Automating the support of highly-configurable services

Faltan las palabras claveLas crecientes capacidades de configuración de los servicios, especialmente en el cloud, han dado lugar a los así llamados Servicios Altamente Configurables (HCSs). Dichas capacidades de configuración están aumentando la demanda y complejidad de las aplicaciones basadas en HCS y de las necesidades de infraestructura para soportarlas, soluciones guiadas por HCS de aquí en adelante. Tras un estudio del estado del arte, concluimos que dichas soluciones guiadas por HCSs pueden ser mejoradas significativamente en 1) los lenguajes para describir las configuraciones, también conocidas como el espacio de decisión del servicio, y 2) en las técnicas para extraer información de utilidad del espacio de decisión, técnicas de análisis en adelante. Por un lado, no existen Lenguajes Específicos de Dominio (DSLs) para describir el espacio de decisión, aunque hay algunas aproximaciones cercanas. En esta tesis creemos que es posible mejorar el actual panorama diseñando un DSL: i) en conformidad con los principales proveedores de HCSs, ii) que soporte múltiples ítems, iii) suficientemente expresivo para facilitar la descripción de relaciones lógicas y aritméticas en los términos del servicio y iv) independiente del dominio. Adicionalmente, este DSL debe definir criterios de validez para asegurar que el espacio de decisión satisface propiedades básicas como la consistencia y la configurabilidad. Más allá, se deben ofrecer explicaciones cuando el espacio de decisión del servicio no satisfaga dichas propiedades. Por otro lado, la mayor parte de las actuales técnicas de análisis, como aquellas encargadas de encontrar configuraciones óptimas o de reconfigurar servicios multitenant, llevan consigo algunos inconvenientes propios de técnicas emergentes. Para superar estos inconvenientes, se deben desarrollar: a) implementaciones de referencia totalmente funcionales, b) técnicas reusables, c) mecanismos de extensión efectivos e d) interfaces amigables. El principal objetivo de esta disertación es mejorar el soporte existente para el desarrollo de soluciones guiadas por HCS, considerando las recomendaciones anteriores. Las principales contribuciones de esta tesis son un DSL (llamado SYNOPSIS) para especificar el espacio de decisión de los HCS, y un nuevo catálogo de operaciones para comprobar y explicar los criterios de validez así como para encontrar configuraciones óptimas para uno o más usuarios. Como contribuciones menores, también presentamos dos soluciones que han sido desarrolladas para mejorar el soporte existente para la migración de infraestructuras a Amazon EC2 y para reconfigurar servicios multitenant. La piedra angular de nuestra propuesta para mejorar las técnicas de especificación ha sido definir un DSL, SYNOPSIS, y dotarlo con semántica formal basada en Modelos de Características con Estados. Acerca de nuestra propuesta para mejorar las técnicas de análisis, la clave ha sido la organización de dichas técnicas en un catálogo de operaciones básicas que pueden ser combinadas para dar lugar a soluciones guiadas por HCS m más avanzadas. La aplicabilidad de nuestros resultados está limitada a aquellos espacios de decisión que pueden ser transformados en Modelos de Características con Estados, que por nuestra experiencia es suficiente para soportar HCSs reales.The growing customisation capabilities of services, especially in Cloud scenarios, have led to the so-named Highly-configurable Services (HCSs). Such capabilities are boosting the demand and complexity of HCS-based applications and the infrastructure need to support them, HCS-driven solutions from now on. After a study of the existing literature we conclude that these HCS-driven solutions can be significantly enhanced in both 1) the languages to describe the configurations, a.k.a. the decision space of HCSs and 2) the techniques to extract useful information from the decision space, analysis techniques, in advance. On the one hand, there are no Domain Specific Languages (DSLs) to describe the decision space, although there exist some very close approaches. We suggest that it is possible to improve the current landscape by designing a DSL: i) Compliant with big HCS vendors, ii) multi-item aware, iii) expressive-enough to ease the description of arithmetic-logical relationships on configurable description terms, and iv) domainindependent. In addition, this DSL must define validity criteria for checking that the decision space satisfies some basic properties such as the consistency, and the configurability. Furthermore, explanations must be provided when the decision space do not satisfy such basic properties. On the other hand, most of the current analysis techniques such as those relate to find optimal configurations or reconfigure a multi-tenant service includes some drawbacks that can be found in emerging techniques. To overcome such drawbacks there must be developed: a) fully-functional reference implementations, b) techniques with a reuse-oriented design, c) effective extension mechanisms, and d) user-friendly interfaces. The main goal of this dissertation is to enhance the existing support to develop HCS-driven solutions considering the aforementioned suggestions for improvement. The main thesis contributions are a DSL to specify the decision space of HCSs called SYNOPSIS, and a novel catalogue of analysis operations to check and explain validity criteria as well as to find optimal configurations for one or many users. As minor contributions, two solutions have been developed to improve the existing tooling support to migrate on-premise infrastructure to Amazon EC2 and to reconfigure multi-tenant service. The cornerstone of our proposal to improve the specification techniques has been to define a DSL, SYNOPSIS, and endow it with a formal semantics based on Stateful Feature Models. Regarding our proposal to improve the analysis techniques, the key has been the organization of such techniques in a catalogue of basic analysis operations that can be combined to support more advanced HCS-driven solutions. The applicability of our results is limited to those decision spaces that can be translated to a Stateful Feature Model, that is enough to support real-world HCSs, in our experience

