An Experimental Study on Virtual Machine Live Migration Impact on Services Performance

One important benefit of servers' virtualization is the reduction of the maintenance complexity of infrastructures. A key feature is servers' live migration which allows virtual servers to be exchanged between physical machines without stopping their services. However, virtualization also has some drawbacks caused by the overhead generated. Our research evaluated live migration process overhead, on real and virtual environments, noticed from the client's side regarding two different services: web and database. YCSB and ab Benchmark were adopted as workloads. Almost all tests on real environment overcame those on virtual, with both benchmarks. The impact of the live migration in the services was evident, proving to be more effective on real machines than on virtual machines. We found the DB service accommodated better to the virtual environment and to migration than Web service. We also considered an environment with multiple migrations which presented a higher degradation than when only one migration is performed

Understanding the Impact of Cloud Computing Patterns on Performance and Energy Consumption

RÉSUMÉ Les patrons infonuagiques sont des solutions abstraites à des problèmes récurrents de conception dans le domaine de l'infonuagique. Bien que des travaux antérieurs aient prouvé que ces patrons peuvent améliorer la qualité de service des applications infonuagiques, leur impact sur la consommation d'énergie reste encore inconnu. Pourtant l'efficacité énergétique est un défi majeur pour les systèmes infonuagiques. Actuellement, 10\% de l'électricité mondiale est consommée par les serveurs, les ordinateurs portables, les tablettes et les téléphones intelligents. La consommation d'énergie d'un système dépend non seulement de son infrastructure matérielle, mais aussi de ses différentes couches logicielles. Le matériel, le firmware, le système d'exploitation, et les différentes composantes logicielles d'une application infonuagique, contribuent tous à déterminer son empreinte énergétique. De ce fait, pour une meilleure efficacité énergétique, il est important d’améliorer l’efficacité énergétique de toutes les couches matérielles et logicielles du système infonuagique, ce qui inclut les applications déployées dans le système infonuagique. Dans ce mémoire, nous examinons l'impact de six patrons infonuagiques (Local Database proxy, Local Sharding Based Router, Priority Queue, Competing Consumers, Gatekeeper and Pipes and Filters) sur la consommation d'énergie de deux applications multi-traitement et multi-processus déployées dans un système infonuagique. La consommation d'énergie est mesurée avec l’outil Power-API, une interface de programmation d'application (API) écrite en Java et permettant de mesurer la consommation d'énergie au niveau du processus. Les résultats de nos analyses montrent que les patrons étudiés peuvent réduire efficacement la consommation d'énergie d'une application infonuagique, mais pas dans tous les contextes. D'une manière générale, nous prouvons qu'il y a un compromis à faire entre performance et efficacité énergétique, lors du développement d'une application infonuagique. De plus, nos résultats montrent que la migration d'une application vers une architecture de micro-services peut améliorer les performances de l'application, tout en réduisant considérablement sa consommation d'énergie. Nous résumons nos contributions sous forme de recommandations que les développeurs et les architectes logiciels peuvent suivre lors de la conception et la mise en œuvre de leurs applications.----------ABSTRACT Cloud Patterns are abstract solutions to recurrent design problems in the cloud. Previous work has shown that these patterns can improve the Quality of Service (QoS) of cloud applications but their impact on energy consumption is still unknown. Yet, energy consumption is the biggest challenge that cloud computing systems (the backbone of high-tech economy) face today. In fact, 10% of the world’s electricity is now being consumed by servers, laptops, tablets and smart phones. Energy consumption has complex dependencies on the hard- ware platform, and the multiple software layers. The hardware, its firmware, the operating system, and the various software components used by a cloud application, all contribute to determining the energy footprint. Hence, increasing a data center efficiency will eventually improve energy efficiency. Similarly, software itself can affect the internal design of cloud-based applications to optimize hardware utilization to lower energy consumption. In this work, we conduct an empirical study on two multi-processing and multi-threaded cloud- based applications deployed in the cloud, to investigate the individual and the combined impact of six cloud patterns (Local Database proxy, Local Sharding Based Router, Priority Queue, Competing Consumers, Gatekeeper and Pipes and Filters) on the energy consumption. We measure the energy consumption using Power-API; an application programming interface (API) written in Java to monitor the energy consumed at the process-level. Results show that cloud patterns can effectively reduce the energy consumption of a cloud application, but not in all cases. In general, there appear to be a trade-off between an improved response time of the application and the energy consumption. Moreover, our findings show that migrating an application to microservices architecture can improve the performance of the application, while significantly reducing its energy consumption. We summarize our contributions in the form of guidelines that developers and software architects can follow during the implementation of the cloud-based applications

