Deploy WAR in Tomcat on Kubernetes

Question

I need to create a Multibranch Jenkins job to deploy a .war file in Tomcat that should run on Kubernetes. Basically, I need the following:

1. A way to install Tomcat on Kubernetes platform.
2. Deploy my war file on this newly installed Tomcat.

I need to make use of Dockerfile to make this happen.

PS: I am very new to Kubernetes and Docker stuff and need basic details as well. I tried finding tutorials but couldn't get any satisfactory article.

Any help will be highly highly appreciated.

Docker part

You can use the tomcat docker official image

In your Dockerfile just copy your war file in /usr/local/tomcat/webapps/ directory :

FROM tomcat

COPY app.war /usr/local/tomcat/webapps/

Build it :

docker build --no-cache -t <REGISTRY>/<IMAGE>:<TAG> .

Once your image is built, push it into a Docker registry of your choice.

docker push <REGISTRY>/<IMAGE>:<TAG>

Kubernetes part

1) Here is a simple kubernetes Deployment for your tomcat image

apiVersion: apps/v1
kind: Deployment
metadata:
  name: tomcat-deployment
  labels:
    app: tomcat
spec:
  replicas: 1
  selector:
    matchLabels:
      app: tomcat
  template:
    metadata:
      labels:
        app: tomcat
    spec:
      containers:
      - name: tomcat
        image: <REGISTRY>/<IMAGE>:<TAG>
        ports:
        - containerPort: 8080

This Deployment definition will create a pod based on your tomcat image.

Put it in a yml file and execute kubectl create -f yourfile.yml to create it.

2) Create a Service :

kind: Service
apiVersion: v1
metadata:
  name: tomcat-service
spec:
  selector:
    app: tomcat
  ports:
  - protocol: TCP
    port: 80
    targetPort: 8080

You can now access your pod inside the cluster with http://tomcat-service.your-namespace/app (because your war is called app.war)

3) If you have Ingress controller, you can create an Ingress ressource to expose the application outside the cluster :

apiVersion: extensions/v1beta1
kind: Ingress
metadata:
  name: tomcat-ingress
  annotations:
    nginx.ingress.kubernetes.io/rewrite-target: /
spec:
  rules:
  - http:
      paths:
      - path: /app
        backend:
          serviceName: tomcat-service
          servicePort: 80

Now access the application using http://ingress-controller-ip/app

Comments

[Akhil Prajapati]

Hi @Nicolas, Thanks a lot for your answer. I tried implementing this and at the end of the Jenkins Job, I am getting this: + kubectl --kubeconfig **** --namespace=dev-a apply -f k8s/services/ service "tomcat-service" created [Pipeline] sh + kubectl --kubeconfig **** --namespace=dev-a apply -f k8s/dev/ ingress "tomcat-ingress" created However, I don't see any new pod created when I run this: kubectl --kubeconfig=dev.us-east-1 --namespace=dev-a get pods

[Nicolas Pepinster]

Something is getting wrong probably. Type kube get events --sort-by lastTimestamp --namespace=dev-a to check the events relative to the new components created

[Akhil Prajapati]

should the ingress content and the deployment file be placed in different yaml?

[Nicolas Pepinster]

no you can put all in one yaml file. Check this example

[Akhil Prajapati]

The build is getting executed successfully but I am getting ImagePullBackOff error in pod. On describing the pod, I found this error: pull access denied for xyz/myrepo, repository does not exist or may require 'docker login'. However, I can see the image getting pushed with the same name. I also tried docker login but it didn't work.

[Nicolas Pepinster]

If you regsitry is secured, you need to create secret. After its creation, you need to reference the secret in your Deployment with imagePullSecrets instruction.