A Cluster-Based Web System Providing Differentiated and Guaranteed Services

Abstract

Abstract. In a world where many users rely on the Web for up-to-date personal and business information and transactions, it is fundamental to build Web systems that allow service providers to differentiate user expectations with multi-class Service Level Agreements (SLAs). In this paper we focus on the server components of the Web, by implementing QoS principles in a Web-server cluster that is, an architecture composed by multiple servers and one front-end node called Web switch. We first propose a methodology to determine a set of confident SLAs in a real Web cluster for multiple classes of users and services. We then decide to implement at the Web switch level all mechanisms that transform a best-effort Web cluster into a QoS-enhanced system. We also compare three QoS-aware policies through experimental results in a real test-bed system. We show that the policy implementing all QoS principles allows a Web content provider to guarantee the contractual SLA targets also in severe load conditions. Other algorithms lacking some QoS principles cannot be used for respecting SLA constraints although they provide acceptable performance for some load and system conditions.

The Research of Differentiated Service and Load Balancing in Web Cluster

“…However, because queueing model is based on the premise of Poisson arrival rate and exponential distribution of processing time, queueing model can not accurately describe the of HTTP traffic feature when the arrival rate and leave rate does not match(see [2,9]). Dynamic Partitioning (DynamicPart) algorithm is proposed by Casalicchio (see [1]). By feedback control, the back-ends is dynamically servicing different kinds of requests, which transforms a best-effort Web cluster into a QoS-enhanced system.…”

"Mecanismos de negociação no módulo de controle de admissão da arquitetura de servidor web com diferenciação de serviços (swds)"

“…Pesquisas recentes têm mostrado que a QoS também pode ser obtida em nível de aplicação. (ANDREOLINI et al, 2004) …”

WSARCH: Uma arquitetura para a provisão de web services com qualidade de serviço

“…Por isso são necessários algoritmos de balanceamento de carga, como sugerem os trabalhos de (Ho et al, 2004) e (Chen e Chen, 2004) , para permitir alta disponibilidade dos servidores, evitar a sobrecarga, além de possibilitar uma resposta rápida aos clientes. Outros trabalhos que merecem destaque nesta área, incluem (Pai et al, 1999), (Crovella et al, 1999), (Cherkasova e Phaal, 2002), (Eggert e Heidemann, 1999), (Chen e Mohapatra, 1999), (Blanquer et al, 2004), (Bhinder et al, 2004), (Andreolini et al, 2004). Todos, de uma forma geral abordam a problemática de se tratar a diferenciação de serviço no nível da aplicação, utilizando técnicas de balanceamento de carga, escalonamento, controle de admissão, middleware, etc.…”