The following is a short introduction for each WebSphere® Network Deployment runtime component and their functions:
The Deployment Manager is part of an WAS Network Deployment V5.x installation. It provides a central point of administrative control for all elements in a distributed WebSphere® cell. Deployment Manager is a required component for any vertical or horizontal scaling and there exists only one specimen of it at a time.
The Node Agent communicates directly with the Deployment Manager, and is used for configuration synchronization and administrative tasks such as stopping/starting of individual appservers and performance monitoring on the application server node.
An appserver in WebSphere® is the process that is used to run your servlet and/or EJB-based applications, providing both Web container and EJB container.
While the Web server is not strictly part of the WebSphere® runtime, WebSphere® communicates with your Web server of choice: IBM® HTTP Server powered by Apache, Microsoft® Internet Information Server, Apache, Sun ONE Web server, and Lotus® Domino via a plug-in. This plug-in communicates requests from the Web server to the WebSphere® runtime.
The embedded HTTP transport is a service of the Web container. An HTTP client connects to a Web server and the HTTP plug-in forwards the requests to the embedded HTTP transport. The communication type is either HTTP or HTTPS between the plug-in and the embedded HTTP transport.
Although the embedded HTTP transport is available in any WAS to allow testing or development of the application functionality prior to deployment, it should not be used for production environments.
The JMS server was introduced with WAS V5 (all versions except WebSphere® Express). The JMS server is a complete messaging server that supports point-to-point and publish/subscribe styles of messaging.
The administrative service runs within each WAS Java virtual machine (JVM.) Depending on the version installed, there can be administrative services installed in many locations. In WAS V5.0 and higher, the administrative service runs in each appserver. In a Network Deployment configuration, the Deployment Manager, Node Agent, application server(s), and JMS server all host an administrative service. This service provides the ability to update configuration data for the application server and its related components.
The WebSphere® Administrative Console provides an easy-to-use, graphical "window" to a WebSphere® cell, runs in a browser, and connects directly to a WebSphere® V5.1 server or to a Deployment Manager node that manages all nodes in a cell.
The configuration repository stores the configuration for all WAS components inside a WebSphere® cell. The Deployment Manager communicates changes in configuration and runtime state to all cell members through the configuration repository.
A cell is a set of Application Servers managed by the same Deployment Manager. Some appserver instances may reside on the same node, others on different nodes. Cell members not necessarily run the same application.
A server cluster is a set of appserver processes. They run the same application but usually on different nodes. The main purpose of clusters is load balancing and failover.
Figure 1-2 WebSphere® configuration with Java clients and Web clients
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