Controlling the Elasticity of Web Applications on Cloud Computing - Extended Version

Web applications are often exposed to unpredictable work-loads, which makes computing resource management di-cult. The resource may be overused when the workload is high and underused when the workload is low. A solution to deal with unpredictable workloads is to migrate Web applications to cloud computing infrastructures, where the resource is varied according to demand, i. e., elasticity. With elasticity, all the resource variations happen during the Web application runtime. To deal with this, the Web application , and its service layers must behave in an elastic manner , which comprises adaptation tasks. These tasks may introduce functional and non-functional errors into the Web application. To nd these errors, we must test the Web application when the adaptation tasks are performed, during the resource variations. Some tests may require a specic sequence of resource variations, which are dicult to be achieved without controllability. Therefore, in this paper, we propose an approach that controls the required resource variations. We validated our approach by conducting several experiments on Amazon EC2 cloud infrastructures. In these experiments, we successfully lead the Web application through the required resource variations

A survey on elasticity management in PaaS systems

[EN] Elasticity is a goal of cloud computing. An elastic system should manage in an autonomic way its resources, being adaptive to dynamic workloads, allocating additional resources when workload is increased and deallocating resources when workload decreases. PaaS providers should manage resources of customer applications with the aim of converting those applications into elastic services. This survey identifies the requirements that such management imposes on a PaaS provider: autonomy, scalability, adaptivity, SLA awareness, composability and upgradeability. This document delves into the variety of mechanisms that have been proposed to deal with all those requirements. Although there are multiple approaches to address those concerns, providers main goal is maximisation of profits. This compels providers to look for balancing two opposed goals: maximising quality of service and minimising costs. Because of this, there are still several aspects that deserve additional research for finding optimal adaptability strategies. Those open issues are also discussed.This work has been partially supported by EU FEDER and Spanish MINECO under research Grant TIN2012-37719-C03-01.Muñoz-Escoí, FD.; Bernabeu Aubán, JM. (2017). A survey on elasticity management in PaaS systems. Computing. 99(7):617-656. https://doi.org/10.1007/s00607-016-0507-8S617656997Ajmani S (2004) Automatic software upgrades for distributed systems. PhD thesis, Department of Electrical and Computer Science, Massachusetts Institute of Technology, USAAjmani S, Liskov B, Shrira L (2006) Modular software upgrades for distributed systems. In: 20th European Conference on Object-Oriented Programming (ECOOP), Nantes, France, pp 452–476Alhamad M, Dillon TS, Chang E (2010) Conceptual SLA framework for cloud computing. 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Diseño de una arquitectura dinámica para Set-Top Box multi proveedor de servicios

