k8s-topology-spread-constraints

link

• https://kubernetes.io/zh-cn/docs/concepts/scheduling-eviction/topology-spread-constraints/
• https://kubernetes.io/docs/concepts/workloads/pods/pod-topology-spread-constraints/

集群级别的默认约束

内置默认约束

defaultConstraints:

  - maxSkew: 3
    topologyKey: "kubernetes.io/hostname"
    whenUnsatisfiable: ScheduleAnyway
  - maxSkew: 5
    topologyKey: "topology.kubernetes.io/zone"
    whenUnsatisfiable: ScheduleAnyway

sample

• 6 node in 3 az
• 1.25

nginx deployment

apiVersion: apps/v1
kind: Deployment
metadata:
  creationTimestamp: null
  labels:
    app: nginx
  name: nginx
spec:
  replicas: 5
  selector:
    matchLabels:
      app: nginx
  strategy: {}
  template:
    metadata:
      creationTimestamp: null
      labels:
        app: nginx
    spec:
      topologySpreadConstraints:

      - maxSkew: 1
        topologyKey: "kubernetes.io/hostname"
        whenUnsatisfiable: DoNotSchedule
        labelSelector:
          matchLabels:
            app: nginx
      containers:
      - image: nginx
        name: nginx
        resources: {}
status: {}

pod

kind: Pod
apiVersion: v1
metadata:
  name: mypod
  labels:
    app: nginx
spec:
  topologySpreadConstraints:

  - maxSkew: 1
    # topologyKey: "kubernetes.io/hostname"
    topologyKey: "topology.kubernetes.io/zone"
    whenUnsatisfiable: DoNotSchedule
    labelSelector:
      matchLabels:
        app: nginx
  containers:
  - name: pause
    image: registry.k8s.io/pause:3.1

result

• for zone
  

• for hostname
  check up topology in previous diagram