A Fault-Tolerant Scheme for Complex Transaction Patterns in J2EE

End-to-end reliability is an important issue in building large-scale distributed enterprise applications based on multi-tier architecture, but the support of reliability as adopted in conventional replication or transactions mechanisms is not enough due to their distinct objectives - replication guarantees the liveness of computational operations by using forward error recovery, while transactions guarantee the safety of application data by using backward error recovery. Combining the two mechanisms for stronger reliability is a challenging task Current solutions, however, are typically on the assumption of simple transaction pattern where a request from a single client executes in the context of exactly one transaction at the middle-tier application server, and seldom think about some complex patterns, such as client transaction enclosing multiple client requests or nested transactions. In this paper, we first identify four transaction pattern classes, and then propose a fault-tolerant scheme that can uniformly provide exactly-once semantic reliability support for these patterns. In this scheme, application servers are passively replicated to endow business logics with high reliability and high availability. In addition, by replicating transaction coordinator, the blocking problem of 2PC protocol during distributed transactions processing is eliminated. We have implemented this approach and integrated it into our own J2EE application server, OnceAS. Also, its effectiveness is discussed in different transaction patterns and the corresponding performance is evaluated