Using HeapDumpOnOutOfMemoryError parameter for heap dump for JBoss

I was told I can add the -XX:+HeapDumpOnOutOfMemoryError parameter to my JVM start up options to my JBoss start up script to get a heap dump when we get an out of memory error in our application. I was wondering where this data gets dumped? Is it just to the console, or to some log file? If it's just to the console, what if I'm not logged into the Unix server through the console?

5 Answers

Here's what Oracle's documentation has to say:

By default the heap dump is created in a file called java_pid.hprof in the working directory of the VM, as in the example above. You can specify an alternative file name or directory with the -XX:HeapDumpPath= option. For example -XX:HeapDumpPath=/disk2/dumps will cause the heap dump to be generated in the /disk2/dumps directory.

You can view this dump from the UNIX console.

The path for the heap dump will be provided as a variable right after where you have placed the mentioned variable.

E.g.:

-XX:+HeapDumpOnOutOfMemoryError -XX:HeapDumpPath=${DOMAIN_HOME}/logs/mps" 

You can view the dump from the console on the mentioned path.

I found it hard to decipher what is meant by "working directory of the VM". In my example, I was using the Java Service Wrapper program to execute a jar - the dump files were created in the directory where I had placed the wrapper program, e.g. c:\myapp\bin. The reason I discovered this is because the files can be quite large and they filled up the hard drive before I discovered their location.

If you are not using "-XX:HeapDumpPath" option then in case of JBoss EAP/As by default the heap dump file will be generated in "JBOSS_HOME/bin" directory.

If you only configure -XX:+HeapDumpOnOutOfMemoryError parameter then heapdump will be generated in JBOSS_HOME/bin directory for OpenJDK/Oracle JDK. If you are using IBM JDK then heapdump will be created under /tmp directory as phd file. -XX:HeapDumpPath option gives us more feasibility for configuring our custom headpump path location (-XX:HeapDumpPath=/my-custom-jboss-server-path/). It's recommended to have this parameters configured in your environment as it will collect heapdump on OutOfMemory error for analyzing the issue with memory leak of the application or checking any large object retention in the application.