Label, Selector, Annotation

Labels & Selectors

• Lables: properties attached to each item. Take the following pod.yaml for example:

  apiVersion: v1
  kind: Pod
  metadata:
  name: webapp
  labels:
    app: web
    env: prod
  

• Selectors: Filters for labels.
• You can use labels and selectors to group objects.
• Command: kubectl get pods --selector env=prod
• Example: replicaSet:

  apiVersion: apps/v1
  kind: ReplicaSet
  metadata:
  name: webapp
  labels:
    app: frontend
    env: prod
  spec:
  replicas: 3
  selector:
    matchLabels:
      app: frontend <- match pod's label
    template:
      metadata:
        labels:
          app: frontend
          env: prod
    spec:
      containers:
      - name: myweb
        image: myweb
  

Annotations:

• Record details, e.g., version, for intergration purpose.