Website deployment using Jenkins Cluster and Kubernetes

Content

• Configuration of Docker Host and Client
• Creation of Dockerfile for creation of Image to be used as an agent
• Configuration of Dynamic Cloud with Docker Agent in Jenkins
• Creation of Jenkins Slave Node Jobs

Prerequisites for the following setup includes:

• Setup of RHEL8 VM (in case base OS is Windows or MacOS)
• Setup of Docker, Jenkins and kubectl within the respective VM
• Minikube as well as kubectl needs to be installed in base OS

Configuration of Docker Host and Client

Consider two systems, one as Docker Host and the other as Docker Client, and understand the configuration required in both of them for implementing the following setup

Docker Host:

• To configure the Docker Host, the first thing that needs to be configured is /usr/lib/systemd/system/docker.service, this path could be obtained by the output of systemctl status docker.






“systemctl status docker” command output



• After accessing the docker.service file , the ExecStart keyword within it is modified as per requirement i.e., -H tcp:0.0.0.0:4243. This modification allows TCP communication from any IP on the port 4243. Port 4243 is also one of the Docker port used.






Modified docker.service file



• After the file is modified , it needs to be reloaded to implement the changes , and therefore the command below is used for the same



systemctl daemon-reload



• Next, the docker service needs to be restarted as well, the command used for the same is



systemctl restart docker

Docker Client:

• After the required setup in the Docker Host, Docker service, if running , needs to be stopped in this system, and could be done by following command:



systemctl stop docker



• Next, the IP of the Docker Host needs to be exported from this system using the DOCKER_HOST variable and export command is used for the same.



export DOCKER_HOST=<DOCKER_HOST_IP>:4243

Creation of Dockerfile for creation of Image to be used as an agent

• First of all , a Dockerfile is created for generation of image to be used as a Docker agent for Dynamic Jenkins Slave.



FROM centos

RUN yum install curl -y

RUN curl -LO "https://storage.googleapis.com/kubernetes-release/release/$(curl -s https://storage.googleapis.com/kubernetes-release/release/stable.txt)/bin/linux/amd64/kubectl"

RUN chmod +x kubectl

RUN mv kubectl /usr/bin

RUN mkdir /main/

RUN mkdir /root/web/

RUN mkdir /root/.kube/

COPY  ca.crt   /root/

COPY  client.crt  /root/

COPY  client.key  /root/

COPY .kube/  /root/.kube/

RUN kubectl config get-contexts

RUN yum install git -y

RUN yum install openssh-server java -y

RUN yum install java-1.8.0-openjdk -y

COPY docker.repo  /etc/yum.repos.d/

RUN yum install docker-ce --nobest -y

CMD killall firewalld -DFOREGROUND

CMD /usr/sbin/sshd -DFOREGROUND

CMD /usr/bin/dockerd -DFOREGROUND 

RUN ssh-keygen -A

EXPOSE 22

EXPOSE 8080

• Next, image could be build using the following command, also it is necessary to name the dockerfile as ‘Dockerfile’ for the command to execute successfully.



docker build -t image_name:version  /path/to/Dockerfile



• Also , the image generated needs to be pushed to public Docker registry like Docker Hub. So before executing the commands below , it is necessary to have an account in Docker Hub, the link for the same is present at the bottom of this README.



docker login -u <Docker Hub username>  -p <Docker Hub password>



• After login to Docker Hub using the CLI, tag operation needs to be performed before pushing the image , the reason being that the image name format should be /image_name:version, the command for the same is as follows:



docker tag image_name:version  <Docker Hub username>/image_name:version



• After tagging, the image could be pushed using the command below:



docker push <Docker Hub username>/image_name:version

Configuration of Dynamic Cloud with Docker Agent in Jenkins

• Cloud is the one that would launch the Dynamic Jenkins Slave, Jenkins is accessed from the system acting as the Docker Client.


• Before starting the configuration of Dynamic Cloud in Jenkins, Docker plugin should be installed and could be installed from Manage Plugins in the Manage Jenkins section.






Docker Plugin



• Clouds in Jenkins could be configured by accessing Manage Jenkins > Manage Nodes and Clouds > Configure Clouds.






Setting up Docker Host (Docker Client IP is mentioned above )







Docker(Slave) Agent Setup (The image specified is generated from the Dockerfile mentioned above)







Connect Method is SSH between Master and Slave, also the prerequisites mentioned needs to be satisfied by the Docker Image mentioned , other than this , SSH Key needs to generated and this requirements are satisfied and could be observed in the Dockerfile above.







Image Pull Strategy every time Jenkins Slave is created

Creation of Jenkins Slave Node Jobs

Some setup that are common for both jobs, is as follows:

• For both the job to run under the slave created dynamically, it should be restricted by placing the label that was mentioned during the configuration of dynamic cloud.






Here, kube-slave is the label used



• Next setup involves setting up GitHub hook triggers , and could be added using a webhook to the GitHub repo. For creation of webhook in the repo, public URL is required that could be generated using ngrok, using the concept of Tunneling.



./ngrok http 8080




Public URL using ngrok







Addition of Webhook to the GitHub repository

Job 1

• In this job ,certain program files needs to be obtained from SCM(Source Code Management) like GitHub in this case. Thereby GitHub repo URL needs to be specified in the Job itself.






Specification of GitHub repo and branch







Build Trigger for Job 1



• The script used for implementation of Job 1 is as follows :






Job 1 Shell Script



• The above script needs a Dockerfile(dfile_web) , which is shown below



FROM centos 
RUN yum install httpd -y 
COPY *.html  /var/www/html/ 
CMD /usr/sbin/httpd -DFOREGROUND 
EXPOSE 80/tcp



• The script builds the image for the Apache HTTPD Webserver using the Dockerfile above and tags to the format needed to push the image to DockerHub , and then it logins to DockerHub and pushes the tagged image.


• The local copy of image and the tagged image is removed to avoid conflict in case it gets triggered again due to changes in SCM.

Job 2

• This job is the downstream project for Job 1, the YAML file to set up Kubernetes deployment needs to be obtained from SCM, i.e., GitHub in this case. Here , the file is specified in different branch i.e., modify of the repository same as the one used by Job 1, the reason being to avoid copying unnecessary file.






Specification of GitHub repo and branch







Build Trigger for Job 2



• The script used for implementation of Job 2 is as follows:






Job 2 Shell Script



• The YAML file(kub_task4.yaml) required in the above file is shown below



apiVersion: apps/v1
kind: Deployment
metadata:  
  name: task4-deploy  
  labels:    
    app: kubapp
spec:  
  replicas: 1  
  selector:    
    matchLabels:      
      app: kubapp  
  template:    
    metadata:      
      labels:        
        app: kubapp    
    spec:      
      containers:       
       - name: task4-httpd          
         image: satyams1999/httpd_image:v1          
         imagePullPolicy: "Always"      
      nodeSelector:        
        kubernetes.io/hostname: minikube



• The Job 2 script creates a Kubernetes deployment using the above script and if deployment already exists , it performs rollout operations which updates the existing pod in the deployment(useful in cases where image is modified and needs to be implemented with zero downtime).


• Else, if deployment doesn’t exists already, it creates the deployment and expose it as well.

Output

Thank You 😃

Docker Hub Link

https://hub.docker.com/

LinkedIn Profile

https://www.linkedin.com/in/satyam-singh-95a266182