Can't dump heap on java process

Question

I have a java process which I want to debug. The problem with it is that it has too many open connections, so running jmap fails because it can't connect to process. Running jmap -F produces the next error:

Attaching to process ID 1772, please wait...
sun.jvm.hotspot.debugger.NoSuchSymbolException: Could not find symbol "gHotSpotVMTypeEntryTypeNameOffset" in any of the known library names (libjvm.so, libjvm_g.so, gamma_g)
        at sun.jvm.hotspot.HotSpotTypeDataBase.lookupInProcess(HotSpotTypeDataBase.java:388)
        at sun.jvm.hotspot.HotSpotTypeDataBase.getLongValueFromProcess(HotSpotTypeDataBase.java:369)
        at sun.jvm.hotspot.HotSpotTypeDataBase.readVMTypes(HotSpotTypeDataBase.java:102)
        at sun.jvm.hotspot.HotSpotTypeDataBase.<init>(HotSpotTypeDataBase.java:85)
        at sun.jvm.hotspot.bugspot.BugSpotAgent.setupVM(BugSpotAgent.java:568)
        at sun.jvm.hotspot.bugspot.BugSpotAgent.go(BugSpotAgent.java:494)
        at sun.jvm.hotspot.bugspot.BugSpotAgent.attach(BugSpotAgent.java:332)
        at sun.jvm.hotspot.tools.Tool.start(Tool.java:163)
        at sun.jvm.hotspot.tools.HeapDumper.main(HeapDumper.java:77)
        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.jmap.JMap.runTool(JMap.java:179)
        at sun.tools.jmap.JMap.main(JMap.java:110)
Debugger attached successfully.

What can be the problem? Can it be solved without restarting the process (It is possible the bug will disappear after restarting so I want to avoid it).

Answer 1

What can be the problem? Can it be solved without restarting the process (It is possible the bug will disappear after restarting so I want to avoid it).

At the risk of stating the obvious ...

If you cannot connect with the debugger because too many connections are open, that is probably also at the root of the bug you are trying to find.

Try using an OS-level utility to find out what files / sockets / etc the process currently has open. That you give you some clues to tell you where to start looking. If that's not enough, search through your codebase for all places where files / sockets are opened, and examine them to make sure that they have an enclosing try / finally that will always close the file / socket.

Answer 2

Can you use visualvm from the Sun 6 JDK to connect? It uses a different method and allows you to learn a lot - which may be enough - but is not a debugger.

Answer 3

For Sun Jvm : You can try new

HotSpotDiagnostic().dumpHeap("d:\\HeapDump1",true);

If HotSpotDiagnostic class is not visible at compile time,then You can copy the rt.jar which has the HotSpotDiagnosticMXBean.class to a different location. Refer the copied jar in build path using "Add External jar". This allows you to create Object and get the Heap dump.