No description available.

Background. Environmental sustainability and reducing energy consumption are important and relevant topics today. Energy consumption by data centres is constantly increasing. One factor that could be affecting this is what web frameworks are being used. Objectives. We wanted to investigate whether there is a difference in energy consumption depending on the selected web framework for an API web server. An improvement should not come with overhanging negative side effects. Therefore, energy usage was to be contrasted with response time. In addition, we wanted to see how the choice of response format affects these metrics. In the case of finding any considerable impact on energy usage, without compromising the response time, the goal was to communicate this in order to increase the awareness among software developers. Methods. A literature review was done in order to gather existing information on how to conduct an experiment measuring software energy consumption. We evaluated available tools for measuring consumed application energy. An experiment then compared four popular web frameworks in regard to both energy usage, and response time. Django, Express, Laravel, and Spring Boot were selected for the experiment. Metrics measured were energy usage and response time. The experiment was executed with three different amounts of concurrent requests vusers = {10, 100, 250}. Results. The literature study resulted in a selection of software tools for measuring software energy consumption to choose from. The tool perf was chosen for the experiment. In the experiment, the response format was shown to affect the response time, but not the energy consumption. Increasing the amount of concurrent users made for larger differences between frameworks, both regarding energy usage and response time. Express and Spring Boot show the best performance in both regards for all amounts of concurrent requests. Conclusions. Express and Spring Boot are the clear winners out of the four compared frameworks. Both in terms of energy usage and response time, they had the best results. Django is not a web framework to recommend if response time is of importance.

The operation and control of the power system in an efficient way is important in order to keep the system secure, reliable and economical. With advancements in smart grid, several new algorithms have been developed for improved operation and control. These algorithms need to be extensively tested and validated in real time before applying to the real electric power grid. This work focuses on the development of a real time test bed for testing and validating power system control algorithms, hardware devices and cyber security vulnerability. The test bed developed utilizes several hardware components including relays, phasor measurement units, phasor data concentrator, programmable logic controllers and several software tools. Current work also integrates historian for power system monitoring and data archiving. Finally, two different power system test cases are simulated to demonstrate the applications of developed test bed. The developed test bed can also be used for power system education.

Large-scale distributed computing systems such as data centers are hosted on heterogeneous and networked servers that execute in a dynamic and uncertain operating environment, caused by factors such as time-varying user workload and various failures. Therefore, achieving stringent quality-of-service goals is a challenging task, requiring a comprehensive approach to performance control, fault diagnosis, and failure recovery. This work presents a model-based approach for fault management, which integrates limited lookahead control (LLC), diagnosis, and fault-tolerance concepts that: (1) enables systems to adapt to environment variations, (2) maintains the availability and reliability of the system, (3) facilitates system recovery from failures. We focused on memory leak errors in this thesis. A characterization function is designed to detect memory leaks. Then, a LLC is applied to enable the computing system to adapt efficiently to variations in the workload, and to enable the system recover from memory leaks and maintain functionality.

No description available.

Denna litteraturanalys går igenom åtgärderna för de problem som förekommer vid skapandet av online pvp-spel. Några av de vanliga problem som kan stötas på innefattar fördröjning, paketförlust, fusk, skalbarhet, synkronisering, uppdateringsfrekvens och säkerhet. Dessa problem kan sedan negativt påverka andra aspekter av spelet, inte minst game feel. För att förhindra detta bör specifika åtgärder implementeras. Inom just online pvp-spel kan grunden till nätverkshanteringen skapas med en klient/server-uppsättning som skickar små och snabba datapaket med hjälp av nätverksprotokollet UDP. Ytterligare lösningar som “dumma klienter”, “client-side prediction”, “server reconciliation”, “interpolation”, historik och tidsstämplar i datapaketen kan användas för att förbättra spelupplevelsen. I kombination med varandra skapar dessa åtgärder en stabil nätverksinfrastruktur för ett online pvp-spel. Då vissa av dessa tekniker kan kräva en del prestanda både på klienten och servern kan framtida arbeten kring dessa lösningar fokusera på optimering.

In recent years the technology of web application development has improved a lot and JavaScript frameworks such as React and Angular have increased in popularity. These frameworks use client-side rendering and have led to the rendering method’s increase in popularity compared to its previous conqueror; server-side rendering. Server-side rendering, however, is still a viable option in certain cases. For instance, it provides improved performance on computers depending on the hardware specification and search engine optimization. This thesis is an experimental study that aims to present knowledge regarding the rendering method's benefits and drawbacks. The study also presents when server-side rendering becomes beneficial to your web program compared to client-side rendering. The thesis also includes another rendering method using client-side rendering but with a configuration called virtualized. In this study, two identical web applications containing a grid were built. The rendering method using the server side was on one application and rendering methods using the client side were on the other application. The evaluation metrics of the rendering methods were the time to render the grid and how good of a user experience they provided. The results show that virtualized offers a faster rendering time and better user experience, especially at larger grids. Server-side rendering was faster than client-side rendering at all grid sizes and they had a similar user experience. Overall, this thesis suggests using virtualized when suited. Regarding server-side rendering, this thesis recommends using it carefully since it requires complex implementation and maintenance along with higher costs. Therefore, it comes down to the requirements of the application and if it is worth the complex implementation, cost, and maintenance.

