基于j2ee在分布式环境下的底层结构的自动动态配置的应用-------外文翻译.doc

Abstract: in order to achieve such dynamic adaptation, we need an infrastructure for automating J2EE application deployment in such an environment. This need is quite evident to anyone who has ever tried deploying a J2EE application even on a single application server, which is a task that involves a great deal of configuration of both the system services and application components.
Key words: j2ee; component; Distributed; Dynamic Deployment;
1 Introduction
In recent years, we have seen a significant growth in component-based enterprise application development. These applications are typically deployed on company Intranets or on the Internet and are characterized by high transaction volume, large numbers of users and wide area access. Traditionally they are deployed in a central location, using server clustering with load balancing (horizontal partitioning) to sustain user load. However, horizontal partitioning has been shown very efficient only in reducing application-related overheads of user-perceived response times, without having much effect on network-induced latencies. Vertical partitioning (e.g., running web tier and business tier in separate VMs) has been used for fault isolation and load balancing but it is sometimes impractical due to significant run-time overheads (even if one would keep the tiers on a fast local-area network) related to heavy use of remote invocations. Recent work [14] in the context of J2EE component based applications has shown viability of vertical partitioning in wide-area networks without incurring the aforementioned overheads. The key conclusions from that study can be summarized as follows:
• Using properly designed applications, vertical distribution across wide-area networks improves user-perceived latencies.
• Wide-area vertical layering requires replication of application components and maintaining consistency between replicas.
• Additional replicas may be deployed dynamically to handle new requests.
• Different replicas may, in fact, be different implementations of the same component based on usage (read-only, read-write).
• New request paths may reuse components from previously deployed paths.



摘要：为了实现广域网中符合工业标准基于组件的应用程序中动态的可适应性，我们需要一种框架来在这样的环境里自动化地配置J2EE 应用程序。这种需要对于哪怕在单一的应用程序服务器上尝试部署J2EE应用的人来说也显而易见，这种任务设计到大量的系统服务和应用组件的配置。
关键词：j2ee；动态配置；分布式；组件；
1 前言
近几年，我们已经看到基于组件的企业应用开发的显著增加。这种应用程序通常被部署在公司的内部网或者是因特网上，以高事务容量，大量的用户和覆盖范围广的访问为特征，它通常会被部署在中央区域，采用服务器集群来均衡负载从而支持用户下载。但是这种平均负荷的方法被证明只对减少应用转发的用户可以察觉的反应时间有效，而对于减少网络方面的延迟作用不大，垂直分割（例如…运行网络层和事务层在不同的虚拟机）被用于错误分离和均衡负荷，但是它是不符合实际的由于远程调运的大量使用显著地增加了运行时时间。最近的著作已经表明在广域网中利用垂直负荷而不引起前面所述的超时问题的可行性。那非研究的主要结论可以概括如下：
(1) 应用合适的应用程序，在广域网中的垂直负荷可以察觉的延迟。
(2) 广域垂直层需要复制应用层组件而且需要维持和原组件间的一致性。
(3) 新加的复制组件可以被动态配置以满足新的需要。
(4) 事实上，不同的复制组件可能会根据应用不同的方式实现相组件。
(5) 新的请求路径可以复用先前的组件配置路径。