Hey Bobby,
Take this with a grain of salt. From what I've read, you may see that
NPE when attaching to a JVM that has exhausted the heap.
You state you ran jstack against both hung instances with the same
result and that when you restarted the first time, it immediately hung
again.
Are you 100% certain all processes from the first instance were down and
you didn't re-attach to those? Seems really odd that the server
would just hang immediately after a restart with the same NPE. Just a
sanity check :)
Bobby Bissett wrote:
> Hi all,
>
> One of our GF 3.1.2 servers just hung, and after a restart immediately
> hung again. Running jstack both times gives us an NPE that I haven't
> seen before. Does anyone know what this might mean? (Google doesn't
> seem to know much about it except for other examples of it.)
>
> Thanks,
> Bobby
>
> -bash-3.2# /jdk1.6.0_31/bin/jstack -F 21102 >
> /home/robert.bissett/jstack.out2
> Attaching to process ID 21102, please wait...
> Debugger attached successfully.
> Server compiler detected.
> JVM version is 20.6-b01
> java.lang.NullPointerException
> at
> sun.jvm.hotspot.oops.InstanceKlass.computeSubtypeOf(InstanceKlass.java:426)
> at sun.jvm.hotspot.oops.Klass.isSubtypeOf(Klass.java:137)
> at sun.jvm.hotspot.oops.Oop.isA(Oop.java:100)
> at
> sun.jvm.hotspot.runtime.DeadlockDetector.print(DeadlockDetector.java:93)
> at
> sun.jvm.hotspot.runtime.DeadlockDetector.print(DeadlockDetector.java:39)
> at sun.jvm.hotspot.tools.StackTrace.run(StackTrace.java:52)
> 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)