- 學位論文
有效率支援Web叢集系統之QoS的核心機制
A Kernel Mechanism for Efficiently Supporting Quality of Service in Web Cluster System
摘要
由於網際網路的爆炸性成長及來自世界各地遽增的服務需求，因此，由一台前端伺服器與多台後端伺服器所組成的叢集式網頁伺服器，已成為一個具有成本效益的解決方案，能夠同時處理大量的服務需求。而現今Web-based服務在網際網路上佔據極大的比例，為了在叢集式網頁伺服器上支援端對端服務品質(QoS)，設計一個能提供差異性服務且提供多樣性服務的叢集式網頁伺服器是非常重要的，並且能夠在系統超載的時候給予重要的請求(如下單、購物的請求)較妥善的處理以避免商業收入上的損失。此外，現今網頁伺服器常常處理多樣性的服務像是動態網頁、資料庫處理或是影音串流服務等等。因此，叢集式網頁伺服器必須以適當的機制加以強化並能夠提供端對端服務品質與採用智慧型的服務需求分派策略以支援多樣性的服務請求。 在本論文中，我們設計與實作一個核心層級的Web-based服務品質機制，能夠在我們的LVS-CAD平台上有效地針對不同請求達成差異性服務。同時，我們也提出了兩個新的內容感知需求分配策略(Content-Aware Request Distribution Policies)，稱為LARD/RC與GCAP，它們可以使叢集式網頁伺服器在同質性環境或是異質性環境下，皆可有效地支援多樣性服務的封包分配。 實驗結果證明，在LVS-CAD平台上搭配我們的Web-based服務品質機制，在系統超載時適當丟棄一些較不重要的請求，能夠確保所有的高優先權請求皆能符合SLA (Service level agreement)。另外我們所提出的LARD/RC與GCAP策略，在同質性環境下可以分別比LARD/R與CAP提昇110.43%與83.54%的效能，而在異質性環境下則可以分別比LARD/R與CAP提昇123.27%與47.34%的效能。 關鍵字：叢集式網頁伺服器、服務品質 (QoS)、內容感知需求分配
並列摘要
Due to the explosive growth of the Internet and increasing service demands from all around the world, the cluster-based system that consists of one request-dispatching server and several request-handling servers has become a cost-effective way to serve the huge amount of service demands. Nowadays, Web-based services have occupied a great proportion of the Internet services. In order to support end-to-end Quality of Service in Web clusters, it’s essential to design a Web cluster that can provide differentiated services to various requests and treat important requests such as billing and shipping requests with preferred order to avoid losing of business revenue. Besides, Web servers also have to handle more complex types of requests since requests from clients may be mixed with dynamic Web pages, database processing, or multimedia stream data. Therefore, a Web cluster should be enhanced with some mechanisms to provide end-to-end QoS and designed with intelligent request dispatching policies for supporting various types of service requests. In this thesis, we have designed and implemented a kernel-level Web-based Quality of Service (WQoS) mechanism that could efficiently support differentiated services when serving various types of Web requests in our LVS-CAD Web cluster. We have also proposed two new content-aware request distribution policies named Locality-Aware Request Distribution with Replication and Classification (LARD/RC) and Grouped Client-Aware Policy (GCAP) to dispatch requests efficiently in Web clusters providing multiple types of services and running in homogeneous or heterogeneous environments. Experimental results demonstrate that the LVS-CAD Web cluster with our proposed Web-based QoS mechanism can ensure all requests with high priority to conform to Service Level Agreement (SLA) by dropping acceptable percentage of requests with minor importance during the situation of system overloaded. Besides, our proposed LARD/RC and GCAP policies can perform 110.43% and 83.54% better than the well-known content-aware LARD/R policy and CAP policy respectively in a homogeneous environment and outperform the LARD/R policy and CAP policy by 123.27% and 47.34% respectively in a heterogeneous environment. Keywords: Web Cluster, Quality of Service, Content-aware Request Distribution
參考文獻
延伸閱讀
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