Start sprinboot in minkube with custom context url as environnement variable

Question

I have a springboot app which I want to deploy on Kubernetes (I'm using minikube) with a custom context path taken from the environment variables.

I've compiled an app.war file. exported an environment variable in Linux as follow:

export SERVER_SERVLET_CONTEXT_PATH=/app

And then started my app on my machine as follow:

java -jar app.war --server.servlet.context-path=$(printenv CONTEXT_PATH)

and it works as expected, I can access my app throw browser using the url localhost:8080/app/

I want to achieve the same thing on minikube so I prepared those config files:

---

• Dockerfile:

  FROM openjdk:8
  ADD app.war app.war
  EXPOSE 8080
  ENTRYPOINT ["java", "-jar", "app.war", "--server.servlet.context-path=$(printenv CONTEXT_PATH)"]
  

---

• deployment config file:

  apiVersion: apps/v1
  kind: Deployment
  metadata:
    name: esse-deployment-1
    labels:
      app: esse-1
  spec:
    replicas: 1
    selector:
      matchLabels:
        app: esse-1
    template:
      metadata:
        labels:
          app: esse-1
      spec:
        containers:
        - image: mysql:5.7
          name: esse-datasource
          ports:
          - containerPort: 3306
          env: 
          - name: MYSQL_ROOT_PASSWORD
            value: root 
        - image: esse-application
          name: esse-app
          imagePullPolicy: Never
          ports:
          - containerPort: 8080
          env:
          - name: server.servlet.context-path
            value: /esse-1
        volumes:
          - name: esse-1-mysql-persistent-storage
            persistentVolumeClaim:
              claimName: mysql-persistent-storage-claim
  
  ---
  
  apiVersion: v1
  kind: Service
  metadata:
    name: esse-service-1
    labels:
      app: esse-1
  spec:
    selector:
      app: esse-1
    ports:
      - protocol: TCP
        port: 8080
        targetPort: 8080
    type: NodePort
  

However, the java container inside the pod fails to start and here's the exception is thrown by spring:

Initialization of bean failed; nested exception is java.lang.IllegalArgumentException: ContextPath must start with '/' and not end with '/'

Answer 1

Make use of configmaps.

The configmap will holds application.properties of your springboot application.

---
apiVersion: v1
kind: ConfigMap
metadata:
  name: esse-config
data:
  application-dev.properties: |
    spring.application.name=my-esse-service
    server.port=8080
    server.servlet.context-path=/esse-1

NOTE: server.servlet.context-path=/esse-1 will override context-path of your springboot application.

Now refer this configmap in your deployment yaml.

---
apiVersion: apps/v1
kind: Deployment
metadata:
  name: esse-deployment-1
  labels:
    app: esse-1
spec:
  replicas: 1
  selector:
    matchLabels:
      app: esse-1
  template:
    metadata:
      labels:
        app: esse-1
    spec:
      containers:
      - image: mysql:5.7
        name: esse-datasource
        ports:
        - containerPort: 3306
        env: 
        - name: MYSQL_ROOT_PASSWORD
          value: root 
      - image: esse-application
        name: esse-app
        imagePullPolicy: Never
        command: [ "java", "-jar", "app.war", "--spring.config.additional-location=/config/application-dev.properties" ]
        ports:
        - containerPort: 8080
        volumeMounts:
        - name: esse-application-config
          mountPath: "/config"
          readOnly: true
      volumes:
      - name: esse-application-config
        configMap:
          name: esse-config
          items:
          - key: application-dev.properties
            path: application-dev.properties
      - name: esse-1-mysql-persistent-storage
        persistentVolumeClaim:
          claimName: mysql-persistent-storage-claim

NOTE: Here we are mounting configmap inside your springboot application container at /config folder. Also --spring.config.additional-location=/config/application-dev.properties is pointing to the application.properties config file.

In future if you want to add any new config or update the value of existing config that just make the change in configmap and kubectl apply it. Then to reflect those new config changes, just scale down and scale up the deployment.

Hope this helps.

Answer 2

Finally, I found a solution.

I configured my application to startup with a value for the context path taken from the environment variables by adding this line inside my application.properties:

server.servlet.context-path=${ESSE_APPLICATION_CONTEXT}

And the rest remains as it was, means I'm giving the value of the variable ESSE_APPLICATION_CONTEXT throw the config

env:
- name: ESSE_APPLICATION_CONTEXT
  value: /esse-1

And then starting the application without the --server.servlet.context-path parameeter, which means like that:

java -jar app.war

NOTE: as pointed by @mchawre's answer, it's also possible to make use of ConfigMap as documented in Kubernetes docs.

Answer 3

Looks like what you want is SERVER_SERVLET_CONTEXT_PATH variable defined in your container spec:

apiVersion: apps/v1
kind: Deployment
metadata:
  name: esse-deployment-1
  labels:
    app: esse-1
spec:
  replicas: 1
  selector:
    matchLabels:
      app: esse-1
  template:
    metadata:
      labels:
        app: esse-1
    spec:
      containers:
      - image: mysql:5.7
        name: esse-datasource
        ports:
        - containerPort: 3306
        env: 
        - name: MYSQL_ROOT_PASSWORD
          value: root 
      - image: esse-application
        name: esse-app
        imagePullPolicy: Never
        ports:
        - containerPort: 8080
        env:
        - name: SERVER_SERVLET_CONTEXT_PATH  <== HERE
          value: /esse-1
      volumes:
        - name: esse-1-mysql-persistent-storage
          persistentVolumeClaim:
            claimName: mysql-persistent-storage-claim

Note that in your Pod spec you are using /esse-1 while on your local setup you have /app