資訊網服務容錯系統之研究

Abstract

資訊網服務(Web Service)是目前全球資訊網之分散式計算平台的重要發展技術，其應用可以包括電子商務之企業應用技術、系統整合的中介軟體及網格服務(Grid Service)等。資訊網服務除了具備簡單明瞭的XML純文字型態內容以及跨平台與跨程式語言的優點外，高度的延展性與防火牆的穿透性更是其專屬特色。另外為了提高系統的穩定度與可靠度，資訊網服務平台的容錯機制是不可或缺的重要技術，而目前資訊網服務對於容錯的探討僅有規範客戶端與伺服端之間的訊息傳輸。因此，容錯機制對於目前的資訊網服務而言，是迫切需要的。

本論文提出FT-SOA(Fault Tolerant – Service Oriented Architecture)系統架構，並依此架構發展出一套資訊網服務容錯系統。此系統針對服務提供者的伺服端部份，提出運用主體-備份(Primary-Backup)、動態投票(Dynamic Voting)及選集理論(Quorum-Based)等重複技術的容錯策略來架構伺服端的資訊網服務容錯平台，並提供可讓服務提供者建置的服務直接佈署於上，就可以具有完備的容錯功能。另外針對服務仲介者的伺服端部份，提出運用選集理論的容錯策略來提供資訊網服務的容錯目錄服務，同時因選集的特性又使其兼具負載平衡及支援動態呼叫(Dynamic Invocation)的優越功能。

本論文並制定資訊網服務容錯訊息(Web Service Fault Tolerant Messaging: WSFTM)，來做為此類容錯平台間訊息溝通的方式。因此，透過本系統提供的規範與功能可提高資訊網服務整體的可用度，並且讓服務需求者及服務提供者之間的資訊網服務連結能更快速。Recently, Web Service has become one of the important techniques for distributed computing of World Wide Web, and it could apply to e-business application, middleware of system integration, and Grid Service, etc. Web Service not only has a lightweight and simple XML-based protocol that is designed to exchange structured and typed information on the web, but it still has the characteristics of highly extension and transparency of firewall. Besides, in order to improve reliability and stability of systems, some standards or mechanisms for Web Service are necessary. But, base on our preliminary investigation, we conclude that current Web Service is lack of mechanism to build a fault tolerant system in the parts of service provider and service broker. So, to possess a highly availability system, fault tolerant mechanism is essential for Web Service. We propose FT-SOA system architecture in order to address the fault tolerant issue and discuss how to design in general SOA system. And according to it, we develop FT-Web Service System. In the part of service providers, we construct the FT Platform facilitates general Web Service to deploy and execute using three fault tolerant strategies include Primary-Backup, Dynamic Voting, and Quorum-Based. In the part of service brokers, we construct the FT Directory Service to improve its availability using the fault tolerant strategy of Quorum-Based, and by the advanced characteristics of Quorum, it also provides capabilities of load balance and dynamic invocation. Besides, we propose Web Service Fault Tolerant Messaging (WSFTM) to become the communication mechanism between the fault tolerant systems. So, according to this design, our system makes the binding between system requestors and system providers faster.