Looking Ahead in Open Multithreaded Transactions

Open multithreaded transactions constitute building blocks that allow a developer to design and structure the execution of complex distributed systems featuring cooperative and competitive concurrency in a reliable way. In this paper we describe an optimization to the standard open multithreaded transaction model that does not impose any participant synchronization when committing a transaction, but still provides the same execution semantics. This optimization - letting participants "look ahead" and continue their execution on the outside of the transaction - makes it possible to speed up the execution of in individual transaction with multiple participants tremendously. The paper describes all technical issues that had to be solved, e.g. adapting concurrency control of transactional objects to be look-ahead aware, adapting joining rules for lookahead participants, and re-defining exception handling in the presence of look-ahead.