JMX, SNMP, Java, etc...

Although it might not be a very good idea to define your management model based on how it will be displayed by a given GUI, such as that provided by JConsole or VisualVM, I believe it is nonetheless interesting to explore the various ways in which a complex type such as a Map<String,Integer> could be modeled and exposed through an MXBean attribute.

... while working on uncommitted changes.

Sometimes when you are working on a fix - or an RFE, you'd like to sync-up with your parent's repository and pull any changes it contains without having to commit your own work in progress. Here is my own recipe - direct from my mercurial cookbook.

Jean-Francois Denise has just contributed a very interesting source add-on contribution to Project OpenDMK. It is composed of two small java classes which provide a generic RESTful access to MBean attributes.

Recently I was asked how to do "registerMBean" in a remote JVM, from a remote JMX client. The MBeanServerConnection doesn't expose any registerMBean method, and for good reasons.

After several years of resistance, I have finally surrendered to modernity: last week I bought a mobile phone.

... so I thought I'd drop a line. I have just uploaded a small set of slides of a high level presentation of project OpenDMK on the project's home page.

JMX is a wonderful tool to monitor and troubleshoot running applications. The new JDK 6 Attach API makes it very easy to attach to a running Java process, and start a JMX agent that will expose monitoring and configuration data to JMX consoles - like JConsole. However, there are some situations where you wish to start a JMX agent on demand, explore the monitoring data or diagnose the probable cause of an observed problem, and then close your JMX agent, leaving the application just how you found it.

In this post, I will discuss a means by which you can upload and start such a remotely stoppable JMX agent. Here is how.

The source code for OpenJDK is now available in Mercurial repositories. These repositories are organized into mercurial forests. If you are eager to work on the OpenJDK code, you will want to install the forest extension for Mercurial. Here is how I did it on my windows test machine.

In his blog, Ingo Rockel posted about a nice Thread Dump plugin for JConsole. Out of curiosity, I decided to give it a try.

This article exposes a proxying technique that can be used to adapt between two different protocols: one that is used on the server side, and one that we want to use on the client side. More to the point, this technique can be used to work around an annoying interoperation problem that can show up when exposing Model MBeans through an IIOP connector.

This post explains how you can configure your Java application to export a single port using JMX RMI Connector Server over SSL. This is particularly useful when your application is located behind a firewall, because you will only need to let through a single port. However, using a single port when SSL is enabled requires a little care, because it can only work if the same RMI Socket Factories are used everywhere: indeed the same port cannot be shared by two different RMI Socket Factories. So at the risk of boring you, here is my third post on the subject.

Dmitri Maximovich has written an excellent article about how to monitor JVM memory using MRTG.

I recently received a question from a member of the Java community asking for advises on how to implement a trap sending service for a highly multi-threaded application.

Here is an example/test which shows that the SnmpAdaptorServer from Project OpenDMK can be used. The example also allowed me to find a bug.