FOX: Cost-Awareness for Autonomic Resource Management in Public Clouds

Nowadays, to keep track with the fast changing requirements of internet applications, auto-scaling is an essential mechanism for adapting the number of provisioned resources to the resource demand. In the context of public clouds, there exist different natures of cost-models for charging resources. However, the accounted resource units and charged resource units may differ significantly due to the applied cost model. This can lead to a significant increase of charged costs when using an auto-scaler as it tries to match the demand of the application as close as possible. In the literature, several auto-scalers exist that support cost-aware scaling decisions but they introduce inherent drawbacks. In this work, this lack of existing cost-aware mechanisms is addressed by introducing a mediator between an application and the auto-scaler. This cost-aware mechanism is called FOX. It leverages knowledge of the charging model of the public cloud and reviews the scaling decisions found by the auto-scaler to reduce the charged costs to a minimum. More precisely, FOX delays or omits releases of resources to avoid additional charging costs if the resource is required in the future. Hereby, FOX is not restricted to use one specific auto-scaler but offers interfaces to use any auto-scaler. For an evalation under controlled conditions, FOX scales a multi-tier application deployed in a private cloud that is stressed with two real world workloads: BibSonomy and IBM CICS. As FOX provides an interface for auto-scalers, we evaluate the cost-aware mechanism with three state of the art auto-scalers: React, Adapt, and Reg. The experiments show that FOX is able to reduce the charged costs by 34% at maximum for the Amazon EC2 charging model. According to the cost model, FOX provisions more resources than required. This results in a decreased SLO violation rate from 28% to 2% at maximum. The accounted instance time increases at max. by 30%.