Data modeling with NoSQL : how, when and why

Tese de mestrado integrado. Engenharia Informática e Computação. Faculdade de Engenharia. Universidade do Porto. 201

VISOR: virtual machine images management service for cloud infarestructures

Cloud Computing is a relatively novel paradigm that aims to fulfill the computing as utility dream. It has appeared to bring the possibility of providing computing resources (such as servers, storage and networks) as a service and on demand, making them accessible through common Internet protocols. Through cloud offers, users only need to pay for the amount of resources they need and for the time they use them. Virtualization is the clouds key technology, acting upon virtual machine images to deliver fully functional virtual machine instances. Therefore, virtual machine images play an important role in Cloud Computing and their efficient management becomes a key concern that should be carefully addressed. To tackle this requirement, most cloud offers provide their own image repository, where images are stored and retrieved from, in order to instantiate new virtual machines. However, the rise of Cloud Computing has brought new problems in managing large collections of images. Existing image repositories are not able to efficiently manage, store and catalogue virtual machine images from other clouds through the same centralized service repository. This becomes especially important when considering the management of multiple heterogeneous cloud offers. In fact, despite the hype around Cloud Computing, there are still existing barriers to its widespread adoption. Among them, clouds interoperability is one of the most notable issues. Interoperability limitations arise from the fact that current cloud offers provide proprietary interfaces, and their services are tied to their own requirements. Therefore, when dealing with multiple heterogeneous clouds, users face hard to manage integration and compatibility issues. The management and delivery of virtual machine images across different clouds is an example of such interoperability constraints. This dissertation presents VISOR, a cloud agnostic virtual machine images management service and repository. Our work towards VISOR aims to provide a service not designed to fit in a specific cloud offer but rather to overreach sharing and interoperability limitations among different clouds. With VISOR, the management of clouds interoperability can be seamlessly abstracted from the underlying procedures details. In this way, it aims to provide users with the ability to manage and expose virtual machine images across heterogeneous clouds, throughout the same generic and centralized repository and management service. VISOR is an open source software with a community-driven development process, thus it can be freely customized and further improved by everyone. The conducted tests to evaluate its performance and resources usage rate have shown VISOR as a stable and high performance service, even when compared with other services already in production. Lastly, placing clouds as the main target audience is not a limitation for other use cases. In fact, virtualization and virtual machine images are not exclusively linked to cloud environments. Therefore and given the service agnostic design concerns, it is possible to adapt it to other usage scenarios as well.A Computação em Nuvem (”Cloud Computing”) é um paradigma relativamente novo