Architectural principles and decision model for Function-as-a-Service

Abstract

Cloud computing revolutionized the way modern applications are designed and operated. Instead of maintaining the on premise infrastructure many enterprises incorporate various cloud offerings when designing their applications to decrease time-to-market and reduce the required management efforts. This includes the use of traditional cloud service models such as IaaS or PaaS as well as novel models such as FaaS that enables engineering cloud applications by composing fine-grained functions hosted on FaaS platforms with a variety of provider-managed services, e.g., data persistence and messaging services. Most management tasks for the components in FaaS-based applications become a responsibility of the chosen cloud provider, which, however, results in a stronger dependence on provider products and their implementation and packaging requirements. Therefore, engineering of FaaS-based applications can benefit from a stronger focus on the architectural considerations instead of specific products that often appear as fast as they become obsolete. This work focuses on different aspects of provider-agnostic design for FaaS-based applications and is inspired by the increased dependence of components in such applications on product-specific requirements. To enable reasoning on component hosting and management requirements in a provider-agnostic manner, this work introduces a pattern language capturing various trade-offs for hosting application components in the cloud. Furthermore, to facilitate classification and selection support for components in FaaS-based applications, this work presents a classification framework for FaaS platforms and introduces a classification framework metamodel that generalizes these concepts for other component types in such applications. Additionally, this work introduces a standards-based modeling approach for specifying function orchestrations and transforming them into provider-specific formats and an automated function code extraction and wrapping approach that aims to facilitate reusing functions for different FaaS platforms. To enable using these contributions together, this thesis also introduces the GRASP method that enables gradual modeling and refinement of FaaS-based applications from abstract topologies to executable deployment models. The technological support for using the GRASP Method is enabled by an integrated GRASP toolchain. To validate the feasibility of the introduced concepts, the GRASP toolchain is implemented prototypically and integrated with the existing tools for pattern-based modeling and deployment of cloud applications.