• Static policy. Developers must define a given service's server-invocation order at deployment time. The generated smart proxy will invoke the first server of this sequence; if the server fails, the proxy will invoke the next server and so on. The static policy fails when all the listed servers fail; in this case, the proxy generates an exception to the client application.
• Random policy. The proxy accesses the server randomly at invocation time. If the selected server fails, the random-selection process repeats using the remaining servers. If all servers fail, the proxy propagates an exception to the client process.
• Parallel policy. The proxy uses threads to invoke all listed servers concurrently. It returns the first reply to the client application and ignores the remaining replies. If all servers fail, the proxy raises an exception.
• Best-median policy. This policy first computes the median response time of the last k-invocations for each server. Then the proxy invokes the server with the lowest median. If this server fails, the proxy invokes the remaining servers sequentially, following the ascending order of the medians. If all servers fail, the proxy raises an exception.
• Parallel best-median policy. PBM generalizes the parallel and best-median policies, striving to combine their benefits, as we now describe in more detail.
interface name= TemperatureConverterwebserver alias= pucminas uri= http://www.inf.pucminas.br/ConvertTemp.jws?WSDL adapter= PucMinasAdapter
policy pbm(k=1.2, p=2, n=10, t=3, service1, ..., serviceN)
session begin= login end= logout
• WS1 and WS2, located at one of Brazil's largest ISPs ( http://www.terra.com.br);
• WS3 and WS4, located at a regional Brazilian ISP ( http://www.twi.com.br);
• WS5, located at a federal Brazilian university ( http://www.leopoldina.cefetmg.br); and
• WS6, located at a state Brazilian university ( http://www.ic.unicamp.br).
José Geraldo Ribeiro Jr. is an assistant professor at the Federal Center of Technological Education-Minas Gerais. His research interests include service-oriented computing, middleware, parallel programming, and operating systems. He received his master's degree in computer science from Pontifical Catholic University of Minas Gerais. Contact him at CEFET Minas, Rua Jose Peres, 558, Leopoldina, MG, Brazil, 36700-000; mailto:firstname.lastname@example.org
Glauber Tadeu do Carmo is a master's student in computer science at Federal University of Minas Gerais. His research interests include service-oriented computing and embedded systems. Contact him at PUC Minas, Unidade Sao Gabriel, Anel Rodoviario Km 23.5, Belo Horizonte, MG, Brazil, 31980-110; mailto:email@example.com
Marco Túlio Valente is an assistant professor at the Institute of Informatics at Pontifical Catholic University of Minas Gerais. His research interests include middleware, programming languages, aspect-oriented programming, and software engineering. He received his PhD in computer science from Federal University of Minas Gerais. He's a member of the Brazilian Computer Society. Contact him at PUC Minas, Unidade Sao Gabriel, Anel Rodoviario Km 23.5, Belo Horizonte, MG, Brazil, 31980-110; mailto:firstname.lastname@example.org.
Nabor C. Mendonça is a titular professor at the Center of Technological Sciences, University of Fortaleza. His research interests include distributed systems, service-oriented development, aspect-oriented programming, and software maintenance and reengineering. He received his PhD in computing from Imperial College London. He's a member of the IEEE Computer Society and the Brazilian Computer Society. Contact him at UNIFOR, Av. Washington Soares, 1321, Fortaleza, CE, Brazil, 60811-905; mailto:email@example.com">firstname.lastname@example.org.