OutOfMemoryError with Java

Recently had to investigate an OutOfMemoryError issue possibly caused by my Java code.  Some tools/information I have found useful so far are:

1. VisualVM - profiler that you probably already have installed.  Check for <JAVA_HOME>/bin/jvisualvm.exe
   
• If you have problems installing plugins that you need, for example, as above, download and install manually  
• If you encounter a "Cannot connect to service" error, consider attempting with JConsole first by running <JAVA_HOME>/bin/jconsole -debug to determine the reason why;  Troubleshooting connection problems in JConsole
2. Generations - describes Java memory management.  It will help you interpret the graphs in the Visual GC plugin
3. Understanding Weak References - never heard of weak references in the context of Java?  Me too

Hudson having problem with Subversion: hudson.model.Job.hasCascadingProject()Z

One day, a few of our Hudson jobs (but not all) started to have this error when executing.

FATAL: hudson.model.Job.hasCascadingProject()Z
java.lang.NoSuchMethodError: hudson.model.Job.hasCascadingProject()Z
 at hudson.scm.PerJobCredentialStore.getXmlFile(PerJobCredentialStore.java:137)
 at hudson.scm.PerJobCredentialStore.<init>(PerJobCredentialStore.java:58)
 at hudson.scm.SubversionSCM$DescriptorImpl.createAuthenticationProvider(SubversionSCM.java:1820)
 at hudson.scm.SubversionSCM$DescriptorImpl.getRepository(SubversionSCM.java:2069)
 at hudson.scm.SubversionSCM$DescriptorImpl.checkRepositoryPath(SubversionSCM.java:2039)
 at hudson.scm.SubversionSCM.repositoryLocationsNoLongerExist(SubversionSCM.java:2272)
 at hudson.scm.SubversionSCM.checkout(SubversionSCM.java:748)
 at hudson.scm.SubversionSCM.checkout(SubversionSCM.java:711)
 at hudson.model.AbstractProject.checkout(AbstractProject.java:1229)
 at hudson.model.AbstractBuild$AbstractRunner.checkout(AbstractBuild.java:507)
 at hudson.model.AbstractBuild$AbstractRunner.run(AbstractBuild.java:424)
 at hudson.model.Run.run(Run.java:1367)
 at hudson.model.FreeStyleBuild.run(FreeStyleBuild.java:46)
 at hudson.model.ResourceController.execute(ResourceController.java:88)
 at hudson.model.Executor.run(Executor.java:145)

This turns out to be at the Subversion check-out step:

You can click on "Update credentials" to go to a screen to enter in your credentials.  But you might get the following error:

HTTP ERROR 500

Problem accessing /hudson/job/PWS-OCDT/descriptorByName/hudson.scm.SubversionSCM/postCredential. Reason:

    hudson.model.Job.hasCascadingProject()Z

Caused by:

java.lang.NoSuchMethodError: hudson.model.Job.hasCascadingProject()Z
 at hudson.scm.PerJobCredentialStore.getXmlFile(PerJobCredentialStore.java:137)

At this point, check the file-system of your Hudson server.  Under <HUDSON_HOME>\jobs\<Job name> you may notice that compared to Jobs that are working, the problematic job does not have a "subversion.credentials" file.  Copy over this file as-is to the directory.  No Hudson re-start is necessary; just go back to the Dashboard and choose the problematic Job.  From this point, you should be able to choose "Update credentials" and work through the screens without getting an unhelpful

hudson.model.Job.hasCascadingProject()Z 

error.  FYI, this is Hudson ver. 2.1.2 and our Subversion server location changed, which may have caused this issue.