Building the CI/CD of the Future, create your first pipeline in Jenkins

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FAUN — Developer Community 🐾

6 min readJun 16, 2021

In this tutorial, I will share my experience as a DevOps engineer at Cloudify.co, this is the last post of the tutorial in which I will describe how to configure Jenkins Kubernetes plugin and how to create your first pipeline.

Building the CI/CD of the Future published posts:

Let’s start.

Kubernetes plugin for Jenkins

https://plugins.jenkins.io/kubernetes/
Jenkins plugin to run dynamic agents in a Kubernetes cluster.
Based on the Scaling Docker with Kubernetes article, automates the scaling of Jenkins agents running in Kubernetes.
The plugin creates a Kubernetes Pod for each agent started, defined by the Docker image to run, and stops it after each build.
Agents are launched using JNLP, so it is expected that the image connects automatically to the Jenkins controller. For that some environment variables are automatically injected:

Login to Jenkins

I explained how to get the password in the previous post:

https://faun.pub/building-the-ci-cd-of-the-future-install-and-configure-jenkins-c17feea00ef7

Get the admin password of Jenkins

printf $(kubectl get secret --namespace jenkins jenkins -o jsonpath="{.data.jenkins-admin-password}" | base64 --decode);echo

Configure Jenkins Kubernetes plugin

Go to dashboard -> Manage Jenkins -> Configure system

At the bottom of the page, you will see ‘Cloud’ section which is the configuration of the Jenkins Kubernetes plugin

Click on ‘a separate configuration page’

Let’s configure the most important fields:

Name: Kubernetes

Kubernetes URL: https://kubernetes.default

kubectl get svc -n default
NAME         TYPE        CLUSTER-IP   EXTERNAL-IP   PORT(S)   AGE
kubernetes   ClusterIP   10.100.0.1   <none>        443/TCP   1d

Kubernetes Namespace: jenkins (if you installed Jenkins to this namespace)

Credentials: click on Credentials -> add, select kind: ‘Kubernetes service account’

You created this service account in previous post, jenkins service account:
https://faun.pub/building-the-ci-cd-of-the-future-install-and-configure-jenkins-c17feea00ef7

Click ‘Test Connection’ to test connectivity with the k8s cluster, if you see some connectivity problem: validate you created service account properly.

Jenkins URL: http://jenkins.jenkins.svc.cluster.local:8080

Jenkins Tunnel: jenkins-agent.jenkins.svc.cluster.local:50000

kubectl get svc -n jenkins
NAME             TYPE        CLUSTER-IP       EXTERNAL-IP   PORT(S)    
jenkins          ClusterIP   10.100.208.3     <none>        8080/TCP    
jenkins-agent    ClusterIP   10.100.169.168   <none>      50000/TCP

Be careful with those two fields, validate you have a correct domain name for jenkins (jenkins.jenkins.svc.cluster.local), meaning jenkins service located in jenkins namespace with port 8080, also jenkins agent is correct, by running ‘kubectl get svc -n jenkins’.

If those fields misconfigured you will have multiple errors when running the pipeline, you can run ’kubectl logs/describe’ on the running pod and see the exact problem. In my case, I misconfigured Jenkins Tunnel and had multiple errors in JNLP agent which wasn’t able to connect to Jenkins through the tunnel because the service name I used for Jenkins Tunnel wasn’t correct.

You can use defaults for the rest.

Create a pipeline to test the integration of Jenkins with Kubernetes cluster

Click on Dashboard -> New Item

Let’s create a pipeline to test integration with Kubernetes by getting pods in all namespaces

We using ‘gcr.io/cloud-builders/kubectl’ docker container with kubectl tool and running ‘kubectl get pods -all-namespaces’, to check we have access to the cluster through the service account we configured.

podTemplate(label: 'mypod', containers: [
    containerTemplate(name: 'kubectl', image: 'gcr.io/cloud-builders/kubectl', command: 'cat', ttyEnabled: true)
  ]
  ) {
    node('mypod') {
        stage('Kubectl testing with k8s cluster') {
            container('kubectl') {
                sh("kubectl get pods --all-namespaces")
            }
        }
    }
}

Click to save, go to this pipeline and run build:

You can use nodeSelector if you use labels for worker nodes and want to run pipeline on specific worker nodes (I want to run pipeline on spot in this case):

podTemplate(label: 'mypod', nodeSelector: 'instance-type: spot', containers: [
    containerTemplate(name: 'kubectl', image: 'gcr.io/cloud-builders/kubectl', command: 'cat', ttyEnabled: true)
  ]
  ) {
    node('mypod') {
        stage('Kubectl testing with k8s cluster') {
            container('kubectl') {
                sh("kubectl get pods --all-namespaces")
            }
        }
    }
}

