If you instrument a tomcat 6.0.x running JVM >= 1.6.0_u16 and -Dcom.sun.management.jmxremote.port is specified, tomcat hangs right after loading the agent properties.
Foglight instrumentation has a conflict with Sun jmxremote option.The conflict exists with -Dcom.sun.management.jmxremote or -Dcom.sun.management.jmxremote.port and related options. The issue is a class loading problem with Sun management agent. It should be noted that the problem may exist in previous version of JDK also not just > 1.6.0_16. In previous versions of JDK, the agent starts up but with the wrong main class where as in newer JDK, the agent startup itself stalls making it more obvious.
The solution is to use the -Dquest.agent.mainclass option setting it to the main class of the appserver.
refer case: 798863