# Ghost DaemonSet: Karpenter Node Overhead Reservation
#
# OVH Karpenter does NOT support kubelet.systemReserved in the NodePool CRD.
# Standard Karpenter uses pod resource *requests* from DaemonSets to simulate
# available capacity on a not-yet-provisioned node.
#
# The problem: Karpenter starts its simulation from raw flavor capacity (e.g.
# 3815 Mi for c3-4), but OVH's kubelet reserves a large chunk for system use.
# On c3-4: capacity=3815Mi, allocatable=1975Mi → OVH reserves 1840Mi.
# Karpenter doesn't know this and thinks 3815Mi is usable → picks nodes that
# are too small → infinite spin-up loop.
#
# Fix: this ghost DaemonSet reserves exactly (capacity - allocatable) so
# Karpenter's bin-packing simulation matches reality.
# Value is set from NODE_OVERHEAD_MI in env.variables (auto-calculated by the
# installer from a real node's capacity vs allocatable, or set manually).
#
# It targets only worker nodes (not the system node).
apiVersion: apps/v1
kind: DaemonSet
metadata:
  name: karpenter-node-overhead
  namespace: kube-system
  labels:
    app: karpenter-node-overhead
    purpose: karpenter-scheduling-simulation
spec:
  selector:
    matchLabels:
      app: karpenter-node-overhead
  updateStrategy:
    type: RollingUpdate
  template:
    metadata:
      labels:
        app: karpenter-node-overhead
    spec:
      nodeSelector:
        karpenter.sh/nodepool: workers
      tolerations:
      - key: node.kubernetes.io/not-ready
        operator: Exists
        effect: NoExecute
        tolerationSeconds: 300
      - key: node.kubernetes.io/unreachable
        operator: Exists
        effect: NoExecute
        tolerationSeconds: 300
      priorityClassName: system-node-critical
      terminationGracePeriodSeconds: 5
      containers:
      - name: overhead-placeholder
        image: gcr.io/pause-amd64:3.9
        command: ["/pause"]
        resources:
          requests:
            cpu: 2m
            # capacity - allocatable = OVH system reservation (auto-set by installer)
            memory: ${NODE_OVERHEAD_MI}Mi
          limits:
            cpu: 10m
            memory: ${NODE_OVERHEAD_MI}Mi