The Label That Kubernetes Removed — JavaScript Bug Hunt

Briefing

Modelled on Reddit's Pi-Day outage (14 March 2023): a Kubernetes upgrade to 1.24 removed the long-deprecated master node label. Calico's route calculation still keyed on it, so the cluster's network layer silently misrouted and the site was down for several hours.

topology.js reads only the legacy label and has no fallback.

Fix roleOf so the modern label is honoured and the legacy one remains a fallback.

Bug report

BUG-REDDIT314 · Priority: Critical · Reported by: compute

roleOf(node) must return the node's role, preferring the modern label:

• "node-role.kubernetes.io/control-plane" wins if present
• otherwise the legacy "node-role.kubernetes.io/master"
• otherwise "worker"

Observed: after the upgrade only the legacy key exists on old nodes and only the modern key on new ones. Reading one key alone mislabels half the cluster.

Logs

[topology] node ip-10-0-3-14 role=worker (expected control-plane)
[topology] route table built from 0 control-plane nodes

The code as shipped

src/k8s/topology.js (editable)

// Determines a node's role from its labels.
exports.roleOf = function (node) {
  if (node.labels["node-role.kubernetes.io/master"] !== undefined) {
    return "control-plane";
  }
  return "worker";
};

Read-only context: src/k8s/LABELS.js.