Providing fault-tolerant execution of web-service-based workflows within clouds

Abstract

With a variety of services rapidly evolving at all architec-tural levels of cloud computing, there is an increasing de-mand for a standardized way to coordinate their interac-tions. Business process management, that is, more general, the management of Web-service–based workflows, could sat-isfy this demand and, indeed, first corresponding offerings have gained instant popularity. While from a functional per-spective, these Platform-as-a-Service (PaaS) solutions are al-ready quite mature, their support for fault tolerance is still very limited, making them inapplicable for critical tasks. Concerning the deficiencies of currently existing systems, this paper presents a practical solution for executing criti-cal Web-service–based workflows, particularly within clouds, in a fault-tolerant, highly available and highly configurable manner. We achieve this by actively replicating workflows as well as Web services in a combined architecture, reusing existing standard systems and coordination services. By providing an automated transformation tool, replication is realized transparently to existing systems and workflows. Measurements show that our proposed architecture achieves lower response times than existing systems and that the in-tegration of a coordination service imposes only moderate costs, while simplifying the implementation and leading to a dynamically adaptable solution. 1