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Rancher/Kubernetes Demo Application

This is a Go demo application used for demonstrating Kubernetes and load balancing.

It will create a colored icon for each replica within a ReplicaSet and indicate which one most recently served a response. Replicas which haven't been heard from will begin to fade out, until after a configurable number of seconds they will disappear. This is useful for demonstrating scaling up/down or in the case of an application like Rio, for showing scale-in of an upgraded application.

Environment Variables

  • TITLE: sets title in demo app
  • SHOW_VERSION: show version of app in ui (VERSION env var)
  • REFRESH_INTERVAL: interval in milliseconds for page to refresh (default: 1000)
  • EXPIRE_INTERVAL: how long a replica can go without being seen before we remove it from the display (default: 10s)
  • REMOVE_INTERVAL: how long after EXPIRE_INTERVAL until we remove the icon (default: 20s)
  • SKIP_ERRORS: set this to prevent errors from counting (useful on janky load balancers)
  • METADATA: extra text at bottom of info area
  • COW_COLOR: what color the cow background should be (default: black). Valid options are any color from the CSS pallete, including:
    • red
    • orange
    • yellow
    • olive
    • green
    • teal
    • blue
    • violet
    • purple
    • pink
    • black

Build

docker build -t monachus/rancher-demo .

Paths

By default the loaded page will reach back to /demo every REFRESH_INTERVAL and use the returned information to update the display. Other paths are:

  • /info - returns some additional information about the replica serving the request
  • /load - adds a 2s delay to the response from /info - use this for putting artificial load on the system and watching the replicas scale

Ports

The container will listen for traffic on port 8080.