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 Infrastructure for Automatic Dynamic Deployment Of J2EE Application in Distributed Environments

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. Applying intelligent monitoring [6] and AI planning [2, 12] techniques in conjunction with the conclusions of that study, we see a potential for dynamic adaptation in industry-standard J2EE component-based applications in wide area networks Through deployment of additional application components dynamically based on active monitoring. However, 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. For example one has to set up JDBC data sources, messaging destinations and other resource adapters before application components can be configured and deployed. In a wide area deployment that spans multiple server nodes, this proves even more complex, since more system services that facilitate inter-node communications need to be configured and started and a variety of configuration data, like IP addresses, port numbers, JNDI names and others have to be consistently maintained in various configuration files on multiple nodes. This distributed deployment infrastructure must be able to: • address inter-component connectivity specification and define its effects on component configuration and deployment, • address application component dependencies on application server services, their configuration and deployment, • provide simple but expressive abstractions to control adaptation through dynamic deployment and undeployment of components, • enable reuse of services and components to maintain efficient use of network node