Hosting Jenkins on a Kubernetes cluster is beneficial for Kubernetes-based DevOps and dynamic container-based scalable Jenkins agents.
what is Jenkins in DevOps?
An open-source automation server that enables developers around the world to reliably build, test, and deploy their software. Jenkins can be used as a simple CI server or turned into the continuous delivery hub for any project.According to the official site
Why Choose Jenkins for your DevOps?
Continuous Integration and Continuous Delivery
As an extensible automation server, Jenkins can be used as a simple CI server or turned into the continuous delivery hub for any project.
Jenkins is a self-contained Java-based program, ready to run out-of-the-box, with packages for Windows, Linux, macOS and other Unix-like operating systems.
Jenkins can be easily set up and configured via its web interface, which includes on-the-fly error checks and built-in help.
Jenkins can be extended via its plugin architecture, providing nearly infinite possibilities for what Jenkins can do.
Jenkins can easily distribute work across multiple machines, helping drive builds, tests and deployments across multiple platforms faster.
With hundreds of plugins in the Update Center, Jenkins integrates with practically every tool in the continuous integration and continuous delivery toolchain.
Kubernetes Jenkins Deployment.
Lets get started with deploying Jenkins on Kubernetes.
Create a Namespace
Create a Namespace for Jenkins. It is good to categorize all the devops tools as a separate namespace from other applications.
kubectl create namespace devops-tools
Create a service account with Kubernetes admin permissions.
serviceAccount.yaml file and copy the following admin service account manifest.
--- apiVersion: rbac.authorization.k8s.io/v1 kind: ClusterRole metadata: name: jenkins-admin rules: - apiGroups: [""] resources: ["*"] verbs: ["*"] --- apiVersion: v1 kind: ServiceAccount metadata: name: jenkins-admin namespace: devops-tools --- apiVersion: rbac.authorization.k8s.io/v1 kind: ClusterRoleBinding metadata: name: jenkins-admin roleRef: apiGroup: rbac.authorization.k8s.io kind: ClusterRole name: jenkins-admin subjects: - kind: ServiceAccount name: jenkins-admin namespace: devops-tools
serviceAccount.yaml creates a
jenkins-admin ServiceAccount and binds the clusterRole to the service account.
jenkins-admin cluster role has all the permissions to manage the cluster components. You can also restrict access by specifying individual resource actions.
Now create the service account using kubectl.
volume.yaml and copy the following persistent volume manifest.
kind: StorageClass apiVersion: storage.k8s.io/v1 metadata: name: local-storage provisioner: kubernetes.io/no-provisioner volumeBindingMode: WaitForFirstConsumer --- apiVersion: v1 kind: PersistentVolume metadata: name: jenkins-pv-volume labels: type: local spec: storageClassName: local-storage claimRef: name: jenkins-pv-claim namespace: devops-tools capacity: storage: 10Gi accessModes: - ReadWriteOnce local: path: /mnt nodeAffinity: required: nodeSelectorTerms: - matchExpressions: - key: kubernetes.io/hostname operator: In values: - worker-node01 --- apiVersion: v1 kind: PersistentVolumeClaim metadata: name: jenkins-pv-claim namespace: devops-tools spec: storageClassName: local-storage accessModes: - ReadWriteOnce resources: requests: storage: 3Gi
You can get the worker node hostname using the kubectl.
kubectl get nodes
Create local persistent volume for persistent Jenkins data on Pod restarts.
To create the volume using kubectl
kubectl create -f volume.yaml
Create a deployment YAML and deploy it.
Create a Deployment file named
deployment.yaml and copy the following deployment manifest.
Here we are using the latest Jenkins LTS docker image from the Docker hub.
apiVersion: apps/v1 kind: Deployment metadata: name: jenkins namespace: devops-tools spec: replicas: 1 selector: matchLabels: app: jenkins-server template: metadata: labels: app: jenkins-server spec: securityContext: fsGroup: 1000 runAsUser: 1000 serviceAccountName: jenkins-admin containers: - name: jenkins image: jenkins/jenkins:lts resources: limits: memory: "2Gi" cpu: "1000m" requests: memory: "500Mi" cpu: "500m" ports: - name: httpport containerPort: 8080 - name: jnlpport containerPort: 50000 livenessProbe: httpGet: path: "/login" port: 8080 initialDelaySeconds: 90 periodSeconds: 10 timeoutSeconds: 5 failureThreshold: 5 readinessProbe: httpGet: path: "/login" port: 8080 initialDelaySeconds: 60 periodSeconds: 10 timeoutSeconds: 5 failureThreshold: 3 volumeMounts: - name: jenkins-data mountPath: /var/jenkins_home volumes: - name: jenkins-data persistentVolumeClaim: claimName: jenkins-pv-claim
In this Jenkins Kubernetes deployment we have used the following.
securityContextfor Jenkins pod to be able to write to the local persistent volume.
- Liveliness and readiness probe.
- Local persistent volume based on local storage class that holds the Jenkins data path
Create a service YAML and deploy it.
service.yaml and copy the following service manifest.
apiVersion: v1 kind: Service metadata: name: jenkins-service namespace: devops-tools annotations: prometheus.io/scrape: 'true' prometheus.io/path: / prometheus.io/port: '8080' spec: selector: app: jenkins-server type: NodePort ports: - port: 8080 targetPort: 8080 nodePort: 32000
We have created a deployment. However, it is not accessible to the outside world. For accessing the Jenkins deployment from the outside world, we should create a service and map it to the deployment.
Note: Here, we are using the type as
NodePortwhich will expose Jenkins on all kubernetes node IPs on port 32000. If you have an ingress setup, you can create an ingress rule to access Jenkins. Also, you can expose the Jenkins service as a Loadbalancer if you are running the cluster on AWS, Google, or Azure cloud.
Create the Jenkins service using kubectl.
kubectl apply -f service.yaml
Access the Jenkins application on a Node Port.
Now if you browse to any one of the Node IPs on port
32000, you will be able to access the Jenkins dashboard.
Jenkins will ask for the initial Admin password when you access the dashbaord for the first time.
You can get that from the pod logs either from the kubernetes dashboard or CLI. You can get the pod details using the following CLI command.
kubectl get pods --namespace=devops-tools
And with the pod name, you can get the logs as shown below. replace the pod name with your pod name.
kubectl logs jenkins-deployment-2539456353-j00w5 --namespace=jenkins
Alternatively, you can run the exec command to get the password directly from the location as show below.
kubectl exec -it jenkins-559d8cd85c-cfcgk cat /var/jenkins_home/secrets/initialAdminPassword -n devops-tools
Once you enter the password you can proceed installing the suggested plugin and creating a admin user. All these steps are self-explanatory from the Jenkins dashboard.
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