Towards portability and interoperability support in middleware for hybrid clouds

The cloud computing paradigm promises increased flexibility and scalability for consumers and providers of software services. Service providers that exploit private cloud environments offer restricted flexibility and scalability because of the limited capacity. However, such organizations are often reluctant to migrate to public clouds because of business continuity threats and vendor lock-in. Hybrid clouds potentially combine the benefits of private and public (external) clouds. Vendor lock-in can be avoided when multiple external clouds are supported and effectively exploited. This paper presents a middleware platform for hybrid cloud applications. The middleware enables organizations to control the execution of their applications in hybrid cloud environments. Driven by policies, the middleware can dynamically decide which requests and tasks are executed on a particular part of the hybrid cloud. The core of the middleware, and the focus of this paper, is an abstraction layer. The abstraction layer enables portability over multiple services including data storage, blob storage, and asynchronous task execution of various PaaS platforms as well as interoperability between the PaaS platforms. We have validated the core concept by building a prototype implementation that runs on top of specific PaaS platforms as well as on a cloud-enabling middleware. A document processing SaaS application has been instantiated on the middleware. Performance results have been collected for JBoss AS cluster, Google App Engine, and Red Hat OpenShift.