Hello Node Example

This is a very simple Node.js example used to demonstrate how to...

• Consume configuration with dotenv from a specific location in the filesystem
• Package a Node.js app in a container image
• Deploy the image in Kubernetes

The following instructions assume that you have all of the prerequisite components (e.g., a Kubernetes cluster, Docker, Skaffold, Node, etc) installed and ready.

Run the application

To run the application (as a non-image), simply use node:

$ node index.js

Then using curl in a separate window make a request to the application:

$ curl localhost:8080/hello
Hello world

Create an image

The provided Dockerfile enables you to create an image with docker build:

$ docker build -t hellonode:v1 .

Then you can run the image with docker run:

$ docker run hellonode:v1

Deploy to Kubernetes

The provided deployment/service manifest (in k8s/deploy.yaml) and Skaffold manifest (skaffold.yaml) make it easy to build and deploy to Kubernetes using the skaffold command line:

$ skaffold dev

This builds the image and puts Skaffold into "dev" mode (which means it will watch for changes and rebuild/redeploy if any are detected).

The service that is created exposes the application's port through port 31234. Therefore, you can create a port-forward through to application with the following kubectl command:

$ kubectl port-forward kubectl port-forward service/hello-node-svc 8080:31234

Then, in a separate terminal window you can send a request to the app using curl:

$ curl localhost:8080/hello
Hello world

Configuring with a ConfigMap or Secret

To configure the greeting message with a ConfigMap or Secret, first create the ConfigMap or Secret containing the .env file. For example:

$ kubectl create secret generic greetingconfig --from-file .env

Then uncomment the lines in k8s/deploy.yaml that mount that secret:

    spec:
      containers:
      - name: hello-node-container
        image: hellonode:0.0.1-SNAPSHOT
        volumeMounts:
        - name: greeting-config
          mountPath: /etc/config
      volumes:
      - name: greeting-config
        secret:
          secretName: greetingconfig

If Skaffold is still running in "dev" mode, this change should trigger a rebuild/redeploy. If not, then run Skaffold in "dev" mode again to deploy the application with these new changes. You'll also need to reestablish the port forward because it won't survive a pod restart.