BETTY: Benchmarking and Testing on the Automated Analysis of Feature Models

The automated analysis of feature models is a flourishing research topic that has called the attention of both researchers and practitioners during the last two decades. During this time, the number of tools and techniques enabling the analysis of feature models has increased and also their complexity. in this scenario, the lack of specific testing mechanisms to assess the correctness and good performance of analysis tools is becoming a major obstacle hindering the development of tools and affecting their quality and reliability. in this paper, we present BeTTy, a framework for BEnchmarking and TesTing on the analY sis of feature models. Among other features, BeTTy enables the automated detection of faults in feature model analysis tools. Also, it supports the generation of motivating test data to evaluate the performance of analysis tools in both average and pessimistic cases. Part of the functionality of the framework is provided through a web-based interface facilitating the random generation of both classic and attributed feature models

ISA PACKAGER: a Tool for SPL Deployment

In software projects, and particularly in Software Product Line (SPL) projects, product composition and deployment are tasks that are not supported by open source tools. These tasks are repetitive and error-prone. Automation helps on reducing the errors while the productivity increases. in this paper we present a real-world experience through ISA Packager, a generic tool to package and deploy SPLs. in this experience we build a SPL of SCADAs (Supervisory Control and Data Acquisition). Each customized SCADA product evolves in time and ISA Packager is in charge of easing product maintenance and updating

Multi-User Variability Configuration: a Game Theoretic Approach

Multi-user configuration is a neglected problem in variability-intensive systems area. The appearance of conflicts among user configurations is a main concern. Current approaches focus on avoiding such conflicts, applying the mutual exclusion principle. However, this perspective has a negative impact on users satisfaction, who cannot make any decision fairly. in this work, we propose an interpretation of multi-user configuration as a game theoretic problem. Game theory is a well-known discipline which analyzes conflicts and cooperation among intelligent rational decisionmakers. We present a taxonomy of multi-user configuration approaches, and how they can be interpreted as different problems of game theory. We focus on cooperative game theory to propose and automate a tradeoff-based bargaining approach, as a way to solve the conflicts and maximize user satisfaction at the same time

Start-up of a microalgae-based treatment system within the biorefinery concept: from wastewater to bioproducts

©IWA Publishing [2018]. The definitive peer-reviewed and edited version of this article is published in Water Science & Technology, volume 78, issue 1, p. 114-124, 2018, doi: 10.2166/wst.2018.195 and is available at www.iwapublishing.com.Within the European project INCOVER, an experimental microalgae-based treatment system has been built for wastewater reuse and added-value products generation. This article describes this new experimental plant and the start-up stage, starting from the new design of three semi-closed horizontal photobioreactor (PBR) with low energy requirements for microalgae cultivation (30 m3 total), using agricultural runoff and urban wastewater as feedstock. The inflow nutrients concentration is adjusted to select cyanobacteria, microalgae able to accumulate polyhydroxybutyrates (PHBs), which can be used for bioplastics production. Part of the harvested biomass is used as substrate for anaerobic co-digestion (AcoD) with secondary sludge to obtain biogas. This biogas is then cleaned in an absorption column to reach methane concentration up to 99%. The digestate from the AcoD is further processed in sludge wetlands for stabilization and biofertilizer production. On the other hand, treated water undergoes ultrafiltration and disinfection through a solar-driven process, then it is pumped through absorption materials to recover nutrients, and eventually applied in an agricultural field to grow energy crops by means of a smart irrigation system. This plant presents a sustainable approach for wastewater management, which can be seen as resource recovery process more than a waste treatment.Peer ReviewedPostprint (author's final draft

FaMa Abductive: una herramienta para explicaciones de errores en modelos de características

