How to automatically get thread dumps from tomcat

Question

We had some issues of thread pile ups with production tomcat server so I wanted to setup some cron to to periodically check thread dumps and send alert email if something is wrong. To do this we need to take thread dumps in file from shell script but I am unable to do that. From shell I can issue KILL -3 <PID> at periodic intervals but the problem is that dump goes to catalina.out which contains GBs of data because of which pulling out only thread dump is painful process. Some discussion threads suggested usage of "jstack" and redirect output to a file but that also is not working and giving this error:

-bash-3.2# java -version
java version "1.6.0_26"
Java(TM) SE Runtime Environment (build 1.6.0_26-b03)
Java HotSpot(TM) 64-Bit Server VM (build 20.1-b02, mixed mode)
-bash-3.2# uname -a
Linux ip-10-130-225-20 2.6.16.33-xenU #2 SMP Wed Aug 15 17:27:36 SAST 2007 x86_64 x86_64 x86_64 GNU/Linux

-bash-3.2# sudo /usr/java/jdk1.6.0_24/bin/jstack -F 15668
Attaching to process ID 15668, please wait...
Debugger attached successfully.
Server compiler detected.
JVM version is 19.1-b02
Deadlock Detection:

No deadlocks found.

Thread 8183: (state = BLOCKED)
Error occurred during stack walking:
sun.jvm.hotspot.debugger.DebuggerException: sun.jvm.hotspot.debugger.DebuggerException: get_thread_regs failed for a lwp
    at sun.jvm.hotspot.debugger.linux.LinuxDebuggerLocal$LinuxDebuggerLocalWorkerThread.execute(LinuxDebuggerLocal.java:152)
    at sun.jvm.hotspot.debugger.linux.LinuxDebuggerLocal.getThreadIntegerRegisterSet(LinuxDebuggerLocal.java:466)
    at sun.jvm.hotspot.debugger.linux.LinuxThread.getContext(LinuxThread.java:65)
    at sun.jvm.hotspot.runtime.linux_amd64.LinuxAMD64JavaThreadPDAccess.getCurrentFrameGuess(LinuxAMD64JavaThreadPDAccess.java:92)
    at sun.jvm.hotspot.runtime.JavaThread.getCurrentFrameGuess(JavaThread.java:256)
    at sun.jvm.hotspot.runtime.JavaThread.getLastJavaVFrameDbg(JavaThread.java:218)
    at sun.jvm.hotspot.tools.StackTrace.run(StackTrace.java:76)
    at sun.jvm.hotspot.tools.StackTrace.run(StackTrace.java:45)
    at sun.jvm.hotspot.tools.JStack.run(JStack.java:60)
    at sun.jvm.hotspot.tools.Tool.start(Tool.java:221)
    at sun.jvm.hotspot.tools.JStack.main(JStack.java:86)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
    at java.lang.reflect.Method.invoke(Method.java:597)
    at sun.tools.jstack.JStack.runJStackTool(JStack.java:118)
    at sun.tools.jstack.JStack.main(JStack.java:84)
Caused by: sun.jvm.hotspot.debugger.DebuggerException: get_thread_regs failed for a lwp
    at sun.jvm.hotspot.debugger.linux.LinuxDebuggerLocal.getThreadIntegerRegisterSet0(Native Method)

This bug seems to be open with java team.

Any other suggestion to intelligently take and analyze thread dumps? Or script to parse huge catalina.out and get just thread dumps out of it?

Answer 1

Another option could be JMX - ThreadMXBean. This was discussed at SO question How do I create a thread dump via JMX?

Answer 2

One quick way I figured out was (mis)using javamelody. We use it to monitor various aspects of application and it also provides visual & usual ways to look at current threads so I wrote small shell script to hit "http://IP:PORT/SERVICE/monitoring?part=threadsDump" every minute and dump response in a file. If response contains any blocked thread script will take thread dumps every 5 seconds. This helps upto some extent but when problem worsens and server stalls, javamelody also stop responding.