Make jenkins agent more flexible

[Vlatombe]

• The name of the agent container can now be customized (the jnlp deprecated name is no longer required)
• It is no longer required to extend the jenkins inbound-agent image anymore, or provide the agent.jar in the image. Custom images only need to provide a JRE, and required build tools.

One example of usage

podTemplate(agentContainer:'foo',
            agentInjection: true,
            yaml:'''
spec:
  containers:
  - name: foo
    image: eclipse-temurin:22.0.2_9-jre
''') {
  node(POD_LABEL) {
    sh 'true'
  }
}

Testing done

Submitter checklist

• Make sure you are opening from a topic/feature/bugfix branch (right side) and not your main branch!
• Ensure that the pull request title represents the desired changelog entry
• Please describe what you did
• Link to relevant issues in GitHub or Jira
• Link to relevant pull requests, esp. upstream and downstream changes
• Ensure you have provided tests - that demonstrates feature works or fixes the issue

[jglick]

Looks promising! Now we just need to find a statically-linked JRE we can copy in as well…

[Vlatombe]

we just need to find a statically-linked JRE we can copy in as well…

Not sure it exists yet
https://bugs.openjdk.org/browse/JDK-8303796

[jglick]

I feel like the change in this case is more confusing than helpful? It destroys the parallelism between the containers.

[Vlatombe]

What parallelism ? You still have a maven and a golang container, the only difference is that the jnlp container is gone.

[jglick]

Right but you are using both of these containers for similar purposes—running selected build steps—yet one is being used as the agent container merely because its toolchain happens to include a JRE.

[Vlatombe]

Yes, as long as you have a JRE in the toolchain and you can avoid container step (and associated scalability issues), I think it is good.

[jglick]

https://github.com/jenkinsci/kubernetes-plugin/blob/master/README.md#multiple-containers-support should be updated too?

[Vlatombe]

master/README.md#multiple-containers-support should be updated too?

Done

[balakine]

I don't think this should be called done https://github.com/jenkinsci/kubernetes-plugin/blob/master/README.md

Within these pods, there is always one special container jnlp that is running the Jenkins agent.

Not true

Commands will be executed by default in the jnlp container

Not true

Multiple containers can be defined in a pod. One of them is automatically created with name jnlp, ...

Not true

If you want to provide your own Docker image for the inbound agent, you must name the container jnlp so it overrides the default one.

Not true

[Vlatombe]

@balakine Feel free to provide a pull request to fix these

[balakine]

If only the author of the change that rendered the documentation obsolete was still in the room...

[Vlatombe]

I'm sorry, but your comment, even if true, was rude. If you are unsatisfied, please help yourself.

[balakine]

I apologize for hurting your feelings. You are spending your personal time for a project I benefit from, so I should be choosing kinder words and comment in a more constructive manner.