La diagnosis de errores es una asignatura pendiente de gran parte de las herramientas de an´alisis de modelos de caracter´ısticas. Realizar este proceso manualmente no es viable con modelos de tama˜no medio/grande, e incluso tampoco para modelos peque˜nos, pues la mayor´ıa de errores son extremadamente dif´ıciles de detectar y m´as a´un de explicar. En esta demo presentamos FaMa Abductive, una extensi´on de la herramienta FaMa, encargada de la diagnosis autom´atica en modelos de caracter´ısticas. Esta herramienta provee detecci´on y explicaciones para errores en modelos de caracter´ısticas, tanto b´asicos como extendidos, y tambi´en para productos err´oneos en modelos de caracter´ısticas b´asicos

Cultivation and selection of cyanobacteria in a closed photobioreactor used for secondary effluent and digestate treatment

“The final publication is available at Springer via http://dx.doi.org/10.1016/j.scitotenv.2017.02.097"The main objective of this study was to select and grow wastewater-borne cyanobacteria in a closed photobioreactor (PBR) inoculated with a mixed consortium of microalgae. The 30 L PBR was fed with a mixture of urban secondary effluent and digestate, and operated in semi-continuous mode. Based on the nutrients variation of the influent, three different periods were distinguished during one year of operation. Results showed that total inorganic nitrogen (TIN), inorganic phosphorus concentration (PO43 -), phosphorus volumetric load (LV-P) and carbon limited/non-limited conditions leaded to different species composition, nutrients removal and biomass production in the culture. High TIN/PO43 - concentrations in the influent (36 mg N L- 1/3 mg P L- 1), carbon limitation and an average LV-P of 0.35 mg P L- 1d- 1 were negatively related to cyanobacteria dominance and nutrients removal. On the contrary, cyanobacteria predominance over green algae and the highest microbial biomass production (averaging 0.084 g Volatile Suspended Solids (VSS) L- 1d- 1) were reached under TIN/PO43 - concentrations of 21 mg N L- 1/2 mg P L- 1, no carbon limitation and an average LV-P of 0.23 mg P-PO43 - L- 1d- 1. However, although cyanobacteria predominance was also favored with a LV-P 0.15 mg L- 1d- 1, biomass production was negatively affected due to a P limitation in the culture, resulting in a biomass production of 0.0.39 g VSS L- 1d- 1. This study shows that the dominance of cyanobacteria in a microalgal cyanobacterial community in an agitated PBR using wastewater as nutrient source can be obtained and maintained for 234 days. These data can also be applied in future biotechnology applications to optimize and enhance the production of added value products by cyanobacteria in wastewater treatment systems.Peer ReviewedPostprint (author's final draft

Configurable Feature Models

Feature models represent all the products that can be built under a variability-intensive system such as a software product line, but they are not fully configurable. There exist no explicit effort in defining configuration models that enable making decisions on attributes and cardinalities in feature models that use these artefacts. In this paper we present configurable feature models as an evolution from feature models that integrate configuration models within, improving the configurability of variability-intensive systems

Production of polyhydroxybutyrates and carbohydrates in a mixed cyanobacterial culture : effect of nutrients limitation and photoperiods

In the present study, different photoperiods and nutritional conditions were applied to a mixed wastewater-borne cyanobacterial culture in order to enhance the intracellular accumulation of polyhydroxybutyrates (PHBs) and carbohydrates. Two different experimental set-ups were used. In the first, the culture was permanently exposed to illumination, while in the second, it was submitted to light/dark alternation (12h cycles). In both cases, two different nutritional regimes were also evaluated, N-limitation and P-limitation. Results showed that the highest PHB concentration (104 mg L-1) was achieved under P limited conditions and permanent illumination, whereas the highest carbohydrate concentration (838 mg L-1) was obtained under N limited condition and light/dark alternation. With regard to bioplastics and biofuel generation, this study demonstrates that the accumulation of PHBs (bioplastics) and carbohydrates (potential biofuel substrate) is favored in wastewater-borne cyanobacteria under conditions where nutrients are limited.Peer ReviewedPostprint (published version

Automating the deployment of componentized systems

Embedded and self-adaptive systems demand continuous adap- tation and reconfiguration activities based on changing quality condi- tions and context information. As a consequence, systems have to be (re)deployed several times and software components need to be mapped onto new or existing hardware pieces. Today, the way to determine an optimal deployment in complex systems, often performed at runtime, constitutes a well-known challenge. In this paper we highlight the major problems of automatic deployment and present a research plan to reach for an UML-based solution for the deployment of componentized sys- tems. As a first step towards a solution, we use the UML superstructure to suggest a way to redeploy UML component diagrams based on the inputs and outputs required to enact an automatic deployment process.Comisión Interministerial de Ciencia y Tecnología (CICYT) SETI (TIN2009-07366