Exception occurs on websphere liberty server server start in eclipse

Question

I am running an application using WLP and when I start my server in eclipse, I get exceptions like below:

Exception: java.lang.OutOfMemoryError thrown from the UncaughtExceptionHandler in thread "Shared TCPChannel NonBlocking Accept Thread"

Exception: java.lang.OutOfMemoryError thrown from the UncaughtExceptionHandler in thread "Default Executor-thread-34"

Exception: java.lang.OutOfMemoryError thrown from the UncaughtExceptionHandler in thread "kernel-command-listener"

I was able to start the server and host the application earlier. And this just started happening now. Also, I can start my other wlp servers for different applications.

Any pointers will be appreciated!

Thanks

Answer 1

Often the OOM error itself will provide a clue. If you look in the logs to see the stack trace of the exception, the message may indicate what resource could not be allocated. OOMs can be thrown by running out of Java heap space, native space, or system resources - like threads, etc.

There are a lot of good resources for diagnosing OOMs, like: https://docs.oracle.com/javase/8/docs/technotes/guides/troubleshoot/memleaks002.html

If nothing changed (like you didn't change the heap settings in the server's jvm.options file, or add a big new feature or app to the server), then more than likely the problem is from the box itself. You may have exceeded the max threads setting for your operating system or exceeded the system's memory (physical + swap), file handles, etc.

If that is the case, you should check to see what your operating system's capabilities are (i.e. "ulimit -a" for unix-based systems) and check what is currently running ("top", "vmstat", etc.). You may be able to tweak your ulimit settings (assuming you are running on Mac/Linux/etc. - I believe Windows has similar settings, but I don't know them offhand) to allow this server and all other processes to run simultaneously, but more likely you will need to stop running some processes.

Hope this helps, Andy