Leader/Followers Douglas C. Schmidt, Carlos O’Ryan, Michael Kircher, Irfan Pyarali, and Frank Buschmann {schmidt, coryan}@uci.edu, {Michael.Kircher, Frank.Buschmann}@mchp.siemens.de,
[email protected] University of California at Irvine, Siemens AG, and Washington University in Saint Louis The Leader/Followers architectural pattern provides an efficient concurrency model where multiple threads take turns sharing a set of event sources in order to detect, de- multiplex, dispatch, and process service requests that occur on these event sources. Example Consider the design of a multi-tier, high-volume, on-line transaction processing (OLTP) system. In this design, front-end communication servers route transaction requests from remote clients, such as travel agents, claims processing centers, or point-of-sales terminals, to back-end database servers that process the requests transactionally. After a transaction commits, the database server returns its results to the associated communication server, which then forwards the results back to the originating remote client. This multi-tier architecture is used to improve overall system throughput and reliability via load balancing and redundancy, respectively.It LAN WAN Front-End Back-End Clients Communication Servers Database Servers also relieves back-end servers from the burden of managing different communication protocols with clients. © Douglas C. Schmidt 1998 - 2000, all rights reserved, © Siemens AG 1998 - 2000, all rights reserved 19.06.2000 lf.doc 2 Front-end communication servers are actually ``hybrid'' client/server applications that perform two primary tasks: 1 They receive requests arriving simultaneously from hundreds or thousands of remote clients over wide area communication links, such as X.25 or TCP/IP.