jenkins critical error after plugin update - jenkins

Question

I attempted to update a couple of my jenkins plugins (don't remember which) but got hung. After about 15 mins, I decided to restart the jenkins server. This is what I get on the jenkins UI:
org.jvnet.hudson.reactor.ReactorException: java.lang.Error: java.lang.reflect.InvocationTargetException
at org.jvnet.hudson.reactor.Reactor.execute(Reactor.java:246)
at jenkins.InitReactorRunner.run(InitReactorRunner.java:43)
at jenkins.model.Jenkins.executeReactor(Jenkins.java:894)
at jenkins.model.Jenkins.<init>(Jenkins.java:796)
at hudson.model.Hudson.<init>(Hudson.java:81)
at hudson.model.Hudson.<init>(Hudson.java:77)
at hudson.WebAppMain$2.run(WebAppMain.java:214)
Caused by: java.lang.Error: java.lang.reflect.InvocationTargetException
at hudson.init.InitializerFinder.invoke(InitializerFinder.java:124)
at hudson.init.InitializerFinder$TaskImpl.run(InitializerFinder.java:184)
at org.jvnet.hudson.reactor.Reactor.runTask(Reactor.java:259)
at jenkins.model.Jenkins$7.runTask(Jenkins.java:883)
at org.jvnet.hudson.reactor.Reactor$2.run(Reactor.java:187)
at org.jvnet.hudson.reactor.Reactor$Node.run(Reactor.java:94)
at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:886)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:908)
at java.lang.Thread.run(Thread.java:662)
Caused by: java.lang.reflect.InvocationTargetException
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:597)
at hudson.init.InitializerFinder.invoke(InitializerFinder.java:120)
... 8 more
Caused by: java.lang.NoClassDefFoundError: hudson/PluginManager$PluginUpdateMonitor
at hudson.maven.PluginImpl.init(PluginImpl.java:54)
... 13 more
Caused by: java.lang.ClassNotFoundException: hudson.PluginManager$PluginUpdateMonitor
at java.net.URLClassLoader$1.run(URLClassLoader.java:202)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader.findClass(URLClassLoader.java:190)
at java.lang.ClassLoader.loadClass(ClassLoader.java:306)
at java.lang.ClassLoader.loadClass(ClassLoader.java:247)
... 14 more
I attempted to update the war from 1.486 to 1.502 but no change in behavior. What can I do to get Jenkins operational again?

Answer 1

It's a known bug.
Copy/pasted for reference:
Start 1.490 on a clean home dir, then ask to upgrade the Maven plugin to version 1.491, and restart. After the restart, there are linkage errors from the Maven plugin, predictably enough (since it is using 1.491+ core APIs); but all of Jenkins fails to start, making it impossible to use the GUI to back out the update. (Workaround: delete $JENKINS_HOME/plugins/maven-plugin.jpi.pinned.)

Answer 2

Didn't work for me, so I just deleted every $JENKINS_HOME/plugins/maven-plugin* file.
Done.

Answer 3

I got the Same Error When Trying to Update the Plugins & Delete \Unpin some Plugins at the Same time.
Finally was able to Solve the issue by, Deleting all the "DISABLED" files in Plugins folder, restored back all the Maven files (if deleted on suggestion by previous Solutions), restarted the Jenkins Instance.
Understood this is because of Conflict with Plugins loading.

Answer 4

None of the above mentioned method is working for me.
Workaround: delete $JENKINS_HOME/plugins/maven-plugin.jpi.pinned
Deleting all the "DISABLED" files in Plugins folder, restored back all the Maven files
As per https://issues.jenkins-ci.org/browse/JENKINS-43446 :
I downgraded my maven to version 3.3.9 and It worked for me.