An approximation-based load-balancing algorithm with admission control for cluster web servers with dynamic workloads

Abstract

The growth of web-based applications in business and e-commerce is building up demands for high performance web servers for better throughputs and lower user-perceived latency. These demands are leading to a widespread substitution of powerful single servers by robust newcomers, cluster web servers, in many enterprise companies. In this respect the load-balancing algorithms play an important role in boosting the performance of cluster servers. The previous load-balancing algorithms which were designed for the handling of static contents in web services suffer from significant performance degradation under dynamic and database-driven workloads. Regarding this, we propose an approximation-based load-balancing algorithm with admission control for cluster-based web servers in this study. Since it is difficult to accurately determine the loads of web servers through feedbacks from distributed agents in web servers, we propose an analytical model of a web server to estimate the web servers' loads. To achieve this, the algorithm classifies requests based on their service times and track numbers of outstanding requests for each class of each web server node and also based on their resource demands to dynamically estimate the loads of each node. For the error handling of the model a proportional integral (PI) controller from control theory is used. Then the estimated available capacity of each web server is used for load balancing and admission control decisions. The implementation results with a standard benchmark confirm the effectiveness of the proposed scheme, which improves both the mean response time and the throughput An approximation-based load-balancing algorithm 441 of the cluster compared to rival load-balancing algorithms, and also avoids situations in which the cluster is overloaded, even when the request rates are beyond the cluster capacity.Keywords Cluster-based web server · Dynamic load-balancing algorithm · Admission control · Analytical model of web server · Feedback controller design

Using Long-Term Prediction for Web Service Network Traffic Loads

“…Optimizing resource management has been studied using short-term prediction [1][2][3][4]. The samples taken for those studies were between one and five seconds and were used to provide a single step prediction.…”

“…The samples taken for those studies were between one and five seconds and were used to provide a single step prediction. This provided a mechanism for scheduling jobs in distributed systems [1,4], web service order [3], and network load balancing [2]. In each case the prediction ranged from several seconds in the future to fifteen minutes.…”

“…In each case the prediction ranged from several seconds in the future to fifteen minutes. It was also determined that the more steps used, the less accurate the prediction becomes [3,5].…”

Estudo de algoritmos de controle de admissão em servidores Web distribuídos com QoS

“…Diversos métodos como controle de admissão ou políticas de escalonamento especializadas (Sharifian et al, 2010) ou a combinação de ambos foram propostos.…”

“…Esta ferramenta representa cargas de trabalho em rajadas, com distribuição exponencial, entre outras. Ela é utilizada em vários trabalhos científicos que pesquisam Web cluster, como em (Sharifian et al, 2008), (Sharifian et al, 2010), (Shan et al, 2002), (Shan et al, 2005).…”