que visa cumprir o sonho de fornecer a computação como um serviço. O mesmo surgiu para possibilitar o fornecimento de recursos de computação (servidores, armazenamento e redes) como um serviço de acordo com as necessidades dos utilizadores, tornando-os acessíveis através de protocolos de Internet comuns. Através das ofertas de ”cloud”, os utilizadores apenas pagam pela quantidade de recursos que precisam e pelo tempo que os usam. A virtualização é a tecnologia chave das ”clouds”, atuando sobre imagens de máquinas virtuais de forma a gerar máquinas virtuais totalmente funcionais. Sendo assim, as imagens de máquinas virtuais desempenham um papel fundamental no ”Cloud Computing” e a sua gestão eficiente torna-se um requisito que deve ser cuidadosamente analisado. Para fazer face a tal necessidade, a maioria das ofertas de ”cloud” fornece o seu próprio repositório de imagens, onde as mesmas são armazenadas e de onde são copiadas a fim de criar novas máquinas virtuais. Contudo, com o crescimento do ”Cloud Computing” surgiram novos problemas na gestão de grandes conjuntos de imagens. Os repositórios existentes não são capazes de gerir, armazenar e catalogar images de máquinas virtuais de forma eficiente a partir de outras ”clouds”, mantendo um único repositório e serviço centralizado. Esta necessidade torna-se especialmente importante quando se considera a gestão de múltiplas ”clouds” heterogéneas. Na verdade, apesar da promoção extrema do ”Cloud Computing”, ainda existem barreiras à sua adoção generalizada. Entre elas, a interoperabilidade entre ”clouds” é um dos constrangimentos mais notáveis. As limitações de interoperabilidade surgem do fato de as ofertas de ”cloud” atuais possuírem interfaces proprietárias, e de os seus serviços estarem vinculados às suas próprias necessidades. Os utilizadores enfrentam assim problemas de compatibilidade e integração difíceis de gerir, ao lidar com ”clouds” de diferentes fornecedores. A gestão e disponibilização de imagens de máquinas virtuais entre diferentes ”clouds” é um exemplo de tais restrições de interoperabilidade. Esta dissertação apresenta o VISOR, o qual é um repositório e serviço de gestão de imagens de máquinas virtuais genérico. O nosso trabalho em torno do VISOR visa proporcionar um serviço que não foi concebido para lidar com uma ”cloud” específica, mas sim para superar as limitações de interoperabilidade entre ”clouds”. Com o VISOR, a gestão da interoperabilidade entre ”clouds” é abstraída dos detalhes subjacentes. Desta forma pretende-se proporcionar aos utilizadores a capacidade de gerir e expor imagens entre ”clouds” heterogéneas, mantendo um repositório e serviço de gestão centralizados. O VISOR é um software de código livre com um processo de desenvolvimento aberto. O mesmo pode ser livremente personalizado e melhorado por qualquer pessoa. Os testes realizados para avaliar o seu desempenho e a taxa de utilização de recursos mostraram o VISOR como sendo um serviço estável e de alto desempenho, mesmo quando comparado com outros serviços já em utilização. Por fim, colocar as ”clouds” como principal público-alvo não representa uma limitação para outros tipos de utilização. Na verdade, as imagens de máquinas virtuais e a virtualização não estão exclusivamente ligadas a ambientes de ”cloud”. Assim sendo, e tendo em conta as preocupações tidas no desenho de um serviço genérico, também é possível adaptar o nosso serviço a outros cenários de utilização

