tomcat-kubernetes

What is needed to create a Tomcat Docker image to run a cluster of tomcats in Kubernetes.

Get the latest tomcat snapshot of tomcat from the ASF tomcat repo:

git clone https://github.com/apache/tomcat.git
cd modules/stuffed
mvn clean
mvn install

Build the Docker image:

podman build -t quay.io/${USER}/tomcat-stuffed
podman login quay.io/${USER}/tomcat-stuffed
podman push quay.io/${USER}/tomcat-stuffed

This tomcat image can used to prepare a custom image with you webapp (here sample.war)

cd $HOME
git clone https://github.com/jfclere/tomcat-kubernetes.git 
cd tomcat-kubernetes
podman build -f Dockerfile.webapp -t quay.io/${USER}/tomcat-in-the-cloud-war --build-arg war=/sample.war --build-arg IMAGE=quay.io/${USER}/tomcat-stuffed .

Push the image on docker

podman login quay.io/${USER}/tomcat-in-the-cloud-war
podman push quay.io/${USER}/tomcat-in-the-cloud-war

For OpenShift https://manage.openshift.com/account/index use add a New Plan (Starter is enough) creating the plan takes a while... open the web console and create project On the left of the console you can get the login command ("Copy Login Command"). Use it on you laptop to connect.

oc login https://blabla --token=blabla

Use the project you have created (in my case I have created tomcat-in-the-cloud)

oc project tomcat-in-the-cloud

Add the user to view the pods

oc policy add-role-to-user view system:serviceaccount:tomcat-in-the-cloud:default -n tomcat-in-the-cloud

Create the first pod ajust tomcat-in-the-cloud.yaml like:

apiVersion: apps/v1
kind: Deployment
metadata:
  name: tomcat-in-the-cloud
  labels:
    app: tomcat-in-the-cloud
spec:
  replicas: 1
  selector:
    matchLabels:
      app: tomcat-in-the-cloud
  template:
    metadata:
      labels:
        app: tomcat-in-the-cloud
    spec:
      containers:
      - name: tomcat-in-the-cloud
        image: quay.io/jfclere/tomcat-in-the-cloud
        ports:
        - containerPort: 8080
        env:
        - name: OPENSHIFT_KUBE_PING_NAMESPACE
          value: "tomcat-in-the-cloud"
        - name: ENV_FILES
          value: "/opt/usekube.sh"

start it:

kubectl create -f tomcat-in-the-cloud.yaml

Scale it do 2 replicas

kubectl scale deployment tomcat-in-the-cloud --replicas=2

Expose the deployment

kubectl expose deployment tomcat-in-the-cloud --type=LoadBalancer --port 80 --target-port 8080

Use the console to create the route then change it to make it not sticky and session less, lastly edit the yaml and save it. Something like

apiVersion: route.openshift.io/v1
kind: Route
metadata:
  annotations:
    haproxy.router.openshift.io/balance: roundrobin
    haproxy.router.openshift.io/disable_cookies: 'true'
    openshift.io/host.generated: 'true'
    ...

The route will be modified when you save it. To access to the tomcat use the hostname something like http://tomcat-in-the-cloud-tomcat-in-the-cloud.193b.starter-ca-central-1.openshiftapps.com/

You can also use:

kubectl get services
NAME                  TYPE           CLUSTER-IP      EXTERNAL-IP                         PORT(S)        AGE
tomcat-in-the-cloud   LoadBalancer   172.21.33.123   ad04ef07-eu-de.lb.appdomain.cloud   80:32475/TCP   31s

Here use http://ad04ef07-eu-de.lb.appdomain.cloud/sample/ to reach the application