Kubernetes and Node Select

Kubernetes Label and NodeSelector Deployment

Show all the Nodes we have

root@kuberm:~/kube1.6config/deploy/webscale# kubectl get nodes
NAME             STATUS     AGE       VERSION
172.16.155.158   NotReady   129d      v1.6.0
172.16.155.165   NotReady   73d       v1.6.0
192.168.51.131   Ready      1d        v1.6.0
kubermnode1      Ready      128d      v1.6.0
kubermnode2      Ready      127d      v1.6.0

Setup a given node a label, said ebotrole=worker

kubectl label nodes kubermnode1 ebotrole=worker

delete the label

kubectl label nodes kubermnode1 ebotrole-

adding -, we can delete the node labeling.

Let's see the result

root@kuberm:~/kube1.6config/deploy/webscale# kubectl get nodes --show-labels
NAME             STATUS     AGE       VERSION   LABELS
172.16.155.158   NotReady   129d      v1.6.0    beta.kubernetes.io/arch=amd64,beta.kubernetes.io/os=linux,kubernetes.io/hostname=172.16.155.158
172.16.155.165   NotReady   73d       v1.6.0    beta.kubernetes.io/arch=amd64,beta.kubernetes.io/os=linux,kubernetes.io/hostname=172.16.155.165
192.168.51.131   Ready      1d        v1.6.0    beta.kubernetes.io/arch=amd64,beta.kubernetes.io/os=linux,kubernetes.io/hostname=192.168.51.131
kubermnode1      Ready      128d      v1.6.0    beta.kubernetes.io/arch=amd64,beta.kubernetes.io/os=linux,ebotrole=worker,kubernetes.io/hostname=kubermnode1
kubermnode2      Ready      127d      v1.6.0    beta.kubernetes.io/arch=amd64,beta.kubernetes.io/os=linux,kubernetes.io/hostname=kubermnode2

Yes, we set up a label, ebotrole=worker, in kubermnode1.

How to deploy a Pod to the labeled node

kubectl create -f label.yaml

where label.yaml

apiVersion: extensions/v1beta1
kind: Deployment
metadata:
  name: nginxstor
spec:
  #serviceName: "nginxstor"
  replicas: 2
  template:
    metadata:
      labels:
        app: nginxstor
      annotations:
        pod.alpha.kubernetes.io/initialized: "true"
    spec:
      affinity:
        podAntiAffinity:
          preferredDuringSchedulingIgnoredDuringExecution:
          - weight: 1
            podAffinityTerm:
              labelSelector:
                matchExpressions:
                - key: app
                  operator: In
                  values:
                  - nginxstor
              topologyKey: kubernetes.io/hostname
      containers:
      - name: nginxstor
        image: 192.168.51.130:5000/uwebserverv6
        ports:
          - containerPort: 8000
      nodeSelector:
        ebotrole: worker
  minReadySeconds: 5
  strategy:
    # indicate which strategy we want for rolling update
    type: RollingUpdate
    rollingUpdate:
      maxSurge: 1
      maxUnavailable: 1

See the nodeSelector

      nodeSelector:
        ebotrole: worker

Result

Now it will deploy to the node we setup as ebotrole: worker.
All the Pod will deploy to the node, if only one node, even is soft anti-affinity.

If we don't define the node label, the pod will be deployed until the host appeared.

root@kubecontext:~/k8sdeployex/labelselector# kubectl get po
NAME                        READY     STATUS    RESTARTS   AGE
nginxstor-293209922-2531z   0/1       Pending   0          23s
nginxstor-293209922-zdd83   0/1       Pending   0          23s