No abstract

Business Process Execution Language for Web Services (BPEL) is becoming the industrial standard for modeling web service-based business processes. Behavioral compatibility for web service composition is one of the most important topics. The commonly used reachability exploration method focuses on verifying deadlock-freeness. When this property is violated, the states and traces in the reachability graph only give clues to re-design the composition. The process must then repeat itself until no deadlock is found. In this paper, multiple web services interaction is modeled with a Petri net called Composition net (C-net for short). The problem of behavioral compatibility among web services is hence transformed into the deadlock structure problem of a C-net. If services are incompatible, a policy based on appending additional information channels is proposed. It is proved that it can offer a good solution that can be mapped back into the BPEL models automatically.

Abstract-Resource provisioning for N -tier web applications in Clouds is non-trivial due to at least two reasons. First, there is an inherent optimization conflict between cost of resources and Service Level Agreement (SLA) compliance. Second, the resource demands of the multiple tiers can be different from each other, and varying along with the time. Resources have to be allocated to multiple (virtual) containers to minimize the total amount of resources while meeting the end-to-end performance requirements for the application. In this paper we address these two challenges through the combination of the resource controllers on both application and container levels. On the application level, a decision maker (i.e., an adaptive feedback controller) determines the total budget of the resources that are required for the application to meet SLA requirements as the workload varies. On the container level, a second controller partitions the total resource budget among the components of the applications to optimize the application performance (i.e., to minimize the round trip time). We evaluated our method with three different workload models-open, closed, and semiopen-that were implemented in the RUBiS web application benchmark. Our evaluation indicates two major advantages of our method in comparison to previous approaches. First, fewer resources are provisioned to the applications to achieve the same performance. Second, our approach is robust enough to address various types of workloads with time-varying resource demand without reconfiguration.