Self-adaptation Challenges for Cloud-based Applications: A Control Theoretic Perspective

Software applications accessible over the web are typically subject to very dynamic workloads. Since cloud elasticity provides the ability to adjust the deployed environment on the fly, modern software systems tend to target cloud as a fertile deployment environment. However, relying only on native elasticity features of cloud service providers is not sufficient for modern applications. This is because current features rely on users’ knowledge for configuring the performance parameters of the elasticity mechanism and in general users cannot optimally determine such sensitive parameters. In order to overcome this user dependency, using approaches from autonomic computing is shown to be appropriate. Control theory proposes a systematic way to design feedback control loops to handle unpredictable changes at runtime for software applications. Although there are still substantial challenges to effectively utilize feedback control in self-adaptation of software systems, software engineering and control theory communities have made recent progress to consolidate their differences by identifying challenges that can be addressed cooperatively. This paper is in the same vein, but in a narrower domain given that cloud computing is a sub-domain of software engineering. It aims to highlight the challenges in the self-adaptation process of cloud-based applications in the perspective of control engineers.