JVM MONITORING

Monitoring the JVM

JDK 5 includes a number of tools that are useful for monitoring the JVM. Documentation for these tools is available from the Sun website. For JDK's prior to 5, Sun provides the jvmstat tools .

The most useful tool is jconsole. Details on using jconsole are provided in the Administration section of the Resin documentation.

jconsole

win> ./httpd.exe -Dcom.sun.management.jmxremote unix> bin/httpd.sh -Dcom.sun.management.jmxremote  ... in another shell window ... win> jconsole.exe unix> jconsole Choose Resin's JVM from the "Local" list.

jps and jstack are also useful, providing a quick command line method for obtaining stack traces of all current threads. Details on obtaining and interpreting stack traces is in the Troubleshooting section of the Resin documentation.

jps and jstack

# jps 12903 Jps 20087 Resin # jstack 20087 Attaching to process ID 20087, please wait... Debugger attached successfully. Client compiler detected. JVM version is 1.5.0-beta2-b51 Thread 12691: (state = BLOCKED)  - java.lang.Object.wait(long) (Compiled frame; information may be imprecise)  - com.caucho.util.ThreadPool.runTasks() @bci=111, line=474 (Compiled frame)  - com.caucho.util.ThreadPool.run() @bci=85, line=423 (Interpreted frame)  - java.lang.Thread.run() @bci=11, line=595 (Interpreted frame) Thread 12689: (state = BLOCKED)  - java.lang.Object.wait(long) (Compiled frame; information may be imprecise)  - com.caucho.util.ThreadPool.runTasks() @bci=111, line=474 (Compiled frame)  - com.caucho.util.ThreadPool.run() @bci=85, line=423 (Interpreted frame)  - java.lang.Thread.run() @bci=11, line=595 (Interpreted frame) ...