App settings

The app reads its settings from environment variables. The Helm chart sets them for you from its values. Use them directly when you run the image another way: with docker run, in your own manifests, or by patching the release file with Kustomize.

Variable	Default	What it does
MESSAGE	Hello world!	The message on the page. Chart value: message.
PORT	8080	The port the app listens on. Chart value: deployment.container.port.
HANDLER_PATH_PREFIX	none	The path the app serves under, such as /app/hello. Set it when the proxy passes the prefix on. Chart value: pathPrefix, when rewritePath is false.
RENDER_PATH_PREFIX	none	The path the page’s links use, so the browser asks the proxy for the stylesheet and images under the prefix. Chart value: pathPrefix.
KUBERNETES_NAMESPACE	-	The namespace shown on the page. The chart sets it from the pod.
KUBERNETES_POD_NAME	the host name	The pod shown on the page. The chart sets it from the pod.
KUBERNETES_NODE_NAME	-	The node shown on the page, with its operating system and kernel. The chart sets it from the pod.
CONTAINER_IMAGE	the app’s image	The image shown on the page. Chart value: deployment.container.image.*.
LOG_LEVEL	info	The log level, such as debug, info, warn or error. At debug, the app logs its settings when it starts.

Leading and trailing slashes in the two path prefixes are optional. The page also shows the image’s architecture, such as linux/amd64, which the app reads from itself.

The pod details

The chart sets the three KUBERNETES_ variables with the Downward API. In your own manifest:

deployment.yaml (part)

env:
  - name: KUBERNETES_NAMESPACE
    valueFrom:
      fieldRef:
        fieldPath: metadata.namespace
  - name: KUBERNETES_POD_NAME
    valueFrom:
      fieldRef:
        fieldPath: metadata.name
  - name: KUBERNETES_NODE_NAME
    valueFrom:
      fieldRef:
        fieldPath: spec.nodeName

Run it with Docker

Terminal

docker run --rm -p 8080:8080 -e MESSAGE="Hello from Docker" paulbouwer/hello-kubernetes:1.11.0

Open http://localhost:8080/. You see Hello from Docker, with - for the namespace and node, and the container ID as the pod. Press Ctrl+C to stop.

What the app serves

Path	What
/	The page. Under a prefix, <prefix>/.
/css/, /images/, /fonts/, /favicon.ico	The stylesheet, the logo, the Ubuntu font and its licence, and the icon.

There is no separate health endpoint. The chart’s probes ask for the page.