Decentralized Coordination of Transactional Processes in Peer-to-Peer Environments *

Abstract

Business processes executing in peer-to-peer environments usually invoke Web services on different, independent peers. Although peer-to-peer environments inherently lack global control, some business processes nevertheless require global transactional guarantees, i.e., atomicity and isolation applied at the level of processes. This paper introduces a new decentralized serialization graph testing protocol to ensure concurrency control and recovery in peer-to-peer environments. The uniqueness of the proposed protocol is that it ensures global correctness without relying on a global serializa-tion graph. Essentially, each transactional process is equipped with partial knowledge that allows the transactional processes to coordinate. Globally correct execution is achieved by communication among dependent transactional processes and the peers they have accessed. In case of failures, a combination of partial backward and forward recovery is applied. Experimental results exhibit a significant performance gain over traditional distributed locking-based protocols with respect to the execution of transactions encompassing Web service requests.