Cost‐aware execution of transactional web services using labelled transition systems

Abstract

Recently web service composition has become a very cost-effective way to develop business applications. However, owing to the unreliable nature of web services, providing the transactional support in execution of a service composition is an important design requirement. To guarantee the transactional execution of service compositions, a fault-handling routine has to be started once a service failure occurs in order to undo the effect of previously completed services by calling their corresponding compensation operations. Currently this fault-handling mechanism is implemented by means of low-level programming constructs such as exception-handling mechanism in languages such as WS-BPEL. However, since the logic of handling service failures might become very complex in some applications, this concern should be separated from the normal flow of the composition workflow based on the separation of concerns principle. To achieve this, in this study we have proposed an orchestration pattern for building a transactional service composition in which the failure-recovery logic is imposed on the composition workflow by a Labelled Transition System (LTS) as a separate module. It is assumed that each service within the composition is associated with two known transactional properties: (i) a rollback cost that indicates the cost of undoing (compensating) the service and (ii) a failure probability. The transactional logic of the service composition is also specified using the rollback dependencies represented in a rollback graph. An LTS then is generated to schedule the execution of services within the composition based on the composition transactional logic and properties such that upon a service failure, a recovery path with the lowest cost is followed.

A pessimistic method in web service composition by view on execution states

“…Boushehrian and Zare have proposed a system to build transactional compositions with low rollback cost using a tagging system and a scheduler. 25 In the method, by using virtual dependencies, primacy and recency were created between parallel web services. Both primacy and recency remove rollback cost of some web services, which in turn significantly decreases average rollback cost.…”

“…Boushehrian and Zare have proposed a system to build transactional compositions with low rollback cost using a tagging system and a scheduler . In the method, by using virtual dependencies, primacy and recency were created between parallel web services.…”

Dependable composition of transactional web services using fault‐tolerance patterns and service scheduling

“…The choice between the forward or backward recovery upon a service failure can be made either at run time based on the context information but by incurring some runtime overhead [12, 13] or at design time using an optimisation algorithm [5, 14, 6, 10, 2].…”

“…Composing basic services in composition tools to obtain a value‐added service which can be deployed and executed by the execution engines is widely used by software developers. In the unreliable Internet infrastructure the concept of Transactional Service Composition (TSC) is recently known as an important non‐functional concern when designing safe and reliable service compositions [1–3]. A composite service with the transactional property guarantees the atomic execution, i.e.…”

“…A more general transactional model for the service composition has been proposed in our previous studies [6, 2] in which a rollback dependency was used to define the transactional requirements of a composite service. According to this new dependency type (along with the conventional data and control dependencies), task t i in the composition workflow is rollback dependent on the task t j when the compensation (or rollback) of t i has to be started upon the failure of task t j .…”