Kubernetes POD arguments are not passing to service, however Docker arguments are passing correctly

Question

Problem Statement:

I have a created a Docker image successfully from docker.io/joethecoder2/spring-boot-web. It has been tested with command line arguments, and those work correctly locally with Docker.

I am trying to pass java arguments that are passed to Docker to a Kubernetes POD that is defined with a single image docker.io/joethecoder2/spring-boot-web

The purpose of passing the arguments is to let the POD know what the IP address and port number are for the database service.

Problem Definition:

I have defined a Kubernetes POD here, however I believe the arguments are not passed correctly from singlePod.yaml when the POD is running the service.

Expected Result:

I expect that the Kubernetes POD be compatible with the Docker image defined here.

I expect that the Kubernetes POD accept arguments just like Docker does here:

docker run -it -p 8080:8080 joethecoder2/spring-boot-web -Dcassandra_ip=127.0.0.1 -Dcassandra_port=9042

curl -X POST --header 'Content-Type: application/json' --header 'Accept: text/plain' 'http://localhost:8080/restaurant/arguments'

Correct result is returned-> 127.0.0.1:9042

Wrong Result:

I know that the actual arguments are not passed to the POD, because when I run the following service, I receive no arguments returned.

curl -X POST --header 'Content-Type: application/json' --header 'Accept: text/plain' 'http://192.168.64.3:32308/restaurant/arguments'

Wrong result is returned-> :

Expected result -> 127.0.0.1:9042, as defined in the singlePod.yaml file

Why are the arguments missing, even though the POD definition file knows that the arguments have been defined staticly?

Answer 1

If you want to inject environment variable into the container.It's better to use ConfigMap so it provides flexibility as well as separation of concern.

apiVersion: v1
kind: Pod
metadata:
  name: spring-boot-web-demo
  labels:
    purpose: demonstrate-spring-boot-web
spec:
  containers:
  - name: spring-boot-web
    image: docker.io/joethecoder2/spring-boot-web
    command: ["java","-jar", "spring-boot-web-0.0.1-SNAPSHOT.jar"]
  env:
  - name: DCASSANDRA_IP
    valueFrom:
        configMapKeyRef:
            key: Dcassandra_ip
            name: env-values
  - name: DCASSANDRA_PORT
    valueFrom:
        configMapKeyRef:
            key: Dcassandra_port
            name: env-values
  restartPolicy: OnFailure

---
apiVersion: v1
kind: ConfigMap
metadata:
  name: env-values
data:
  Dcassandra_port=9042
  Dcassandra_ip=127.0.0.1

Now You need to write a Service Manifest file to expose this container in order to access it. I have attached links for further research.

ConfigMap

Service