Easy: engineering high availability QoS in wServices

摘要

Developing and administrating distributed applications is complex. Frameworks, hiding the distribution hurdles through encapsulation were proposed, but their acceptance by the industry has been limited. The main reason is the difficulty to provide a simple interface to meet a wide range of application types. In this paper we address the functional services provided over the Web (henceforth, wServices). Examples of wServices are grid services. These typically small software components are often developed under tight budget and timeframe constraints. A wService may be deployed on different platforms and provide different QoS guarantees. With the advent of e-business, wServices become an important type of distributed applications. We claim that narrowing the view to this type of applications allows providing a simple interface. Furthermore, we show that good performance can be achieved if wService developers provide simple tuning parameters as part of a wService package. In our Easy model, platform and QoS specifics are decoupled from wService development costs. In addition we aim at increasing automation of wService deployment on various platforms and for different QoS. The focus of this paper is on performance aware high availability, achieved through wService cloning and replication of its state. In our philosophy, wService developers are aware of potential cloning and replication but not of the mechanisms that provide it. We demonstrate the feasibility of Easy through a prototype with an automatically deployed TomCat Web Container. Easy clones TomCat and replicates its states. We show that this automated process imposes only slight performance degradation compared to a manual one.