kubectl label seçeneği

label Neden Lazım

Worker'lara label verilerek bazı podların bu label'a sahip worker'da çalışması sağlanır.

Pod'u worker'a atamak için 2 yöntem var

1. nodeSelector

2. nodeAffinity

Açıklaması şöyle

nodeSelector — This is a simple Pod scheduling feature that allows scheduling a Pod onto a node whose labels match the nodeSelector labels specified by the user.

Node Affinity — This is the enhanced version of the nodeSelector introduced in Kubernetes 1.4 in beta. It offers a more expressive syntax for fine-grained control of how Pods are scheduled to specific nodes.

Inter-Pod Affinity — This feature addresses the third scenario above. Inter-Pod affinity allows co-location by scheduling Pods onto nodes that already have specific Pods running.

Worker Node'a label Vermek

Söz dizimi şöyle

kubectl label nodes <nodename> mylabel=somevalue

Örnek

Şöyle yaparız

kubectl label node minikube foo=bar

Worker Node'a Verilen Label'ları Listelemek

Şöyle yaparız

kubectl get nodes --show-labels

1. nodeSelector

Örnek

Şöyle yaparız

kubectl label nodes host02 disktype=ssd
node “host02” labeled

Şöyle yaparız

apiVersion: v1
kind: Pod
metadata:
  name: httpd
  labels:
    env: prod
spec:
  containers:
  - name: httpd
    image: httpd
    imagePullPolicy: IfNotPresent
  nodeSelector:
    disktype: ssd

Örnek - Yanlış Kullanım

Şöyle yaparız

apiVersion: v1
kind: Pod
metadata:
  <snip>
spec:
  affinity:
    nodeAffinity:
      requiredDuringSchedulingIgnoredDuringExecution:
        nodeSelectorTerms:
        - matchExpressions:
          - key: topology.kubernetes.io/region
            operator: In
            values:
            - ca-central-1
  <snip>
  nodeSelector:
    topology.kubernetes.io/zone: "ca-central-1a"
    topology.kubernetes.io/zone: "ca-central-1b"

Açıklaması şöyle

All nodeSelectors must be matched. Node labels can only have a single value. Perhaps the developer thought that nodeSelectors were ORed and not ANDed, or perhaps this was just a careless mistake. Either way, Kubernetes is doing exactly what you told it to do by not scheduling the Pod on any worker, because the scheduling instructions were impossible to satisfy.

2. nodeAffinity

nodeAffinity yazısına taşıdım