to its most convenient replica server, engages all the available replicas in supplying a fragment of the Web document that client requires. The size of the fragment a replica is requested to supply is dynamically evaluated on the basis of the response time that replica can provide its client with. In addition, the proposed mechanism can dynamically adapt to changes in both the network and the replica servers status, thus tolerating possible replica or communication failures that may occur at run-time. In this paper, we describe the design, the implementation, and an experimental validation of that mechanism. The performance results we have obtained from our validation excercise illustrate the adequacy of the mechanism we propose. (1) Università di Bologna, Dipartimento di Scienze dell'Informazione, Mura Anteo Zamboni 7, 40127 Bologna, Italy. E-mail: ghini, panzieri, roccetti@cs.unibo.it Client-centered Load Distribution: A Mechanism for Constructing Responsive Web Services.

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تاریخ انتشار 2000