Elastically Ruling the Cloud: Specifying Application's Behavior in Federated Clouds

Most Infrastructure as a Service clouds present limited capabilities to control how a service behaves at runtime, once it has been deployed, beyond basic low-level scalability rules for VMs. Higher-level approaches fail to provide mechanisms for a fine grained level of control of the service at runtime, being only focused on scaling. These scalability rules are based on an ad hoc ``grammar'' that is not expressive enough to reflect other desired control mechanisms at runtime (e.g. reconfigurations, dynamic changes in the rules or in the components of the application, retiering, etc.). Here, we present an analysis on different alternatives for supporting such features. The Rule Interchange Format (RIF) emerges as a likely candidate to support the required flexibility and so it is proved in a typical use case. Also, a preliminary implementation of a mapping mechanisms is offered to parse RIF rules to widespread rule engines such as Drools and Jess.