JAR-less plugins for RHQ

Mazz has written a few times about the Custom-JMX plugin (funnily enough I did not find a newer post to link to), which is basically a plugin descriptor, that re-uses the classes from the base JMX plugin.

While this is very powerful, it has the small usability drawback of requiring to wrap the descriptor into a jar file to be recognized by the server (and the agents).

I have now implemented BZ 741682 which allows to deploy plugin descriptors only. For this to work

• the file needs to be called *-rhq-plugin.xml (e.g. foo-rhq-plugin.xml)
• the classes of the plugin need to already be present on the agent

The latter can be achieved by putting a depends directive into the descriptor:

<depends plugin="JMX" useClassed="true"/>

In the following example you see the bar-rhq-plugin.xml file picked up from the $SERVER/plugins directory
(the "drop-box") and placed into the plugins directory inside the app:

09:18:55,160 INFO  [PluginDeploymentScanner] Found plugin descriptor at 
    [/im/dev-container/plugins/bar-rhq-plugin.xml] and placed it at 
    [/im/dev-container/jbossas/server/default/deploy/rhq.ear/rhq-downloads/rhq-plugins/bar-rhq-plugin.xml]

Next is the transformation of this plugin descriptor into a jar file - if this is successful, the now obsolete plugin descriptor is removed.

09:18:55,403 INFO  [AgentPluginScanner] Found a plugin-descriptor at 
    [/im/dev-container/jbossas/server/default/deploy/rhq.ear/rhq-downloads/rhq-plugins/bar-rhq-plugin.xml],
    creating a jar from it to be deployed at the next scan
09:18:55,411 INFO  [AgentPluginScanner] Deleted the now obsolete plugin descriptor: true

At the next scan of the deployment scanner, the scanner will pick up this generated jar and deploy it like any other plugin:

09:19:26,470 INFO  [ProductPluginDeployer] Discovered agent plugin [bar-test]
09:19:26,474 INFO  [ProductPluginDeployer] Deploying [1] new or updated agent plugins: [bar-test]
09:19:26,656 INFO  [ResourceMetadataManagerBean] Persisting new ResourceType [bar-test:test(id=0)]...
09:19:29,344 INFO  [ProductPluginDeployer] Plugin metadata updates are complete for [1] plugins: [bar-test]

The last step would then be to run plugins update on the agent to get this new plugin from the server and to deploy it into the agent.