Composite Systems : Decentralized Nested Transactions

This thesis deals with how to define and build correct distributed nested transactions in a completely decentralized way. In particular, it studies nested transactions in a distributed system of arbitrarily interconnected independent components, with only local knowledge in each component and local rules to enforce correctness. Such systems are called composite systems, and the corresponding transactions are composite transactions. Invocations of remote servers are automatically treated as subtransactions of the issuing transaction, improving both fault-tolerance and response times. Open transaction models are supported, in order to release resources as soon as possible. Correctness of composite transactions is defined, and some correct and minimal protocols are proposed. The theoretical framework also applies to existing distributed transaction models and identifies their problems. By proposing a more powerful transaction model, namely the more general composite transactions, these problems can be solved. On the practical side, this work presents the CheeTah prototype, a black-box framework written entirely in Java, for light-weight composite transaction management. It implements all the protocols that were presented in the theoretical discussion, and shows that they are feasible in practice.