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Chapter 1. An Overview of JBoss ON Plug-ins
A plug-in makes an application more useful in a specific kind of way. It is a way of providing new functionality or more options for existing functionality. In JBoss ON, there are two categories of plug-ins, depending on what functionality needs to be created: server-side plug-ins and agent plug-ins. JBoss ON has a very simple and tightly integrated framework for deploying new plug-ins, which makes it relatively easy to extend JBoss ON to do a specific, custom task. Almost any subsystem or functionality in JBoss ON can be expanded and customized by writing additional plug-ins. This guide is an introduction to how to write and implement plug-ins in JBoss ON.
1.1. Extending JBoss ON: Plug-ins Defined
JBoss ON follows a hub and spoke approach with a server at its heart. The agents are deployed locally on resources and interact with the resources, as well as the JBoss ON server. The server (or cluster of servers) processes data coming in from agents. The data are stored in a database connected to the server. Users can look at the data and trigger operations through a web-based GUI on the server.
Figure 1.1. JBoss ON Architecture
A plug-in defines what features it is using and then it contains the code (or API) necessary carry out whatever features or operations it has defined. In JBoss ON, a plug-in is targeted to work on either a server or on an agent.
Server-side plug-ins relate to any operation or task that is performed by the server. This includes alerting and notifications, managing content and packages, setting GUI appearance and functionality, and integrating JBoss ON information with other applications. A server-side plug-in is first identified by the server subsystem which it is associated with, and then with its functionality.
Agent plug-ins are used for any task that relates to resources, primarily managing inventory (by defining resource types) and configuring monitoring. An gent plug-in, then, is associated purely by its resource type.
There are some similarities between server-side and agent plug-ins structurally.
- Every plug-in is packaged as a JAR file.
- Every plug-in has a required XML file, the plug-in descriptor, which defines all of the plug-in capabilities.
- Every plug-in contains compiled Java files which contain the code necessary to perform all of the actions defined in the descriptor.
- Plug-ins run inside a plug-in container, which is the entity that directly interacts with the plug-ins and starts and stops all plug-ins.
- All custom plug-ins are deployed to the JBoss ON server. Server-side plug-ins are propagated across the high availability cloud to all of the other servers, while agent plug-ins are made available through the server for the agents to download.
