Architecture Web Application Tiers

9 Cluster Architectures 9-1 9 Cluster Architectures This following sections describe alternative architectures for a WebLogic Server cluster: ■ Section 9.1, Architectural and Cluster Terminology ■ Section 9.2, Recommended Basic Architecture ■ Section 9.3, Recommended Multi-Tier Architecture ■ Section 9.4, Recommended Proxy Architectures ■ Section 9.5, Security Options for Cluster Architectures

9.1 Architectural and Cluster Terminology

This section defines terms used in this document.

9.1.1 Architecture

In this context the architecture refers to how the tiers of an application are deployed to one or more clusters.

9.1.2 Web Application Tiers

A Web application is divided into several tiers that correspond to the logical services the application provides. Because not all Web applications are alike, your application may not utilize all of the tiers described below. Also keep in mind that the tiers represent logical divisions of an applications services, and not necessarily physical divisions between hardware or software components. In some cases, a single machine running a single WebLogic Server instance can provide all of the tiers described below. ■ Web Tier The Web tier provides static content for example, simple HTML pages to clients of a Web application. The Web tier is generally the first point of contact between external clients and the Web application. A simple Web application may have a Web tier that consists of one or more machines running Apache, Netscape Enterprise Server, or Microsoft Internet Information Server. ■ Presentation Tier The presentation tier provides dynamic content for example, servlets or Java Server Pages to clients of a Web application. A cluster of WebLogic Server instances that hosts servlets andor JSPs comprises the presentation tier of a Web application. If the cluster also serves static HTML pages for your application, it encompasses both the Web tier and the presentation tier. 9-2 Using Clusters for Oracle WebLogic Server ■ Object Tier The object tier provides Java objects for example, Enterprise JavaBeans or RMI classes and their associated business logic to a Web application. A WebLogic Server cluster that hosts EJBs provides an object tier.

9.1.3 Combined Tier Architecture