6.2. Plug-in Facets

This facet provides basic availability checking - is a managed resource up or down? When the plug-in container needs to know if a resource is running or not, it will ask the resource component's availability facet. Unlike the other facets, the AvailabilityFacet is required to be implemented by all resource components. You are forced to implement it because the ResourceComponent interface extends the AvailabilityFacet. You can optionally use the asynchronous availability collector to perform the avail checking.

This facet provides the ability for a resource component to modify the configuration of the actual managed resource. When a resource component implements this facet, it is saying it has the capability to get the current configuration of the managed resource as well as be able to change it. As an example, the JBoss AS Data Source Service resource component implements the ConfigurationFacet because it can report back to the user what the current settings are of that data source (e.g. its JDBC driver, its JNDI name, its connection pool size, etc) and it can allow the user to change those settings.

Resources may have content associated with them including deployed software or software parts and other content. This system can be used to inventory these software parts and to install and remove them. Deployed content can be EARs and WAR applications or libraries and deployment files on JBoss EAP. Plug-ins can support arbitrary types of content with this system.

Resources may have additional files (aka "content") associated with it - configuration files, deployment files, etc. Those resources that have associated content can implement the ContentFacet to help create, delete and manage that content.

This facet should be implemented by the ResourceDiscoveryComponent class for types of resources that can be manually added to inventory via the JBoss ON GUI. In addition, the corresponding server or service elements in the plug-in descriptor must include the supportsManualAdd="true" attribute. Manual add can be a useful capability when a particular Resource cannot be auto-discovered for some reason.

This facet exposes the capability for the component to collect measurement data from the managed resource and to report that data back to the server. For a measurement facet to work, the plug-in must define one or more metric definitions for the resource component's resource type in the plug-in descriptor. The resource component does not have to concern itself with how to schedule measurement collections and when it should collect the data. The only thing the MeasurementFacet requires the resource component to do is go out to the actual managed resource and collect the requested data. The plug-in container will manage all measurement collection schedules and will only call into the resource component's MeasurementFacet when the time is appropriate and it will only ask for the metrics that need to be collected at that time.

The measurement facet is what provides the graphs of measurement data that you see in the JBoss ON GUI Console.

This facet allows the resource component to perform operations (aka control actions) on the managed resource itself. This allows, for example, the JBoss AS Server resource component to provide the capability to start and stop the JBoss AS server. Other examples of operations are being able to clear a connection pool for a data source, or ask a resource to empty a data cache. Whatever the managed resource can be told to do, a resource component can expose that as an operation to the JBoss ON user.

Some resource components can support the creation and deletion of child resources (for example, a resource component representing the JBoss AS server can create and delete JBoss AS data source services by creating and deleting *-ds.xml files). This facet exposes this functionality.

To support managed resources, there is some data that support organizations might wish to know about regarding a managed resource, such as the contents of its log files, data files, and configuration files. The SupportFacet will provide a hook into this "support and maintenance" view of the managed resource.