Jenkins Master Slave on K8s

Introduction

Jenkins Master-Slave architecture has been designed for distributed builds. So, the workload will be distributed to slaves and master act as a managing and scheduling node. Here we’ll discuss implementing Jenkins Master-Slave setup on K8s.

Prerequisites

• An up and running K8s cluster.
• Running and accessible Jenkins service on K8s cluster.
• Jenkins should have Kubernetes plugin installed.

How ToDo

• Navigate to Jenkins -> Configure System and configure your K8s cluster as shown below in Kubernetes plugin. Here I have deployed Jenkins in jenkins namespace.
• Click on Test Connection and confirm cluster is accessible to Jenkins.

• Scroll down to Kubernetes Pod Template and configure it with jnlp pod template as shown below.

• jnlp.yml

apiVersion: v1
kind: Pod
metadata:
  labels:
    app: jnlp
  name: jnlp
spec:
  containers:
  - image: jenkins/jnlp-slave:3.27-1-alpine
    imagePullPolicy: IfNotPresent
    name: jnlp
    resources: {}
  dnsPolicy: ClusterFirst
  restartPolicy: Never
status: {}

• Finally, click on Save and navigate to Jenkins Home page
• Create a Pipeline job.
  New Item -> Enter an item name -> Pipeline -> OK
• Fill Pipeline script box in Pipeline section with below script.

pipeline {
    agent {
        kubernetes {
            cloud "kubernetes" // Cloud Kubernetes Name
            label "jnlp"       // jnlp pod template label
        }
    }
    stages {
        stage("Print Env") {
            steps {
                container("jnlp")  {
                    sh "printenv"
                    sh "sleep 60"
                }
            }
        }
    }
}

• Run the job and monitor the Kubernetes. You could see jnlp slave running pods. Meanwhile Jenkins UI as well.

$ kubectl get po -n jenkins
NAME                     READY     STATUS    RESTARTS   AGE
jenkins-85544876-p4mfz   1/1       Running   0          57m
jnlp-6cfdt               1/1       Running   0          11s

Writing feedback is Welcome.