How to Dynamically Create Jenkins Agent Nodes Using Groovy

The article explains a method to dynamically create Jenkins agent nodes for elastic builds, using native Groovy code instead of the Kubernetes plugin.

Import Packages

import hudson.model.Node.Mode
import hudson.slaves.*
import jenkins.model.Jenkins

Add a New Node

String agentName = "zeyang"
String executorNum = "1"
String agentLabel = "JenkinsPod"

agent_node = new DumbSlave(agentName, "Jenkins pod", "/opt/jenkins", executorNum,
               Mode.EXCLUSIVE,
               agentLabel,
               new JNLPLauncher(),
               RetentionStrategy.INSTANCE)
Jenkins.instance.addNode(agent_node)

The parameters are:

agentName : node name

executorNum : number of executors (as a string)

agentLabel : node label

description : description text

JNLPLauncher() : launch method

Mode.EXCLUSIVE : restrict job scheduling to this node

RetentionStrategy.INSTANCE : keep the node always online

Retrieve Node Information

node = Jenkins.instance.getNode(agentName)
computer = node.computer
jenkinsUrl = Jenkins.instance.rootUrl.trim().replaceAll('/$', '')

return ""{
"jenkinsUrl" : "${jenkinsUrl}",
"jenkinsHome": "${node.remoteFS.trim()}",
"computerUrl": "${computer.url.trim().replaceAll('/$', '') as String}",
"computerSecret": "${computer.jnlpMac.trim()}"
}""

This script fetches the newly created node's configuration and returns it as a JSON string for downstream processing.

By completing these steps, the first phase of elastic build automation is achieved, and the retrieved node data can later be used to replace pod templates and launch containers in a Kubernetes cluster.