In the console output, you will see something similar to that


[Pipeline] Start of Pipeline
[Pipeline] podTemplate
[Pipeline] {
[Pipeline] node
Still waiting to schedule task
Created Pod: kubernetes jenkins/mypod-88fnc-fttdj
[Normal][jenkins/mypod-88fnc-fttdj][Scheduled] Successfully assigned jenkins/mypod-88fnc-fttdj to ip-192-168-36-50.eu-west-1.compute.internal
[Normal][jenkins/mypod-88fnc-fttdj][Pulled] Container image "gcr.io/cloud-builders/kubectl" already present on machine
[Normal][jenkins/mypod-88fnc-fttdj][Created] Created container kubectl
[Normal][jenkins/mypod-88fnc-fttdj][Started] Started container kubectl
[Normal][jenkins/mypod-88fnc-fttdj][Pulled] Container image "jenkins/inbound-agent:4.3-4" already present on machine
[Normal][jenkins/mypod-88fnc-fttdj][Created] Created container jnlp
[Normal][jenkins/mypod-88fnc-fttdj][Started] Started container jnlp
Agent mypod-88fnc-fttdj is provisioned from template mypod-88fnc
---
apiVersion: "v1"
kind: "Pod"
metadata:
  annotations:
    buildUrl: "http://jenkins.jenkins.svc.cluster.local:8080/job/Test%20k8s/2/"
    runUrl: "job/Test%20k8s/2/"
  labels:
    jenkins: "slave"
    jenkins/label-digest: "151e26c22cfdf1016d63f0cc3b4c6eeaf431ba3c"
    jenkins/label: "mypod"
  name: "mypod-88fnc-fttdj"
spec:
  containers:
  - command:
    - "cat"
    image: "gcr.io/cloud-builders/kubectl"
    imagePullPolicy: "IfNotPresent"
    name: "kubectl"
    resources:
      limits: {}
      requests: {}
    tty: true
    volumeMounts:
    - mountPath: "/home/jenkins/agent"
      name: "workspace-volume"
      readOnly: false
  - env:
    - name: "JENKINS_SECRET"
      value: "********"
    - name: "JENKINS_TUNNEL"
      value: "jenkins-agent.jenkins.svc.cluster.local:50000"
    - name: "JENKINS_AGENT_NAME"
      value: "mypod-88fnc-fttdj"
    - name: "JENKINS_NAME"
      value: "mypod-88fnc-fttdj"
    - name: "JENKINS_AGENT_WORKDIR"
      value: "/home/jenkins/agent"
    - name: "JENKINS_URL"
      value: "http://jenkins.jenkins.svc.cluster.local:8080/"
    image: "jenkins/inbound-agent:4.3-4"
    name: "jnlp"
    resources:
      limits: {}
      requests:
        memory: "256Mi"
        cpu: "100m"
    volumeMounts:
    - mountPath: "/home/jenkins/agent"
      name: "workspace-volume"
      readOnly: false
  restartPolicy: "Never"
  volumes:
  - emptyDir:
      medium: ""
    name: "workspace-volume"Running on mypod-88fnc-fttdj in /home/jenkins/agent/workspace/Test k8s
[Pipeline] {
[Pipeline] stage
[Pipeline] { (Kubectl testing with k8s cluster)
[Pipeline] container
[Pipeline] {
[Pipeline] sh+ kubectl get pods --all-namespacesNAMESPACE  NAME               READY   STATUS      RESTARTS   AGE
jenkins    mypod-88fnc-fttdj  2/2     Running     0          7s
...

In case you have some problems, troubleshoot your pod with ‘kubectl describe/logs’

kubectl describe pod mypod-88fnc-fttdj
kubectl logs pod mypod-88fnc-fttdj
kubectl logs pod mypod-88fnc-fttdj -c jnlp

Conclusion

It was the last post of the ‘Building the CI/CD of the Future’ series.

In this post, I covered how to configure Jenkins Kubernetes plugin and how to create your first pipeline to test connectivity with Kubernetes cluster from Jenkins by listing all the pods.

Thank you for reading, it was a great journey and I hope you enjoyed it.

If you want to be notified when the next post is published, please follow me here on medium and on Twitter (@warolv).

For consulting gigs, you can reach me on Upwork

Original story from my blog: https://igorzhivilo.com, I will save all configurations created in this tutorial in my Github (warolv).

References