The Research On The Compensation Mechanism Of Long-Running Transactions For Web Services

With the rapid development of network technology, there is an urgent that needs to achieve a loosely-coupled, language-independent, cross-platform heterogeneous application integration and interaction mechanism. Web service supports the interaction among the interoperable machines on the network as a fast-growing emerging technology, usually involving the coordination and interaction among multiple services, and dealing with failures or exceptions timely that may occur at any time in the long-running transactions. Such processes must ensure the reliability and the consistency of the running results for multiple services. These make it differ from the traditional ACID transactions, can not lock resources during the execution, and the simple rollback mechanism can not undo the impact of the completed actions. Therefore, the processing environment for Web service requires the support of the processing technology on transactions. The transaction is an effective means to tolerate failures and increase the reliability of the system. Transactions can hide the complexity of the coordination process, exception handling and recover details, as well as ease the burden on the programming staff, ignoring the complexities of the underlying activities. Thus, the transaction technologies get the broad applications and the depth research in distributed environments. Meanwhile, transactions on Web service adapt to the open network, loosely-coupled environment, facing the new challenges in the reliability and consistency of systems. Therefore, the study has the important scientific significance and the applied value. The compensation of Web transactions is used to eliminate the impacts of the submitted transactions, namely, it can activate the operation of compensating procedures. Compensation is the key whether the entire business transaction can be executed successfully. This procedure can eliminate the impacts of the submitted transactions at utmost. Therefore, we analyze the existing compensation mechanism on the problem arising easily of compensation and termination for long-running transactions, extend the processing mechanism and give the application for business transactions on the basis of StAC (Structured Activity Compensation), including the improved compensation operators and their operational semantics. Then, we give the application of the compensating business transactions-the mapping function, proving the expressiveness of StAC and providing a formal semantics for BPEL.In this thesis, we study on the compensation mechanism and their application of long-running transactions. The major contributions are as follows:Given the problem about compensation and termination of business transactions with the implementation, an extended mechanism for transactions compensation is proposed based on the structured activities compensation, including the forcibly compensation operator, dynamically updated compensation operator and isolation scope, which is effective to ensure the compensation processes run successfully. Furthermore, we illustrate the feasibility of the extended compensation semantics with a classic order example of business transactions.The labeled transition relation and the structured congruence relation are extended, meanwhile, the predicate of compensation updating is proposed, which improve the operational semantics of compensation mechanism for long-running transactions, making Web services transactions running smoothly, laying the foundation for the extensive application of business transactions.We study an application in BPEL of the structured compensation transactions in details. An abstract syntax of a subset on BPEL is proposed. Meanwhile, a mapping transition function T is defined, which can achieve the corresponding relations between BPEL and StAC, providing a formal semantics for BPEL and proving the expressiveness of StAC.