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Envvar Configuration

This example will guide you through configuring environment variables within a Kubernetes Pod using a ConfigMap and a Secret. Make sure you have access to a Kubernetes cluster before proceeding. For various installation options, please refer to INSTALL.

First, let’s create a ConfigMap and a Secret, each containing one entry:

kubectl create configmap random-generator-config \
    --from-literal=PATTERN=EnvVarConfiguration \
    --from-literal="ILLEG.AL=Invalid Envvar name"
kubectl create secret generic random-generator-secret --from-literal=seed=11232156346

These resources will be used to define environment variables in a simple Pod declaration for our sample random-generator REST service:

kubectl create -f https://k8spatterns.io/EnvVarConfiguration/pod.yml

Inspecting the resource description reveals how the ConfigMap and Secret are used to set two environment variables, PATTERN and SEED, which are then exposed via the random-generator REST service.

To access the REST service, expose the Pod using the following command:

kubectl apply -f https://k8spatterns.io/EnvVarConfiguration/service.yml

For simplicity, this service exposes the service port via a nodePort. Assuming you are using Minikube, you can access the service from your desktop with the following:

minikube service random-generator --url > /tmp/random-url.txt &

This command starts a tunnel in the background and writes the access URLs for the exposed ports to a text file. Use the following command to access the service:

curl -s $(cat /tmp/random-url.txt)/info | jq .

  • Can you see how the environment variables are exposed?

  • What happens when you change the data of the ConfigMap or Secret (e.g., with kubectl edit cm random-generator-config)? Is the changed value reflected in response to your curl request?

  • What steps are necessary to display the updated value in the HTTP response?