Jenkins upgrade issue "Windows agents won't start" workaround

Today, when I tried to upgrade my team’s Jenkins server from Jenkins 2.235.1 to Jenkins 2.263.3, I met a problem that can not launch the Windows agent.

[2021-01-29 23:50:40] [windows-agents] Connecting to xxx.xxx.xxx.xxx

Checking if Java exists
java -version returned 11.0.2.
[2021-01-29 23:50:40] [windows-agents] Installing the Jenkins agent service
[2021-01-29 23:50:40] [windows-agents] Copying jenkins-agent.exe
ERROR: Unexpected error in launching an agent. This is probably a bug in Jenkins
Also: java.lang.Throwable: launched here
at hudson.slaves.SlaveComputer._connect(SlaveComputer.java:286)
at hudson.model.Computer.connect(Computer.java:435)
at hudson.slaves.SlaveComputer.doLaunchSlaveAgent(SlaveComputer.java:790)
...
...
at java.lang.Thread.run(Thread.java:748)
java.lang.NullPointerException
at hudson.os.windows.ManagedWindowsServiceLauncher.launch(ManagedWindowsServiceLauncher.java:298)

This issue had been raised in the Jenkins Jira project: JENKINS-63198 and JENKINS-63198

There is also a Windows Support Updates guide here that mentioned this problem.

Finally, I fixed this problem by the following steps:

Update windows-slaves-plugin to the lastest version 1.7 (fixes for Jenkins 2.248+)

Then the error should be like this

[2021-01-30 23:53:40] [windows-agents] Connecting to xxx.xxx.xxx.xxx
Checking if Java exists
java -version returned 11.0.2.
[2021-01-30 23:53:47] [windows-agents] Copying jenkins-agent.xml
[2021-01-30 23:53:48] [windows-agents] Copying agent.jar
[2021-01-30 23:53:48] [windows-agents] Starting the service
ERROR: Unexpected error in launching an agent. This is probably a bug in Jenkins
org.jinterop.dcom.common.JIException: Unknown Failure
	at org.jvnet.hudson.wmi.Win32Service$Implementation.start(Win32Service.java:149)
Caused: java.lang.reflect.InvocationTargetException
	at sun.reflect.GeneratedMethodAccessor219.invoke(Unknown Source)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.lang.reflect.Method.invoke(Method.java:498)
	at org.kohsuke.jinterop.JInteropInvocationHandler.invoke(JInteropInvocationHandler.java:140)
Also:   java.lang.Throwable: launched here

Then change jenkins-agent.exe.config file. remove or comment out this line <supportedRuntime version="v2.0.50727" /> as below

also do this for jenkins-slave.exe.config in case it also exists.

<configuration>
  <runtime>
    <!-- see http://support.microsoft.com/kb/936707 -->
    <generatePublisherEvidence enabled="false"/>
  </runtime>
  <startup>
    <!-- this can be hosted either on .NET 2.0 or 4.0 -->
    <!-- <supportedRuntime version="v2.0.50727" /> -->
    <supportedRuntime version="v4.0" />
  </startup>
</configuration>

Then try to Launch agent.

If it still does not work and has this error message “.NET Framework 2.0 or later is required on this computer to run a Jenkins agent as a Windows service”, you need to upgrade your .NET Framework.

Here is a link for update .NET Framework.

Hopefully, this could help you to fix connect the issue of the Windows agent. Let me know in case of any questions.

Author

Xianpeng Shen

Engineer. Builder. Maintainer.

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