How do I produce a heap dump with only a JRE?

Question

We have a JRE installed on our production environment, but not a JDK. The versions of the JRE and OS are below.

[me@mymachine ~]$ java -version
java version "1.6.0_45"
Java(TM) SE Runtime Environment (build 1.6.0_45-b06)
Java HotSpot(TM) 64-Bit Server VM (build 20.45-b01, mixed mode)
[me@mymachine ~]$ uname -a
Linux mymachine.mydomain.com 3.10.35-43.137.amzn1.x86_64 #1 SMP Wed Apr 2 09:36:59 UTC 2014 x86_64 x86_64 x86_64 GNU/Linux

It doesn’t appear as if the jmap tool is present anywhere on the system, and without root access, I’m not in a position to install it in any system location. What can I do to get a heap dump (i.e. produce a .hprof file)?

Also, we're using JBoss 7.1.3.AS if that matters.

Answer 1

Use jattach, a tool created by JVM hacker Andrei Pangin. It's tiny (24KB), works with just JRE and supports Linux containers.

jattach PID-OF-JAVA dumpheap <path to heap dump file>

Answer 2

Built-in tools like jmap, jconsole, and jvisualvm are only available in a JDK. Another option is to add the VM argument -XX:+HeapDumpOnOutOfMemoryError which tells the JVM to automatically generate a heap dump when an OutOfMemoryError occurs, and the argument -XX:HeapDumpPath to specify the path for the heap dump.

If you cannot upgrade your JRE to use tools like the ones in the server JRE 7 (http://www.oracle.com/technetwork/java/javase/downloads/server-jre7-downloads-1931105.html), you may have to consider third-party profiling tools like JProfiler or ones list here.