How can a Windows server be a slave to Jenkins running on Linux when there in an error installing the slave-agent.jnlp file?

Question

I want to have a Windows Server 2016 slave node with a master Jenkins (version 2.89.2) running on Red Hat Enterprise Linux 7.x. I am trying to install the slave-agent.jnlp file from the Jenkins web UI on the Windows server. I run this command for PowerShell opened as administrator:

javaws -verbose C:\Users\Administrator\Downloads\slave-agent.jnlp

I receive this error:

Error: The field <jnlp><application-desc><argument> has an invalid value:

Launch File

<jnlp codebase="http://FQDNofJenkinsServer:8080/computer/FQDNofWindowsSlave/" spec="1.0+"><information><title>Agent for FQDNofWindowsSlave</title><vendor>Jenkins project</vendor><homepage href="https://jenkins-ci.org/"/></information><security><all-permissions/></security><resources><j2se version="1.8+"/><jar href="http://FQDNofJenkinsServer:8080/jnlpJars/remoting.jar"/></resources><application-desc main-class="hudson.remoting.jnlp.Main"><argument>32ba31ca5f150c2b3491802b0b60e56574d970a9e601cebad656a113fe325a85</argument><argument>FQDNofWindowsSlave</argument><argument>-workDir</argument><argument/><argument>-internalDir</argument><argument/><argument>-url</argument><argument>http://FQDNofJenkinsServer:8080/</argument></application-desc></jnlp>


Exception

BadFieldException[ The field <jnlp><application-desc><argument> has an invalid value: ,]
    at com.sun.javaws.jnl.XMLFormat$10.visitElement(Unknown Source)
    at com.sun.javaws.jnl.XMLUtils.visitElements(Unknown Source)
    at com.sun.javaws.jnl.XMLFormat.buildApplicationDesc(Unknown Source)
    at com.sun.javaws.jnl.XMLFormat.process(Unknown Source)
    at com.sun.javaws.jnl.XMLFormat.parse(Unknown Source)
    at com.sun.javaws.jnl.LaunchDescFactory.buildDescriptor(Unknown Source)
    at com.sun.javaws.jnl.LaunchDescFactory.buildDescriptor(Unknown Source)
    at com.sun.javaws.Main.launchApp(Unknown Source)
    at com.sun.javaws.Main.continueInSecureThread(Unknown Source)
    at com.sun.javaws.Main.access$000(Unknown Source)
    at com.sun.javaws.Main$1.run(Unknown Source)
    at java.lang.Thread.run(Unknown Source)

I expect the command to work. I do not understand the error message. What should I do?

Answer 1

You have two arguments that are empty:

<application-desc main-class="hudson.remoting.jnlp.Main">
  <argument>32ba31ca5f150c2b3491802b0b60e56574d970a9e601cebad656a113fe325a85</argument>
  <argument>FQDNofWindowsSlave</argument>
  <argument>-workDir</argument>
  <argument/>
  <argument>-internalDir</argument>
  <argument/>
  <argument>-url</argument>
  <argument>http://FQDNofJenkinsServer:8080/</argument>
</application-desc>

Your error message has a comma in it:

BadFieldException[ The field has an invalid value: ,]

Other bad argument error messages on the internet have comma separated lists of bad arguments:

BadFieldException[ The field codebase has an invalid value: $$codebase,$$codebase]

So I'd guess those two empty arguments are the problem.

Answer 2

Jenkins provides agent.jar and a secret required to make a connection from the node to the master. Make sure the node is configured properly (Manage Jenkins → Manage Nodes → Node)

Ensure Java 1.8 is present on the Windows agent. Download the agent.jar file on the Windows machine, and run the command Jenkins provides, using Windows command prompt.

java -jar agent.jar -jnlpUrl http://localhost:8080/computer/example/slave-agent.jnlp -secret e6073ce49423ed54df4a24f918973f50dc760dd440013d3b30403c4a2c7501fd -workDir "c:\jenkins"