Extracting Heap-dump (hprof) from Core-dump

Question

Currently I have a core-dump file and I would like to extract the heap-dump. Whatever I tried I always get the following error message:

god@heaven:~$ sudo /opt/java-MyApp/bin/jmap -dump:format=b,file=my-file.hprof /opt/java-MyApp/bin/java /home/god/tmp/core
[sudo] password for god: 
Attaching to core /home/god/tmp/my-app-core-dump from executable /opt/java-MyApp/bin/java, please wait...
Error attaching to core file: Doesn't appear to be a HotSpot VM (could not find symbol "gHotSpotVMTypes" in remote process)
sun.jvm.hotspot.debugger.DebuggerException: Doesn't appear to be a HotSpot VM (could not find symbol "gHotSpotVMTypes" in remote process)
    at sun.jvm.hotspot.HotSpotAgent.setupVM(HotSpotAgent.java:411)
    at sun.jvm.hotspot.HotSpotAgent.go(HotSpotAgent.java:305)
    at sun.jvm.hotspot.HotSpotAgent.attach(HotSpotAgent.java:156)
    at sun.jvm.hotspot.tools.Tool.start(Tool.java:191)
    at sun.jvm.hotspot.tools.Tool.execute(Tool.java:118)
    at sun.jvm.hotspot.tools.HeapDumper.main(HeapDumper.java:83)
    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:497)
    at sun.tools.jmap.JMap.runTool(JMap.java:201)
    at sun.tools.jmap.JMap.main(JMap.java:130)

If I try to open the core with gdb, it works like a charm:

gdb --core core
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[New LWP 11241]
[New LWP 11242]
[New LWP 11243]
[New LWP 11244]
[New LWP 11245]
...
[New LWP 23423]
[New LWP 30560]
[New LWP 11240]
Core was generated by `/opt/java-MyApp/bin/java -Djava.util.logging.config.file=/opt/MyAp'.
#0  0x0000003c838cc0a6 in ?? ()
[Current thread is 1 (LWP 11241)]
(gdb) 

From all stuff I have read, I should be sure to have the JVM installed on same path and version I had when core dump was done using {{gcore}}. Being done that all I need to do is call jmpa witht that exact jvm:

sudo $JVM_USED_WHILE_GCORE_HOME/bin/jmap -dump:format=b,file=$OUTPUT_HPROF_FILE $JVM_USED_WHILE_GCORE_HOME/bin/java $CORE_FILE_PATH

Is there something I'm missing? Why do I constatly get the "could not find symbol "gHotSpotVMTypes" in remote process" error message?

Johppah

Under gdb, can you find gHotSpotVMTypes symbol? – Avaavadavat

aren't all OpenJDK versions? Or what may I check? – Johppah

Type p gHotSpotVMTypes under gdb – Avaavadavat

I get: No symbol table is loaded. Use the "file" command. – Johppah

And if I do (gdb) file ~/Apps/jdk1.8.0_102/bin/java I get Reading symbols from ~/Apps/jdk1.8.0_102/bin/java...(no debugging symbols found)...done. – Johppah

gHotSpotVMTypes symbol is defined in libjvm.so (not in java launcher). It looks like libjvm.so referenced in coredump is missing or does not match the local version. – Avaavadavat

@Avaavadavat thanks, you lead me to the right direction, the problem was basically that java was being referred by a symlink, once I created the symlink locally I could extract the heapdump. – Johppah

Answer 1

The problem was fairly simple. The /opt/java-MyApp/bin/java path was a symlink, once I re-created the structure as I had on the machine used to generate the core-dump it worked like a charm. It seems the libraries are used by its canonical path.

Johppah