Deterministic Object Management in Large Distributed Systems

Caching is a widely used technique to improve the scalability of distributed systems. A central issue with caching is maintaining object replicas consistent with their master copies. Large distributed systems, such as the Web, typically deploy heuristic-based consistency mechanisms, which increase delay and place extra load on the servers, while not providing guarantees that cached copies served to clients are up-to-date. Server-driven invalidation has been proposed as an approach to strong cache consistency, but it requires servers to keep track of which objects are cached by which clients. We propose an alternative approach to strong cache consistency, called MONARCH, which does not require servers to maintain per-client state. Our approach builds on a few key observations. Large and popular sites, which attract the majority of the traffic, construct their pages from distinct components with various characteristics. Components may have different content types, change characteristics, and semantics. These components are merged together to produce a monolithic page, and the information about their uniqueness is lost. In our view, pages should serve as containers holding distinct objects with heterogeneous type and change characteristics while preserving the boundaries between these objects. Servers compile object characteristics and information about relationships between containers and embedded objects into explicit object management commands. Servers piggyback these commands onto existing request/response traffic so that client caches can use these commands to make object management decisions. The use of explicit content control commands is a deterministic, rather than heuristic, object management mechanism that gives content providers more control over their content. The deterministic object management with strong cache consistency offered by MONARCH allows content providers to make more of their content cacheable. Furthermore, MONARCH enables content providers to expose internal structure of their pages to clients. We evaluated MONARCH using simulations with content collected from real Web sites. The results show that MONARCH provides strong cache consistency for all objects, even for unpredictably changing ones, and incurs smaller byte and message overhead than heuristic policies. The results also show that as the request arrival rate or the number of clients increases, the amount of server state maintained by MONARCH remains the same while the amount of server state incurred by server invalidation mechanisms grows

Adaptive Caching of Distributed Components

Die Zugriffslokalität referenzierter Daten ist eine wichtige Eigenschaft verteilter Anwendungen. Lokales Zwischenspeichern abgefragter entfernter Daten (Caching) wird vielfach bei der Entwicklung solcher Anwendungen eingesetzt, um diese Eigenschaft auszunutzen. Anschliessende Zugriffe auf diese Daten können so beschleunigt werden, indem sie aus dem lokalen Zwischenspeicher bedient werden. Gegenwärtige Middleware-Architekturen bieten dem Anwendungsprogrammierer jedoch kaum Unterstützung für diesen nicht-funktionalen Aspekt. Die vorliegende Arbeit versucht deshalb, Caching als separaten, konfigurierbaren Middleware-Dienst auszulagern. Durch die Einbindung in den Softwareentwicklungsprozess wird die frühzeitige Modellierung und spätere Wiederverwendung caching-spezifischer Metadaten gewährleistet. Zur Laufzeit kann sich das entwickelte System außerdem bezüglich der Cachebarkeit von Daten adaptiv an geändertes Nutzungsverhalten anpassen.Locality of reference is an important property of distributed applications. Caching is typically employed during the development of such applications to exploit this property by locally storing queried data: Subsequent accesses can be accelerated by serving their results immediately form the local store. Current middleware architectures however hardly support this non-functional aspect. The thesis at hand thus tries outsource caching as a separate, configurable middleware service. Integration into the software development lifecycle provides for early capturing, modeling, and later reuse of cachingrelated metadata. At runtime, the implemented system can adapt to caching access characteristics with respect to data cacheability properties, thus healing misconfigurations and optimizing itself to an appropriate configuration. Speculative prefetching of data probably queried in the immediate future complements the presented approach

Web-Based Management and Lending System

Cílem této práce je analýza a implementace webového systému pro správu a půjčování zařízení, které uživatelům zprostředkuje přehled dat v systému a historii transakcí zařízení. Výsledná aplikace byla implementována v PHP s využitím Nette Frameworku, MySQL a AJAXu. V první polovině této práce je probrána analýza existujících platforem, popis jednotlivých fází implementace a seznam využitých návrhových vzorů. Druhá polovina pojednává o testování, využitých komponentách a jejich opodstatnění, a nakonec sumarizuje využitelnost implementovaného systému. Výsledkem této práce je implementace systému pro správu a půjčování zařízení, který uživatelům umožňuje vést efektivní evidenci půjčování položek.The aim of this thesis is to analyze and implement a web-based equipment checkout system, which provides an organized outlook on system data and equipment transactions history. The final application was implemented as a server-side application using Nette Framework under PHP, MySQL and AJAX. The first half of this thesis investigates existing solutions, describes the implementation phases and looks at design patterns present in the code. The second half of the paper examines the testing, mentions all used add-on components and their purpose, and finally assesses the usability of the implemented system. The result of this paper is an implemented equipment checkout system giving its users an effective way to manage item lending.

