Wednesday, February 27, 2008

JConsole in local mode and tomcat

After some debugging found that Jconsole will connect locally to a new MBeanServer created via ManagementFactory.getPlatformMBeanServer(). Tomcat will look for an existing MBeanServer and create one if needed - but this will be different than what jconsole uses.

The fix is 2 lines - benefit is that you can start tomcat normally, without any special flag, then connect with jconsole and inspect/modify settings. It looks like they use some signal or other form of communication on Linux, which opens a TCP port.

I'm not sure why someone would ever want to use MBeanServerFactory.findMBeanServer() and createMBeanServer. Sure, in the rarely used sandbox mode, if you want to strongly isolate apps it may be needed - assuming you want each untrusted app to have access to its own server, and grant it create mbean server rights.

Time to send a patch - long time since I haven't done that...