A Provider-Agnostic Approach to Multi-cloud Orchestration Using a Constraint Language

Cloud computing and its computing as an utility paradigm provides on-demand resources allowing the seamless adaptation of applications to fluctuating demands. While the Cloud's ongoing commercialisation has lead to a vast provider landscape, vendor lock-in is still a major hindrance. Recent outages demonstrate that relying exclusively on one provider is not sufficient. While existing cloud orchestration tools promise to solve the problems by supporting deployments across multiple cloud providers, they typically rely on provider dependent models forcing prior knowledge of offers and obstructing flexibility in case of errors. We propose a cloud provider-agnostic application and resource description using a constraint language. It allows users to express resource requirements of an application without prior knowledge of existing offers. Additionally, we propose a discovery service automatically collecting available offers. We combine this with a matchmaking algorithm representing the discovery model and the user-given constraints in a constraint satisfaction problem (CSP) that is then solved. Finally, we manipulate this discovery model during runtime to react on errors. Our evaluation shows that using a constraint-based language is a feasible approach to the provider selection problem, and that it helps to overcome vendor lock-in.