Microservice based Java Web App

Technology Stack used

• Java
• Servlet
• Maven
• Tomcat
• Jenkins
• Docker
• Kubernetes

Contents of the Repository

• Web Application made with Java Servlet
• pom.xml for maven to build the application and package it into a .jar
• Dockerfile which holds the steps to build a docker image of the web application
• Jenkinsfile to help Jenkins automate the building and deploying the web application into docker hub

Run the Web Application locally

git clone https://github.com/ariG23498/webapp_maven.git
cd webapp_maven
mvn package
cd target/bin/
./webapp

The web application is running on your localhost at post 9090

Go to your favorite web-browser and in the address bar type localhost:9090

CI/CD with Jenkins and Kubernetes Deployment

VM instance setup

In the following steps we will talk specifically of the Kubernetes cluster that has been created, the cluster consists of 2 VM instances one working as the master other as the worker. The VMs must be in same resource group and share the same virtual network. In each of the VMs we need to run the following block of codes.

setup_docker.sh

sudo apt-get remove docker docker-engine docker.io containerd runc

sudo apt-get update

sudo apt-get install -y \
    apt-transport-https \
    ca-certificates \
    curl \
    gnupg-agent \
    software-properties-common
    
curl -fsSL https://download.docker.com/linux/ubuntu/gpg | sudo apt-key add -

sudo apt-key fingerprint 0EBFCD88

sudo add-apt-repository \
   "deb [arch=amd64] https://download.docker.com/linux/ubuntu \
   $(lsb_release -cs) \
   stable"
   
sudo apt-get update

sudo apt-get install -y docker-ce docker-ce-cli containerd.io

cat > /etc/docker/daemon.json <<EOF
{
  "exec-opts": ["native.cgroupdriver=systemd"],
  "log-driver": "json-file",
  "log-opts": {
    "max-size": "100m"
  },
  "storage-driver": "overlay2"
}
EOF

mkdir -p /etc/systemd/system/docker.service.d

systemctl daemon-reload
systemctl restart docker

setup_kebernetes.sh

apt-get update && apt-get install -y apt-transport-https curl
curl -s https://packages.cloud.google.com/apt/doc/apt-key.gpg | apt-key add -
cat <<EOF >/etc/apt/sources.list.d/kubernetes.list
deb https://apt.kubernetes.io/ kubernetes-xenial main
EOF
apt-get update
apt-get install -y kubelet kubeadm kubectl
apt-mark hold kubelet kubeadm kubectl

Authorize Jenkins bye creating a new kubernetes service account and generating a base64 secret key:

authorize_jenkins.sh

kubectl -n webapp create sa jenkins
kubectl create clusterrolebinding jenkins --clusterrole cluster-admin --serviceaccount=webapp:jenkins
kubectl get -n webapp sa/jenkins --template='{{range .secrets}}{{ .name }} {{end}}' | xargs -n 1 kubectl -n webapp get secret --template='{{ if .data.token }}{{ .data.token }}{{end}}' | head -n 1 | base64 -d -

Save the secret as secret text credential for using kubernetes-cli-plugin with Jenkins.

Database setup

After setting up each VMs, we are creating a stateful persistent volume of 4 GiB for our MySQL database storage:

mysql-pv.yaml

apiVersion: v1
kind: PersistentVolume
metadata:
  name: mysql-pv-volume
  labels:
    type: local
spec:
  storageClassName: manual
  capacity:
    storage: 4Gi
  accessModes:
    - ReadWriteOnce
  hostPath:
    path: "/mnt/data"
---
apiVersion: v1
kind: PersistentVolumeClaim
metadata:
  name: mysql-pv-claim
spec:
  storageClassName: manual
  accessModes:
    - ReadWriteOnce
  resources:
    requests:
      storage: 4Gi

Now, we need to deploy the mysql:5.7 image as a deployment in the kubernetes cluster.

mysql-deployment.yaml

apiVersion: v1
kind: Service
metadata:
  name: mysql
spec:
  type: ClusterIP
  ports:
  - name: mysql
    port: 3306
    protocol: TCP
    targetPort: 3306
  selector:
    app: mysql
---
apiVersion: apps/v1
kind: Deployment
metadata:
  name: mysql
spec:
  selector:
    matchLabels:
      app: mysql
  strategy:
    type: Recreate
  template:
    metadata:
      labels:
        app: mysql
    spec:
      containers:
      - image: mysql:5.7
        name: mysql
        env:
          # Use secret in real usage
        - name: MYSQL_ROOT_PASSWORD
          value: Dare2@hack
        ports:
        - containerPort: 3306
          name: mysql
        volumeMounts:
        - name: mysql-persistent-storage
          mountPath: /var/lib/mysql
      volumes:
      - name: mysql-persistent-storage
        persistentVolumeClaim:
          claimName: mysql-pv-claim

Automation setup

Setup Jenkins as directed by Jenkins. For the CI/CD pipeline we had to authenticate Jenkins with GitHub, Docker Hub and Kubernetes. We have used the following deployment file to expose our webapp:

webapp-service-deploy.json

{
    "apiVersion": "v1",
    "kind": "Service",
    "metadata": {
        "name": "webapp-v$BUILD_NUMBER",
        "labels": {
            "run": "webapp-v$BUILD_NUMBER"
        },
        "namespace": "webapp"
    },
    "spec": {
        "externalIPs": [
            "104.211.230.185"
        ],
        "externalTrafficPolicy": "Cluster",
        "ports": [
            {
                "nodePort": 32607,
                "port": 9090,
                "protocol": "TCP",
                "targetPort": 9090
            }
        ],
        "selector": {
            "run": "webapp-v$BUILD_NUMBER"
        },
        "sessionAffinity": "None",
        "type": "LoadBalancer"
    },
    "status": {
        "loadBalancer": {}
    }
}

The rest of the CI/CD pipeline is taken care of by Jenkins. ❤️