Howto: Custom MonitorMBean ?

Question

Hi!
We are currently adopting JMX is the management and monitoring layer in our application.
As a starting point to my question, just take it given, that I can access several statistic values via a DynamicMBean.
What I want to do, is to monitor some of these values and have Notifications fired once thresholds are reached.
We have successfully built a prototype for this and everything seems to be working fine - as long as we stick to the Monitors delivered with JDK 6.
One thing that we need, but that does not come with the JDK is a special kind of GaugeMonitor - lets call it AverageMonitor. The AverageMonitor should be able, to monitor two adjanced attributes, say a "number of requests" and a "processing time in seconds". The basic idea, is that the value that is monitored, should be computed by the monitor. In the example given, I would like it to compute the number of requests/second .
I was expecting, that I could simply extend the GaugeMonitor and override a few "hooks" two put in any additionally logic needed. But looking at the code in javax.management.monitor, it seems like the JMX MonitorMBean is not designed this way. Maybe I am blind, or simply overlook something, but every method that might be a good entry point for my stuff has only package visibility. So do the inner classes that are used to store the data for every observed object.
The way I see it right now, I cannot build anything ontop of the given Monitor classes from javax.management.monitor. Instead it seems like I have to implement the whole MonitorMBean from scratch. Is this really so? Looking at all the things that are hidden in the javax.management.monitor.Monitor baseclass, this has become a rather scary idea. I really hope I am missing something here.
Taking a step back, I wonder if I am taking the wrong route here? Maybe there is another way to achieve my goals? But I do not want the components that are producing the numbers to also do the computation. The counters I want to monitor will probably change quite often and so I do not want the computation of any values, like the average in the example above, to be calculated on every update, but rather only when the monitor is looking at them.
Thanks for any hints or insights on this issue.
bye, Michael
Edited by: m_hess on Nov 24, 2009 8:15 AM - fixed typo

Answer 1

You understood correctly so far, but we are further down the road already. I have the numbers already available in a DynamicMBean. The problem is, that some of the bare numbers are not interesting. Take antother look at the given example, with the request time and the number of total requests. Both number might be somewhat interesting on their own, but the real information (given the example) is the average number of requests per second.
So what it boils down to is that I am not interested in the bare numbers provided by the mbean, but some aggregate form.
As I see it, I could in theory change the DynamicMBean implementation, so that it additionally exposes the calculated average. That way, I am back to a single value, which can easily be monitored by the standard classes. So in the end there will be some solution to this for sure.
But my initial question is the more burning one: Is there any simple way to implement a MonitorMBean or even better extend javax.management.monitor.Monitor? The problem with the Monitor class is, that it is HUGE and it is not really clear, what the hooks for any subclassing would be.
Thanks for your input!
Michael