The telco industry is gradually shifting from using monolithic software packages deployed on custom hardware to using modular virtualized software functions deployed on cloudified data centers using commodity hardware. This transformation is referred to as Network Function Virtualization (NFV). The scalability of the databases (DBs) underlying the virtual network functions is the cornerstone for reaping the benefits from the NFV transformation. This paper presents an industrial experience of applying shared-nothing techniques in order to achieve the scalability of a DB in an NFV setup. The special combination of requirements in NFV DBs are not easily met with conventional execution models. Therefore, we designed a special shared-nothing architecture that is based on cooperative multi-tasking using user-level threads (fibers). We further show that the fiber-based approach outperforms the approach built using conventional multi-threading and meets the variable deployment needs of the NFV transformation. Furthermore, fibers yield a simpler-to-maintain software and enable controlling a trade-off between long-duration computations and real-time requests.

In software product lines development, it is sometimes important to provide a flexible binding time for features such that developers can choose between static or dynamic feature activation. For example, software products designed for devices with constrained resources may use a static binding time to avoid the performance overhead introduced by dynamic binding time activation. However, other devices can exploit binding time flexibility to support products with a dynamic binding time for some of their features. To implement this kind of flexibility in a modular way, we can define AspectJ-based idioms. Researchers have proposed Edicts, an idiom based on AspectJ and design patterns. In this article, we argue that this idiom leads to an increase in code duplication, scattering, tangling and size, which can hamper code reuse, maintenance and understanding. To mitigate such issues, this paper proposes three idioms based on aspect-oriented programming to implement flexible feature binding. We apply our three idioms, along with Edicts, to implement a flexible binding time for features in four different applications. By doing so, we were able to assess the resulting implementations by using software metrics that judge code-quality factors. Our evaluation suggests that our idioms reduce the above-mentioned problems when implementing flexible feature binding for the selected features.

Virtual classes allow nested classes to be refined in subclasses. In this way nested classes can be seen as dependent abstractions of the objects of the enclosing classes. Expressing dependency via nesting, however, has two limitations: Abstractions that depend on more than one object cannot be modeled and a class must know all classes that depend on its objects. This paper presents dependent classes, a generalization of virtual classes that expresses similar semantics by parameterization rather than by nesting. This increases expressivity of class variations as well as the flexibility of their modularization. Besides, dependent classes complement multimethods in scenarios where multi-dispatched abstractions rather than multi-dispatched methods are needed. They can also be used to express more precise signatures of multimethods and even extend their dispatch semantics. We present a formal semantics of dependent classes and a machine-checked type soundness proof in Isabelle/HOL [29], the first of this kind for a language with virtual classes and path-dependent types.