It seems as though jenkins somehow gets in a situation where at the end of running a job, at the point of trying to publish nunit results it throws an NPE, of the form:

ERROR: Publisher hudson.plugins.nunit.NUnitPublisher aborted due to exception
java.lang.NullPointerException
at hudson.model.Run.getRootDir(Run.java:927)
at hudson.tasks.junit.TestResultAction.getDataFile(TestResultAction.java:91)
at hudson.tasks.junit.TestResultAction.load(TestResultAction.java:147)
at hudson.tasks.junit.TestResultAction.getResult(TestResultAction.java:97)
at hudson.tasks.junit.TestResultAction.getResult(TestResultAction.java:55)
at hudson.tasks.test.AbstractTestResultAction.findCorrespondingResult(AbstractTestResultAction.java:183)
at hudson.tasks.test.TestResult.getPreviousResult(TestResult.java:145)
at hudson.tasks.junit.SuiteResult.getPreviousResult(SuiteResult.java:296)
at hudson.tasks.junit.CaseResult.getPreviousResult(CaseResult.java:375)
at hudson.tasks.junit.CaseResult.freeze(CaseResult.java:486)
at hudson.tasks.junit.SuiteResult.freeze(SuiteResult.java:338)
at hudson.tasks.junit.TestResult.freeze(TestResult.java:564)
at hudson.tasks.junit.TestResultAction.setResult(TestResultAction.java:74)
at hudson.tasks.junit.TestResultAction.<init>(TestResultAction.java:67)
at hudson.plugins.nunit.NUnitPublisher.recordTestResult(NUnitPublisher.java:150)
at hudson.plugins.nunit.NUnitPublisher.perform(NUnitPublisher.java:109)
at hudson.tasks.BuildStepMonitor$3.perform(BuildStepMonitor.java:36)
at hudson.model.AbstractBuild$AbstractBuildExecution.perform(AbstractBuild.java:810)
at hudson.model.AbstractBuild$AbstractBuildExecution.performAllBuildSteps(AbstractBuild.java:785)
at hudson.model.Build$BuildExecution.post2(Build.java:183)
at hudson.model.AbstractBuild$AbstractBuildExecution.post(AbstractBuild.java:732)
at hudson.model.Run.execute(Run.java:1568)
at hudson.model.FreeStyleBuild.run(FreeStyleBuild.java:46)
at hudson.model.ResourceController.execute(ResourceController.java:88)
at hudson.model.Executor.run(Executor.java:236)

Once this starts happening it continues to happen for every build for that particular job. A restart does not stop this behaviour from happening. We noted a while back that deleting the build history from the filesystem for this job does allow it carry on successfully, until such time as the error appears again.

Very recently a team member noted that the number of builds in the history for that job was equal to (or thereabouts [most recent #405 oldest #306) to the value stored in the configuration setting 'Max # of builds to keep' (in our case 100). This could be a co-incidence, and I've upped the setting to 200 to see if builds start working again (but this takes ~6 hours to reach the failing job), but it does look like a smoking gun

I had hoped that it would be related to https://issues.jenkins-ci.org/browse/JENKINS-16194 but having upgraded to the latest version we still see this issue.

I'm mostly logging this in case others are seeing it