I've managed to break Jenkins while trying to fix some other problems. Now whenever I run a job it immediately fails with the following error:

java.lang.NullPointerException
at java.util.TreeMap.putAll(TreeMap.java:313)
at hudson.slaves.EnvironmentVariablesNodeProperty.buildEnvVars(EnvironmentVariablesNodeProperty.java:85)
at hudson.model.Computer.buildEnvironment(Computer.java:1195)
at hudson.model.Job.getEnvironment(Job.java:385)
at hudson.model.Run.getEnvironment(Run.java:2419)
at org.jenkinsci.plugins.workflow.job.WorkflowRun.getEnvironment(WorkflowRun.java:500)
at org.jenkinsci.plugins.workflow.cps.CpsScmFlowDefinition.create(CpsScmFlowDefinition.java:112)
at org.jenkinsci.plugins.workflow.cps.CpsScmFlowDefinition.create(CpsScmFlowDefinition.java:68)
at org.jenkinsci.plugins.workflow.job.WorkflowRun.run(WorkflowRun.java:310)
at hudson.model.ResourceController.execute(ResourceController.java:99)
at hudson.model.Executor.run(Executor.java:432)
Finished: FAILURE

I found this answer

However, I am still able to access the jobs using a direct url to them. This folder had a view added to it using the build-monitor-plugin and I suspected it messed up something after the restart. So I uninstalled the plugin but that did not fix the view. I have also manually removed all files related to this plugin but that also does not help. When I visit the folder I see following error in the log:

2022-01-06 05:29:47.232 0000 [id=87]    WARNING h.i.i.InstallUncaughtExceptionHandler#handleException: Caught unhandled exception with ID cb5bdf8c-2a97-4360-8f80-95df2c5c719b
org.apache.commons.jelly.JellyTagException: jar:file:/app/jenkins/war/WEB-INF/lib/jenkins-core-2.319.1.jar!/hudson/model/View/index.jelly:42:43: <st:include> org.apache.commons.jelly.JellyTagException: jar:file:/app/jenkins/war/WEB-INF/lib/jenkins-core-2.319.1.jar!/lib/hudson/projectView.jelly:67:24: <d:invokeBody> `java.lang.NullPointerException
    at org.apache.commons.jelly.impl.TagScript.handleException(TagScript.java:726)
    at org.apache.commons.jelly.impl.TagScript.run(TagScript.java:281)
    at org.apache.commons.jelly.impl.ScriptBlock.run(ScriptBlock.java:95)`

CodePudding user response：

Finally managed to fix both issues.

What happened? Sequence of installing the plugin-in build-monitor-plugin, restarting Jenkins and then uninstalling the plug-in left some of the files in Jenkins in a corrupted state. A state from which Jenkins version 2.263.3 was unable to recover even though it kept on recreating the files but every time it was creating the same corrupted files again.

Corrupted Files There were two files that got corrupted and both are named config.xml. First one is in the top most level directory of Jenkins. It is supposed to be as follows in case you have environment variables:

  <globalNodeProperties>
    <hudson.slaves.EnvironmentVariablesNodeProperty>
      <envVars serialization="custom">
        <unserializable-parents/>
        <tree-map>
          <default>
            <comparator />
          </default>
          <int>2</int> <!-- This number indicates how many key/value pairs will follow it -->
          <string></string>
          <string></string>
          ...
        </tree-map>
      </envVars>
    </hudson.slaves.EnvironmentVariablesNodeProperty>
  </globalNodeProperties>

Something similar was also suggested in Jenkins - Problem: hudson.model.Queue$MaintainTask failed but the value of <comparator> class mentioned there did not work. I figured out the correct value by installing a separate instance of Jenkins and comparing the new config.xml with the old one.

Similarly the other config.xml that was broken was for the folder which was not showing up properly as can be seen in question. For that I created another folder and compared it's config.xml with the broken one and found following two lines missing from the <folderViews>:

  ...
  <folderViews>
    ...
    <primaryView>All</primaryView>
    <tabBar />
  </folderViews>
  ...

Adding these two lines resolved the issue.