Cloud services based on virtualization and automated deployment and orchestration makes it possible for SaaS providers to delegate self-adaptation of their SaaS applications/services to the Cloud provider that operates a Cloud environment where these SaaS applications or services are run. Notably, this delegation can be handled by a PaaS layer running on the top of IaaS infrastructures operated by a single or different IaaS providers. For instance, the horizontal and vertical elasticity of a Cloud environment can be exploited by PaaS at runtime to keep the cost and energy demand of operating a SaaS application to a minimum required to maintain a desired quality of service (eg such as time performance).
Although a PaaS can enact actions to scale up or down an underlying Cloud infrastructure, it does not know the exact expectations from a SaaS provider or end-users regarding quality of service, acceptable charges and eventual energy consumption behaviour requirements. Thus, for self-adaptation to meet SaaS level expectations, self-adaptation trigger conditions and in some cases, self-adaptation action responses must be specified by SaaS actors and communicated to the Cloud provider. ASCETIC explores how this can be achieved by providing self-adaptation rules in OVF manifest files.