debugging JBoss 100% CPU usage

Question

Originally posted on Server Fault, where it was suggested this question might better asked here.

We are using JBoss to run two of our WARs. One is our web app, the other

Answer 1

This typically happens with runaway code or unsafe thread access to hashmaps. A simple thread dump (kill -3, as @disown says, or ctrl-break in a windows console) will reveal this problem.

Since you're unable to reproduce it using tests I think it smells like a concurrency issue; it's usually hard to make test scripts behave sufficiently random to catch issues of this type.

I normally try to make it standard operating procedure to do thread-dumps of any JVM that is restarted due to operational anomalies, and it's really a requirement to catch those once-a-month things.