sshagent seems to cause serialization failure

[David Karr]

In a Jenkinsfile, I'm trying to scp a zip file to a remote host, and ssh some commands to unpack it when it gets there.

I managed to add a "SSH username with private key" credential, and I can see it in the "Credentials" list.  I'm referencing that uuid in my "sshagent" block.

When I run the job, I see the following:

JP_MechIdPrivateKey[<myusername>-private-key] class[java.lang.String]

[ssh-agent] Using credentials <myusername>
[ssh-agent] Looking for ssh-agent implementation...
[ssh-agent]   Java/JNR ssh-agent
[ssh-agent] Skipped registering BouncyCastle, not running on a remote agent
[ssh-agent] Started.
[Pipeline] {

[Pipeline] sh
[ssh-agent] Stopped.
[usl-parent] Running shell script
[Pipeline] }
[Pipeline] // sshagent
[Pipeline] }
[Pipeline] // dir
[Pipeline] sh
...
java.io.NotSerializableException: sun.nio.fs.UnixPath
    at org.jboss.marshalling.river.RiverMarshaller.doWriteObject(RiverMarshaller.java:860)
    at org.jboss.marshalling.river.BlockMarshaller.doWriteObject(BlockMarshaller.java:65)
...
Caused by: an exception which occurred:
    in field locals
    in field caller
    in field e
    in field program
    in field thread
    in field body
    in field step
    in field thread
    in field this$0
    in field returnAddress
    in field parent
    in field caller
    in field parent
    in field parent
    in field parent
    in field parent
    in field capture
    in field def
    in field closures
    in object org.jenkinsci.plugins.workflow.cps.CpsThreadGroup@d12af23
Finished: FAILURE

The code in question looks like this:

                    println "JP_MechIdPrivateKey[${JP_MechIdPrivateKey}] class[${JP_MechIdPrivateKey.class.name}]"
                    sshagent (credentials: [JP_MechIdPrivateKey]) {
                        sh "scp ${javadocJarPath} ${JP_JavadocJarHost}:/tmp"
                        sh "ssh ${JP_JavadocJarHost} \"cd ${JP_JavadocRootRemotePath}; rm -rf ${versionNumber}; mkdir ${versionNumber}\""
                        sh "ssh ${JP_JavadocJarHost} \"cd ${JP_JavadocRootRemotePath}; jar xvf /tmp/${baseFileName}\""
                    }

I believe I've heard that in order to avoid serialization issues, I have to put things in @NonCPS methods, but I don't understand what parts of this would need to go into a @NonCPS method, and what CANNOT go into a @NonCPS method.

[David Karr]

Oh, and I tried running this with the "sshagent" block commented out, and the exception does not occur (and nothing useful gets done, of course), so it's definitely coming from that, even though the stacktrace doesn't give me any hint of where it's happening in the script.