Monday, May 18, 2009

Supporting Events In Your Custom Plugin

This blog is in response to a question from user "earthling" about my Correlating Events with Jopr blog entry.

"How do i use this feature [Events] in a custom plugin?"

It's easiest if you just copy the code from one plugin to your custom plugin. It isn't that much code.

First, you need to declare that your plugin's custom resource type supports events. Look at how the JBossAS plugin descriptor does this - you can probably copy the <plugin-configuration>...<c:group name="event" displayName="Events"> section verbatim.

Then, your custom ResourceComponent subclass needs to add an event poller to the plugin container. You can do this within your start() method, as the JBossASServerComponent does, like this:

public void start(ResourceContext context) throws Exception {
this.logFileEventDelegate = new LogFileEventResourceComponentHelper(this.resourceContext);

Note that the "LogFileEventResourceComponentHelper" class is new that Ian added after 2.2. So, you'll have to build trunk/HEAD to be able to use it. If you have 2.2 or less, just grab that class and use it in your plugin (or at least copy-n-paste its code).

In your components stop() method, you need to remove the event poller, too:

public void stop() {

Once your resource has started, it will start emitting logs that the Jopr Server will show you! You get all the event functionality by adding that little bit of metadata and code. Of course, the example above assumes your events come from log4j log files. But events can come from anywhere. For example, the Windows platform plugin component can emit events from the Windows Events subsystem and Greg Hinkle has updated the Linux plugin component so that it emits syslog messages from his Linux box (he should probably check that in soon :).