Current Massively Multi-player Online Games (MMOGs) have enormous server-side bandwidth requirements. The costs of providing this bandwidth is in turn passed on to the consumer in the form of high monthly subscription fees. Prior work has primarily focused on distributing this bandwidth using peer-to-peer architectures, but these architectures have difficulty preventing cheating, overwhelming low resource peers, and maintaining consistent game state. We have developed a hybrid game architecture that combines client-server and peer-to-peer technologies to prevent cheating, maintain centralized and consistent game state, significantly reduce central server bandwidth, and prevent lower capacity players from being overwhelmed. By dramatically reducing the bandwidth needed to host a game without introducing additional liabilities, our hybrid architecture reduces the costs associated with that bandwidth and allows MMOG developers to reduce the cost of monthly subscription fees. In addition, because the central server will need less bandwidth per player, a single server is able to support considerably more concurrent players. Our experiments show that bandwidth can be reduced by up to 95% and a single server can support a game twice as large.

Existing database drivers use blocking socket I/O to exchange data with relational database management systems (RDBMS). To concurrently send multiple requests to a RDBMS with blocking database drivers, a separate thread must be used for each request. This approach has been used successfully for many years. However, we propose that using non-blocking socket I/O is faster and scales better under load. In this paper we introduce the Asynchronous Database Connectivity in Java (ADBCJ) framework. ADBCJ provides a common API for asynchronous RDBMS interaction. Various implementations of the ADBCJ API are used to show how utilizing non-blocking socket I/O is faster and scales better than using conventional database drivers and multiple threads for concurrency. Our experiments show a significant performance increase when using non- blocking socket I/O for asynchronous RDBMS access while using a minimal number of OS threads. Non-blocking socket I/O enables the ability to pipeline RDBMS requests which can improve performance significantly, especially over high latency networks. We also show the benefits of asynchronous database drivers on different web server architectures.

Mobile crowdsourcing solves complex problems by utilizing the untapped power of a crowd, connected through the fantastic mobile devices we use in our daily life. These gadgets are equipped with a versatile set of sensor that could be used for gathering data about a specific location in combination with questions to the human carrier. Common problems in crowdsourcing systems is how to ensure that the contributed data from the crowd is of a high quality and how to do task allocation fairly. A large population of users is often needed to ensure a high quality of data and coverage, every participant is important and the system have to do be designed with the population in mind.In this thesis we discuss the responsibilities of the server in a crowdsourcing system and presents a system model which tries to tackle the problems of quality and fairness. A prototype of the system model was developed (CrowdS) to determine its potential, for both Android and iOS devices.A long running test was performed to evaluate the performance of CrowdS with the main focus on determine how well the system performed in terms of coverage of the search area and fairness of earnings and prices. The test was executed on both platforms for a couple of weeks. The vast majority of all completed tasks were finished within 10 minutes of being created, with a median time of 3 minutes and 32 seconds seconds. Jain’s fairness index measured an overall high fairness for both the price of tasks at 0.944 and the earnings made by participants at 0.941. The radius of the search area had to be extended to maximum of 800 meters for roughly on third of the tasks to find the required number of participants. / Mobil crowdsourcing löser komplexa problem genom att utnyttja kapaciteten av en grupp, sammankopplad med de mobila enheter vi använder dagligen. Dessa maskiner är utrustade med en mångsidig uppsättning av sensorer som kan användas för att samla in data om en specifik plats i kombination med frågor till den mänskliga bäraren. Vanliga problem med gruppbaserad problemlösning är hur man försäkrar att den insamlade informationen är av en hög kvalite´ och hur man utför uppdragsallokering rättvist. En stor användargrupp behövs för att uppnå en hög kvalite´ av data och täckning, varenda deltagare är viktig och systemet måste utformas med denna användargrupp i åtanke.I denna avhandling diskuterar vi ansvaret som en server har i mobil gruppbaserad problemlösning och presenterar en systemmodel som försöker hantera problemen med kvalite´ och rättvisa. För att utvärdera systemmodellen utvecklades en prototyp (CrowdS), för både Android och iOS-enheter.Ett långvarande test utfördes för att utvärdera Crowds prestanda med huvudfokus på att bestämmahur bra systemet presterade inom täckning för sökområdet och rättvishet för vinster och priser. Testet utfördes på båda plattformarna under ett par veckor. Den stora majoriteten av alla utdelade uppgifter var avklarade inom 10 minuter efter att de hade skapas, med en median tid på 3 minuter och 32 sekunder. Jain’s rättvise index användes för att få en uppfattning om hur rättvist vinster och priser var för uppgifter, det räknades till 0,944 respektive 0,941. Radien för sökområdet behövde utsträckas till dess maximum av 800 meter för cirka en tredjedel av uppgifterna för att hitta det tillräckligt många deltagare.