El ecosistema de servicios digitales disponibles para los dispositivos domésticos ha estado creciendo durante los últimos años. Ese crecimiento no solo es causado por el aumento significativo de los contenidos digitales disponibles, sino también por el aumento de los dispositivos conectados a Internet que son capaces de consumir estos contenidos. La mayoría de estos dispositivos suelen ser dispositivos móviles y otros dispositivos personales de consumo los cuales se están convirtiendo en los clientes preferidos. Actualmente, la mayoría de los servicios dirigidos a dispositivos heterogéneos son servicios Over-the-top (OTT). Estos servicios OTT permiten que varios dispositivos consuman el mismo contenido, ya que no hay necesidad de una infraestructura de servicio subyacente. Sin embargo, estos servicios funcionarían mejor utilizando una infraestructura dedicada que proporciona una mayor experiencia de usuario mientras que requiere menos recursos. Tomando en cuenta este panorama se puede pensar en un futuro escenario caracterizado por una gran diversidad de dispositivos, de usuarios potenciales y un gran número de servicios disponibles por lo que sería conveniente disponer de infraestructuras fiables y robustas y además poder dar soporte a cualquier tipo de servicio. Dado que la infraestructura física puede ser costosa de implementar, lo más lógico sería considerar que este ecosistema de servicios digitales va a requerir el uso de infraestructuras dinámicas y escalables. Afortunadamente, el paradigma del Cloud Computing, y sus alternativas como el Edge Computing y el Fog Computing, permiten crear instancias dinámicas de servicios y elementos de red haciendo frente a los requisitos antes mencionados mientras reduce los costes de inversión y operación. Sin embargo, el paradigma de cloud computing tiene varios problemas que requieren especial atención como: Data Lock-In (o bloqueo de proveedor) y la interoperabilidad entre proveedores de infraestructura. Hoy en día, los orquestadores de computación en la nube son bastante heterogéneos y carecen de interfaces estándar que permitan realizar despliegues automatizados. Por lo tanto, una definición de infraestructura diseñada para un proveedor de infraestructura en la nube determinado es más que probable que no se pueda crear una instancia en otros. Por lo tanto, se requieren mecanismos de configuración flexibles, administración avanzada, procesamiento descentralizado y auto-organización. En esta tesis, los autores proponen una arquitectura que amplía las funciones de red definidas en las especificaciones y estándares de NFV para incorporar funcionalidades de mayor nivel. El objetivo es ampliar la virtualización de las funciones de red con la creación de instancias de servicios en dispositivos de consumo. Los autores proponen ampliar la idea de NFV en lugar de proponer un nuevo diseño porque NFV tiene una gran aceptación en la industria y por eso contribuiremos ampliando la arquitectura NFV. De esta manera, los proveedores de servicios tendrán un control adicional del software del sistema al mover algunos servicios, tradicionalmente ubicados en los dispositivos, a la nube. Uno de los mayores problemas encontrados para extender la idea al mayor número de infraestructuras se debe a las particularidades de cada una de ellas que las hacen diferentes. Para superar esto, proponemos un modelo estructurado de información para declarar componentes, conexiones y configuraciones, que permite a la solución de arquitectura propuesta en la tesis crear instancias de un determinado conjunto de servicios en diferentes proveedores de infraestructuras en la nube. Para que esta configuración pueda ser aplicada a varios niveles en las infraestructuras, este trabajo propone utilizar un modelo segmentado por capas de software. Por lo tanto, los orquestadores pueden implementar e interconectar partes de software de una manera sencilla, independientemente del proveedor del entorno. En esta tesis se propone un modelo arquitectónico que permite construir un ecosistema virtual en entornos domésticos que requieren muchas y complejas tareas de configuración. El uso de mecanismos automáticos de gestión de software garantiza la correcta configuración y despliegue de servicios en diferentes plataformas acelerando el proceso y reduciendo la probabilidad de cometer errores de configuración. A continuación se presentan las principales contribuciones en este contexto: Diseño de un ecosistema digital doméstico e integrado. Modelo de arquitectura flexible y adaptable. Automatización en la configuración de infraestructuras y despliegue de servicios. Optimización de dependencias y del despliegue de servicios software. Modelado de la información del software de infraestructura. Orquestación del software basado en herramientas de la IaC. En resumen, el trabajo presentado en esta tesis contribuye a avanzar en el desarrollo de los ecosistemas domésticos digitales con el objetivo de proporcionar a los proveedores de servicios nuevas herramientas que les haga más fácil la gestión de los sistemas a un precio más bajo. Los consumidores de los servicios podrán gestionar de manera sencilla ecosistemas digitales donde la frontera entre lo virtual, los servicios contratados y sus dispositivos domésticos y móviles forman un todo integrado y perfectamente orquestado.Parte del contenido se desarrolló como línea de investigación en varios proyectos de I+D, denominados: - RAUDOS2 Red Interactiva Multiplataforma de Distribución de Contenidos Audiovisuales (TSI-020302-2010-67) (Proy. Nacional) - HAUS-Hogar digital y contenidos Audiovisuales adaptados a los USuarios (IPT-2011-1049-430000) (Proy. Nacional) - IRENE - Incentivación del reciclaje de envases con NFC en España (PT-2012-1036-370000) (Proy. Nacional) - COMINN - Centro comercial interactivo con interacción natural (IPT- 2012-0883-430000) (Proy. Nacional) - REMEDISS - Red médica social sensorizada (IPT-2012-0882-430000) - OSAMI-Commons Open Source Infrastructure Ambient Inteligence Commons (TSI-020400-2009-92) (Proy. Internacional)Programa de Doctorado en Ingeniería Telemática por la Universidad Carlos III de MadridPresidente: Fernando Pescador del Oso.- Secretario: Andrés Marín López.- Vocal: Francisco José Bellido Outeiriñ

A framework for robust control of uncertainty in self-adaptive software connectors

Context and motivations. The desired behavior of a system in ubiquitous environments considers not only its correct functionality, but also the satisfaction of its non-functional properties, i.e., its quality of service. Given the heterogeneity and dynamism characterizing the ubiquitous environments and the need for continuous satisfaction of non-functional properties, self-adaptive solutions appear to be an appropriate approach to achieve interoperability. In this work, self-adaptation is adopted to enable software connectors to adapt the interaction protocols run by the connected components to let them communicate in a timely manner and with the required level of quality. However, this self-adaptation should be dependable, reliable and resilient to be adopted in dynamic, unpredictable environments with different sources of uncertainty. The majority of current approaches for the construction of self-adaptive software ignore the uncertainty underlying non-functional requirement verification and adaptation reasoning. Consequently, these approaches jeopardize system reliability and hinder the adoption of self-adaptive software in areas where dependability is of utmost importance. Objective. The main objective of this research is to properly handle the uncertainties in the non-functional requirement verification and the adaptation reasoning part of the self-adaptive feedback control loop of software connectors. This will enable a robust and runtime efficient adaptation in software connectors and make them reliable for usage in uncertain environments. Method. In the context of this thesis, a framework has been developed with the following functionalities: 1) Robust control of uncertainty in runtime requirement verification. The main activity in runtime verification is fine-tuning of the models that are adopted for runtime reasoning. The proposed stochastic approach is able to update the unknown parameters of the models at runtime even in the presence of incomplete and noisy observations. 2) Robust control of uncertainty in adaptation reasoning. A general methodology based on type-2 fuzzy logic has been introduced for the control of adaptation decision-making that adjusts the configuration of component connectors to the appropriate mode. The methodology enables a systematic development of fuzzy logic controllers that can derive the right mode for connectors even in the presence of measurement inaccuracy and adaptation policy conflicts. Results. The proposed model evolution mechanism is empirically evaluated, showing a significant precision of parameter estimation with an acceptable overhead at runtime. In addition, the fuzzy based controller, generated by the methodology, has been shown to be robust against uncertainties in the input data, efficient in terms of runtime overhead even in large-scale knowledge bases and stable in terms of control theory properties. We also demonstrate the applicability of the developed framework in a real-world domain. Thesis statement. We enable reliable and dependable self-adaptations of component connectors in unreliable environments with imperfect monitoring facilities and conflicting user opinions about adaptation policies by developing a framework which comprises: (a) mechanisms for robust model evolution, (b) a method for adaptation reasoning, and (c) tool support that allows an end-to-end application of the developed techniques in real-world domains