Grails restart loop

The Problem

The other day I was doing some bulk file operations on a grails project. I was moving some classes in bulk from a plug-in into an application. After I made the move I ran into a puzzling issue: grails kept restarting in a loop. Each time the plugin scanner ran (every 5 seconds after startup), grails would complain that it needed to compile 1 file. This went on for a few minutes until my app ran out of PermGen and crashed. To make matters worse, grails would not tell me which file it was recompiling even with logging set to trace!

This seems to be a classic grails issue that is rare, but frustrating.

The Cause

The likely cause is a groovy file outside the correct package or with a file name that does not match the case name. The latter can happen when tinkering around between case sensitive and case insensitive file systems as is common when developing with OS X.

The Fix

To fix it you need to find the messed up class and fix it. The below method is crude, but works.

1. If your app crashes quickly due to PermGen issues, provide more PermGen space. You’ll need at least 2 or 3 minutes of run time for this to work. Use the JVM argument -XX:MaxPermSize=1024m if you have to.
2. Let your app run for a few minutes. Let it recompile that file a few times.
3. If your app has not already crashed, stop it
4. Now to find the compiled class file. Go to the directory where grails claims to be compiling the file. In my case it was in ~/.grails/1.2.0/projects/fooApp/classes
5. Run this shell command to see when most of the files were updated: find ./ | xargs ls -al The vast majority of the listed files should all have an updated time within the same minute. In my case it was 15:17 Lets fileter those out and see what’s left behind.
6. Run another find command and see the newer files: find ./ | xargs ls -al | grep -v 15:17. I saw a few files and headers that had to be ignored, but in the middle I found the class name which was compiled from a .groovy file of a different name.
7. Go back to your app code and resolve the conflicted state of your groovy file(s)
8. Quit cursing under your breath and go have a beer if you need one