Master of Engineering (Research) / This thesis presents a new approach to ensuring fair service for highly concurrent requests. Our design uses the advantages of staged event-driven architecture (SEDA) to support high-concurrent loadings and makes use of control theory to manage the system performance. In order to guarantee the quality of service is fairly made to each request, based on SEDA, the control system for fairness is developed as a combination of a global control framework and a set of local self-tune stags. The global control framework is used to control the performance of the whole staged network at the top-level, aimed at coordinating the performance of the stages in the network. On the other hand, each self-tune stage under the control framework is built on the thread pool model, and will use automatic control theory to adjust its performance locally in order to meet the overall target performance. The automatic control system in each stage consists of an automatic modeling mechanism and a feedback module, which optimizes the controller parameters in the system automatically and guarantees the quality of performance (service rate here) for the stage at runtime. Based on mathematical proof and simulation results, our designs are implemented in a SEDA-based web server running in a dynamic loading environment. Results demonstrate that the performance of the new system in the real world is almost the same as the theoretical results. It demonstrates that the design is able to adaptively ensure the quality of service to the high-concurrent requests fairly. Compared to the original SEDA design, our design is an effective and handy approach to significantly enhancing the performance of SEDA in a variety of aspects, including fairer service, faster convergent speed, better robustness, higher accuracy and ease of deployment in various practical applications.

Consider a multi-priority, nonpreemptive, N-server Poisson arrival queueing system. The number of servers requested by an arrival has a known probability distribution. Service times are negative exponential. In order to save available servers for higher priority customers, arriving customers of each lower priority are deliberately queued whenever the number of servers busy equals or exceeds a given priority-dependent cutoff number. A queued priority i customer enters service the instant the number of servers busy is at most the respective cutoff number of servers minus the number of servers requested (by the customer) and all higher priority queues are empty. In other words the queueing discipline is in a sense HOL by priorities, FCFS within a priority. All servers requested by a customer start service simultaneously; service completion instants are independent. We derive the priority i waiting time distribution (in transform domain) and other system statistics.

Awareness servers provide information about a person to help observers determine whether a person is available for contact. A trade -off exists in these systems: more sources of information, and higher fidelity in those sources, can improve peoples decisions, but each increase in information reduces privacy. In this thesis, we look at whether the type of relationship between the observer and the person being observed can be used to manage this trade-off. We conducted a survey that asked people what amount of information from different sources that they would disclose to seven different relationship types. We found that in more than half of the cases, people would give different amounts of information to different relationships. We then constructed a prototype system and conducted a Wizard of Oz experiment where we took the system into the real world and observed individuals using it. Our results suggest that awareness servers can be improved by allowing finer-grained control than what is currently available.

Optimizing database systems to achieve the maximum attainable throughput of the underlying hardware is one of the many difficult tasks that face Database Administrators. With the increased use of database systems in many environments, this task has even become more difficult. One of the parameters that needs to be configured is the number of worker tasks that the database server uses (the multiprogramming level). This thesis will focus on how to automatically adjust the number of database server worker tasks to achieve maximum throughput under varying workload characteristics. The underlying intuition is that every workload has an optimal multiprogramming level that can achieve the best throughput given the workload characteristic.

Optimizing database systems to achieve the maximum attainable throughput of the underlying hardware is one of the many difficult tasks that face Database Administrators. With the increased use of database systems in many environments, this task has even become more difficult. One of the parameters that needs to be configured is the number of worker tasks that the database server uses (the multiprogramming level). This thesis will focus on how to automatically adjust the number of database server worker tasks to achieve maximum throughput under varying workload characteristics. The underlying intuition is that every workload has an optimal multiprogramming level that can achieve the best throughput given the workload characteristic.

Awareness servers provide information about a person to help observers determine whether a person is available for contact. A trade -off exists in these systems: more sources of information, and higher fidelity in those sources, can improve peoples decisions, but each increase in information reduces privacy. In this thesis, we look at whether the type of relationship between the observer and the person being observed can be used to manage this trade-off. We conducted a survey that asked people what amount of information from different sources that they would disclose to seven different relationship types. We found that in more than half of the cases, people would give different amounts of information to different relationships. We then constructed a prototype system and conducted a Wizard of Oz experiment where we took the system into the real world and observed individuals using it. Our results suggest that awareness servers can be improved by allowing finer-grained control than what is currently available.

Thesis (M.S.)--Worcester Polytechnic Institute. / Keywords: multimedia; content adaptation; scalable web server. Includes bibliographical references (p. 68-74).

Thesis (M.S. in Computer Science)--Naval Postgraduate School, September 2003. / Thesis advisor(s): Neil C. Rowe, Gary L. Kreeger. Includes bibliographical references (p. 121-122). Also available online.

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Master of Engineering (Research) / This thesis presents a new approach to ensuring fair service for highly concurrent requests. Our design uses the advantages of staged event-driven architecture (SEDA) to support high-concurrent loadings and makes use of control theory to manage the system performance. In order to guarantee the quality of service is fairly made to each request, based on SEDA, the control system for fairness is developed as a combination of a global control framework and a set of local self-tune stags. The global control framework is used to control the performance of the whole staged network at the top-level, aimed at coordinating the performance of the stages in the network. On the other hand, each self-tune stage under the control framework is built on the thread pool model, and will use automatic control theory to adjust its performance locally in order to meet the overall target performance. The automatic control system in each stage consists of an automatic modeling mechanism and a feedback module, which optimizes the controller parameters in the system automatically and guarantees the quality of performance (service rate here) for the stage at runtime. Based on mathematical proof and simulation results, our designs are implemented in a SEDA-based web server running in a dynamic loading environment. Results demonstrate that the performance of the new system in the real world is almost the same as the theoretical results. It demonstrates that the design is able to adaptively ensure the quality of service to the high-concurrent requests fairly. Compared to the original SEDA design, our design is an effective and handy approach to significantly enhancing the performance of SEDA in a variety of aspects, including fairer service, faster convergent speed, better robustness, higher accuracy and ease of deployment in various practical applications.