A Middleware for Reflective Web Service Choreographies on the Cloud


Web service composition is a commonly used solution to build distributed systems on the cloud. Choreographies are one specific kind of service composition in which the responsibilities for the execution of the system are shared by its service components without a central point of coordination. Due to the distributed nature of these systems, a manual approach to resource usage monitoring and allocation to maintain the expected Quality of Service (QoS) is not only inefficient but also does not scale. In this paper, we present an open source choreography enactment middleware that is capable of automatically deploying and executing a composition. Additionally, it also monitors the composition execution to perform automatic resource provisioning and dynamic service reconfiguration based on pre-defined Service Level Agreement (SLA) constraints. To achieve that, it keeps a meta-level representation of the compositions, which contains their specifications, deployment statuses, and QoS attributes. Application developers can write specific rules that take into account these meta-data to reason about the performance of the composition and change its behavior. Our middleware was evaluated on Amazon EC2 and our results demonstrate that, with little effort from the choreography developer or deployer, the middleware is able to maintain the established SLA using both horizontal and vertical scaling when faced with varying levels of load. Additionally, it also reduces operational costs by using as little computational resources as possible.

Proceedings of the 13th Workshop on Adaptive and Reflective Middleware (ARM2014), In conjunction with ACM/IFIP/USENIX ACM International Middleware Conference.