Adaptação de protocolos distribuídos simétricos pelo texto à dinamicidade e heterogeneidade da carga do ambiente de execução através de oráculos de latência.

Abstract

Distributed protocoLs with textual simmetry can be configured by the roles played by diíferent participauts during the executiou of the protocols. Moreover, such a configuration raay impact the performance of the protocol in a positive or negative way, depending on the configuration chosen. Ou the other hand, it is not, possible to ensure an efficient configuration a priori when considering an execution environment with heterogeneous and dynamic workload. Consequently, distributed protocols with textual simmetry may suffer performance degradation on these. environments. In this thesis we investigated the use of adaptation by means of latency oracles to improve the performance of distributed protocols with textual simmetry that execute in environments subject to heterogeneous and dynamic workload. Such an investigation was conducted through both analytical and experimental studies on the performance of consensus protocols equiped with an adaptive solution to the process ordering problem. During the analytical study it was constructed a performance model for the consensus protocol using the formal definition of latency oracles. introduced in this work. From this performance model it was possible to demonstrate the efficiency of the adaptive solution and, consequently, the performance gaias to the protocol that used it. Following the same objective, but considering a different method, the experimental study consisted of simulations and measurements in a real environment. In this case, we designed and implemented an adaptive consensus system encapsulated in an application for intrusion tolerance in the Internet. The performance of the adaptive consensus system was analyzed by means of comparison using its non-adaptive counterpart. The adaptive system outperformed the non-adaptive one in both simulations and measurements with performance gains of as much as 76,1% and 45.4%, respectively. Note that. in the analytical and experimental studies, adaptation was used to solve the process ordering problem that characterizes a number of distributed protocols with textual simmetry. Therefore, this thesis gives theoretical and practical contributions in the context of adaptive distributed protocols with textual simmetry that execute on environments subject to heterogeneous and dynamic workload. It is important to emphasize that the strategy of using latency oracles to construct adaptive solutions respects one of the most important principies of software engineermg, whieh is the separation of concerns. Futhermore, it favors the analytical study on the performance of such adaptive solutions.