A Systematic Mapping Study of MMOG Backend Architectures

The advent of utility computing has revolutionized almost every sector of traditional software development. Especially commercial cloud computing services, pioneered by the likes of Amazon, Google and Microsoft, have provided an unprecedented opportunity for the fast and sustainable development of complex distributed systems. Nevertheless, existing models and tools aim primarily for systems where resource usage—by humans and bots alike—is logically and physically quite disperse resulting in a low likelihood of conflicting resource access. However, a number of resource-intensive applications, such as Massively Multiplayer Online Games (MMOGs) and large-scale simulations introduce a requirement for a very large common state with many actors accessing it simultaneously and thus a high likelihood of conflicting resource access. This paper presents a systematic mapping study of the state-of-the-art in software technology aiming explicitly to support the development of MMOGs, a class of large-scale, resource-intensive software systems.By examining the main focus of a diverse set of related publications, we identify a list of criteria that are important for MMOG development. Then, we categorize the selected studies based on the inferred criteria in order to compare their approach, unveil the challenges faced in each of them and reveal research trends that might be present. Finally we attempt to identify research directions which appear promising for enabling the use of standardized technology for this class of systems

A Systematic Mapping Study of MMOG Backend Architectures

The advent of utility computing has revolutionized almost every sector of traditional software development. Especially commercial cloud computing services, pioneered by the likes of Amazon, Google and Microsoft, have provided an unprecedented opportunity for the fast and sustainable development of complex distributed systems. Nevertheless, existing models and tools aim primarily for systems where resource usage—by humans and bots alike—is logically and physically quite disperse resulting in a low likelihood of conflicting resource access. However, a number of resource-intensive applications, such as Massively Multiplayer Online Games (MMOGs) and large-scale simulations introduce a requirement for a very large common state with many actors accessing it simultaneously and thus a high likelihood of conflicting resource access. This paper presents a systematic mapping study of the state-of-the-art in software technology aiming explicitly to support the development of MMOGs, a class of large-scale, resource-intensive software systems.By examining the main focus of a diverse set of related publications, we identify a list of criteria that are important for MMOG development. Then, we categorize the selected studies based on the inferred criteria in order to compare their approach, unveil the challenges faced in each of them and reveal research trends that might be present. Finally we attempt to identify research directions which appear promising for enabling the use of standardized technology for this class of systems

Multi-Perspective Evaluation of Relational and Graph Databases

How to store data is an enduring topic in the computer science field, and traditional relational databases have done this well and are still widely used today. However, with the growth of non-relational data and the challenges in the big data era, a series of NoSQL databases have come into view. Thus, comparing, evaluating, and choosing a better database has become a worthy topic of research. In this thesis, an experiment that can store the same data set and execute the same tasks or workload on the relational, graph and multi-model databases is designed. The investigation proposes how to adapt relational data, tables on a graph database and, conversely, store graph data on a relational database. Similarly, the tasks performed are unified across query languages. We conducted exhaustive experiments to compare and report the performance of the three databases. In addition, we propose a workload classification method to analyze the performance of the databases and compare multiple aspects of the database from an end-user perspective. We have selected PostgreSQL, ArangoDB, Neo4j as representatives. The comparison in terms of task execution time does not have any database that completely wins. The results show that relational databases have performance advantages for tasks such as data import, but the execution of multi-table join tasks is slow and graph algorithm support is lacking. The multi-model databases have impressive support for simultaneous storage of multiple data formats and unified language queries, but the performance is not outstanding. The graph database has strong graph algorithm support and intuitive support for graph query language, but it is also important to consider whether the format and interrelationships of the original data, etc. can be well converted into graph format

Modelling and managing service-level agreements in the context of 5G neutral hosting platforms

This project has received funding from the European Union’s Horizon 2020 research andinnovation programme under grant agreement No 761508 (5GCity project) and theSpanish national project 5GCity (TEC2016-76795-C6-1-R)This document contains the study and development of Service-Level Agreement (SLA) management mechanisms in the context of a 5G neutral host platform. The infrastructure involved in a neutral host platform is evaluated by an SLA Manager that handles the database of agreements for all the users, and verifies if the monitored data complies with the thresholds stated in the Service-Level Objectives (SLO) agreed in the SLAs. Neutral host is a platform that has different levels of virtualization over a 5G infrastructure. It starts from a sliced network infrastructure for logic separation between tenants, which in the next level of virtualization, can host 5G services with Network Functions Virtualization (NFV) techniques. This virtual platform runs on top of a physical infrastructure that not only covers data centres like in cloud platforms, but also includes access networks, edge computing and distributed cloud elements. Evaluating through all this infrastructure adds new levels of complexity for monitoring and obtaining an accurate value for any Key Performance Indicator, or high-level parameters for Quality of Service. This challenge is faced with a software module, called SLA Manager, which identifies the different involved infrastructure elements and creates monitoring jobs according to highlevel requirements described in each SLO to obtain low-level infrastructure data. This data is then computed to obtain a high-level value to compare latter with an SLO threshold and verify if there is a violation. Availability is the main KPI on which this study focuses. A generic SLA template body is presented for being stored in a NoSQL database solution, able to adapt to any new service deployed over new technologies that may be deployed by the neutral host, and to add flexibility and scalability to the solution. Results show that the accuracy and reliability of the high-level objectives stated in the SLOs obey the standards required for 5G applications. The system quickly detects any outage and gives feedback to the platform to recover and avoid any violation. Delay times for detection are observed in order to provide exact measurements for availability levels. The report ends with conclusions and future development lines, as well as ethical and sustainability considerations the study involves