Byteman Plugin Revisited

A couple of months ago, I came across Byteman and liked it so much, I wanted to see how easy it would be to manage it, so I wrote a quick RHQ agent plugin prototype for it and blogged about it.

Since I had some time over Christmas, I decided to revisit that prototype and build it out further. The finished product can probably be considered a good 1.0 version of a fully featured RHQ Byteman plugin.

With this RHQ-Byteman integration, you can now do remote byte-code injection into any Java virtual machine that has a Byteman agent running inside of it. Simply write your Byteman rules, store them in one or more scripts and file-upload those scripts from your browser to the RHQ Server. The RHQ Server will then stream down those script files to the remote Byteman agent, which then injects the code directly in its Java virtual machine. It is extremely easy to run a VM with Byteman inside of it - all you need is to pass a -javaagent VM argument to Java when you start it; something like:

-javaagent:/opt/byteman/lib/byteman.jar=listener:true

The uses for this kind of thing are boundless - from tracing how long it takes for a Java method to execute to testing an application's fault tolerance by forcing test exceptions to be thrown. In the future, I plan on attempting to write an extension to the Byteman plugin to allow me to trace JDBC calls and create reports based on the data I get back. In fact, work on that has already begun; the bulk of the RHQ plugin code is already written, I just have to figure out how to write the proper Byteman rules to get it to do what I want. Once I complete this "JDBC Trace" RHQ agent plugin, I'll blog/demo it.

If you are interested in this new RHQ integration with Byteman, watch the flash demo.

Note that in order to finish this Byteman plugin, I had to add some additional capabilities within Byteman itself. The bulk of the changes manifested themselves as new API methods to the Byteman client - the "Submit" class. These new features allow Byteman to be easily managed, not just by RHQ, but by any management tool that wants to integrate with Byteman. I committed this new code to Byteman's SVN repository which should make these new features available in its next release. Because the new Byteman is not released yet, nor available in the JBoss maven repository, I placed the RHQ Byteman plugin code in its own git branch. Once the next Byteman version is released, I'll merge my code into RHQ's master branch.