Java Heap Dump error - Metadata does not appear to be polymorphic

Question

I get this Stacktrace when trying to take a heap dump from a running Java process. What causes this and what do I have to do to make a proper heap dump?

Dumping heap to dump.bin ...
Exception in thread "main" java.lang.reflect.InvocationTargetException
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:483)
    at sun.tools.jmap.JMap.runTool(JMap.java:201)
    at sun.tools.jmap.JMap.main(JMap.java:130)
Caused by: java.lang.InternalError: Metadata does not appear to be polymorphic
    at sun.jvm.hotspot.types.basic.BasicTypeDataBase.findDynamicTypeForAddress(BasicTypeDataBase.java:278)
    at sun.jvm.hotspot.runtime.VirtualBaseConstructor.instantiateWrapperFor(VirtualBaseConstructor.java:102)
    at sun.jvm.hotspot.oops.Metadata.instantiateWrapperFor(Metadata.java:68)
    at sun.jvm.hotspot.memory.DictionaryEntry.klass(DictionaryEntry.java:71)
    at sun.jvm.hotspot.memory.Dictionary.classesDo(Dictionary.java:66)
    at sun.jvm.hotspot.memory.SystemDictionary.classesDo(SystemDictionary.java:190)
    at sun.jvm.hotspot.memory.SystemDictionary.allClassesDo(SystemDictionary.java:183)
    at sun.jvm.hotspot.utilities.HeapHprofBinWriter.writeClasses(HeapHprofBinWriter.java:942)
    at sun.jvm.hotspot.utilities.HeapHprofBinWriter.write(HeapHprofBinWriter.java:427)
    at sun.jvm.hotspot.tools.HeapDumper.run(HeapDumper.java:62)
    at sun.jvm.hotspot.tools.Tool.startInternal(Tool.java:260)
    at sun.jvm.hotspot.tools.Tool.start(Tool.java:223)
    at sun.jvm.hotspot.tools.Tool.execute(Tool.java:118)
    at sun.jvm.hotspot.tools.HeapDumper.main(HeapDumper.java:83)
    ... 6 more

Environment: CentOS 64 bit, Java OpenJDK Runtime Environment (build 1.8.0_31-b13) OpenJDK 64-Bit Server VM (build 25.31-b07, mixed mode)

Using ps to see the java version that is used:

/usr/lib/jvm/java-1.8.0-openjdk-1.8.0.31-1.b13.el6_6.x86_64/jre/bin/java

My first try was:

/usr/lib/jvm/java-1.8.0-openjdk-1.8.0.31-1.b13.el6_6.x86_64/bin/jmap  -dump:format=b,file=dump.bin 14984

That got me :

14984: Unable to open socket file: target process not responding or HotSpot VM not loaded
The -F option can be used when the target process is not responding

So I ran with the -F option

/usr/lib/jvm/java-1.8.0-openjdk-1.8.0.31-1.b13.el6_6.x86_64/bin/jmap -F -dump:format=b,file=dump.bin 14984

Answer 1

Ok, I found it.

I was running the jmap command as root, but I had to run as the user that started the java process.

In my case:

sudo -u robau ./jmap -dump:format=b,file=/tmp/dump.bin 14984

Seems to be related to this JDK bug: https://bugs.openjdk.java.net/browse/JDK-8075773