IT infrastructure & microservices authentication

Mestrado IPB-ESTGBIOma - Integrated solutions in BIOeconomy for the Mobilization of the Agrifood chain project is structured in 6 PPS (Products, Processes, and Services) out of which, a part of PPS2 is covered in this work. This work resulted in the second deliverable of PPS2 which is defined as PPS2.A1.E2 - IT infrastructure design and graphical interface conceptual design. BIOma project is in the early stage and this deliverable is a design task of the project. For defining the system architecture, requirements, UML diagrams, physical architecture, and logical architecture have been proposed. The system architecture is based on microservices due to its advantages like scalability and maintainability for bigger projects like BIOma where several sensors are used for big data analysis. Special attention has been devoted to the research and study for the authentication and authorization of users and devices in a microservices architecture. The proposed authentication solution is a result of research made for microservices authentication where it was concluded that using a separate microservice for user authentication is the best solution. FIWARE is an open-source initiative defining a universal set of standards for context data management that facilitates the development of Smart solutions for different domains like Smart Cities, Smart Industry, Smart Agrifood, and Smart Energy. FIWARE’s PEP (Policy Enforcement Point) proxy solution has been proposed in this work for the better management of user’s identities, and client-side certificates have been proposed for authentication of IoT (Internet of Things) devices. The communication between microservices is done through AMQP (Advanced Message Queuing Protocol), and between IoT devices and microservices is done through MQTT (Message Queuing Telemetry Transport) protocol

Interaction and Behaviour Evaluation for Smart Homes: Data Collection and Analytics in the ScaledHome Project

Nowadays more and more devices are becoming "smart", in fact they can take autonomous decision and interact proactively with the surrounding environment. Smart home is just one of the most popular terms related with this relevant change we are witnessing and its relevance in this project is mainly due to the fact that the residential sector account an important percentage in terms of energy consumption. New ways to share and save energy have to be taken into account in order to optimize the usage of the devices needed by houses to make the environment cozy and comfortable for their inhabitants. The work done with Professor Turgut's team has improved the knowledge in the smart home system area providing a scalable and reliable architecture, a new dataset and an example of application of these data useful to save energy while satisfying the demands of its inhabitants

Mobility-aware Software-Defined Service-Centric Networking for Service Provisioning in Urban Environments

Disruptive applications for mobile devices, such as the Internet of Things, Connected and Autonomous Vehicles, Immersive Media, and others, have requirements that the current Cloud Computing paradigm cannot meet. These unmet requirements bring the necessity to deploy geographically distributed computing architectures, such as Fog and Mobile Edge Computing. However, bringing computing close to users has its costs. One example of cost is the complexity introduced by the management of the mobility of the devices at the edge. This mobility may lead to issues, such as interruption of the communication with service instances hosted at the edge or an increase in communication latency during mobility events, e.g., handover. These issues, caused by the lack of mobility-aware service management solutions, result in degradation in service provisioning. The present thesis proposes a series of protocols and algorithms to handle user and service mobility at the edge of the network. User mobility is characterized when user change access points of wireless networks, while service mobility happens when services have to be provisioned from different hosts. It assembles them in a solution for mobility-aware service orchestration based on Information-Centric Networking (ICN) and runs on top of Software-Defined Networking (SDN). This solution addresses three issues related to handling user mobility at the edge: (i) proactive support for user mobility events, (ii) service instance addressing management, and (iii) distributed application state data management. For (i), we propose a proactive SDN-based handover scheme. For (ii), we propose an ICN addressing strategy to remove the necessity of updating addresses after service mobility events. For (iii), we propose a graph-based framework for state data placement in the network nodes that accounts for user mobility and latency requirements. The protocols and algorithms proposed in this thesis were compared with different approaches from the literature through simulation. Our results show that the proposed solution can reduce service interruption and latency in the presence of user and service mobility events while maintaining reasonable overhead costs regarding control messages sent in the network by the SDN controller

Scalable hosting of web applications

Modern Web sites have evolved from simple monolithic systems to complex multitiered systems. In contrast to traditional Web sites, these sites do not simply deliver pre-written content but dynamically generate content using (one or more) multi-tiered Web applications. In this thesis, we addressed the question: How to host multi-tiered Web applications in a scalable manner? Scaling up a Web application requires scaling its individual tiers. To this end, various research works have proposed techniques that employ replication or caching solutions at different tiers. However, most of these techniques aim to optimize the performance of individual tiers and not the entire application. A key observation made in our research is that there exists no elixir technique that performs the best for allWeb applications. Effective hosting of a Web application requires careful selection and deployment of several techniques at different tiers. To this end, we present several caching and replication strategies, such as GlobeCBC, GlobeDB and GlobeTP, to improve the scalability of different tiers of a Web application. While these techniques and systems improve the performance of the individual tiers (and eventually the application), an application's administrator is not only interested in the performance of its individual tiers but also in its endto- end performance. To this end, we propose a resource provisioning approach that allows us to choose the best resource configuration for hosting a Web application such that its end-to-end response time can be optimized with minimum usage of resources. The proposed approach is based on an analytical model for multi-tier systems, which allows us to derive expressions for estimating the mean end-to-end response time and its variance.Steen, M.R. van [Promotor]Pierre, G.E.O. [Copromotor

Digitization of industrial quality control procedures applied to visual and geometrical inspections

Mestrado de dupla diplomação com a UTFPR - Universidade Tecnológica Federal do ParanáIndustries quality control procedures are usually dependent on gauge inspection tools, and these tools are used to inspect visual and geometrical tolerance conformity. Operators are guided during an inspection by using paper tutorials that assist them in performing their tasks and registering the result of the performed analysis. This traditional method of registering information may be misleading, lowering the effectiveness of the quality control by providing inaccurate and error-prone inspection results. This work implements a system that uses emergent technologies (e.g., Human-Machine Interfaces, Virtual Reality, Distributed Systems, Cloud Computing, and Internet of Things (IoT)) to propose a costeffective solution that supports operators and quality control managers in the realization and data collection of gauge inspection control procedures. The final system was deployed in an industrial production plant, with the delivered results showing its efficiency, robustness, and highly positive feedback from the operators and managers. The software may offer a quicker and efficient execution of analysis tasks, significantly decreasing the setup time required to change the inspected product reference