Kubernetes Labels and Annotations

Internal

• Kubernetes Concepts

Labels

A label is a key/value pair contains identifying information used to organize and categorize (scope and select) objects.

Labels are used by selector queries, or within selector sections of object definitions. Replicaset controllers and services use selectors to identify the pods that fall under their scope.

Labels is a mechanism to define loose couplings.

The structure of keys and values is constrained, so they can be evaluated quickly.

TODO:

• https://kubernetes.io/docs/concepts/overview/working-with-objects/labels/
• Label syntax and character set: https://kubernetes.io/docs/concepts/overview/working-with-objects/labels/#syntax-and-character-set.

For a specific object declaration, the labels are specified in the metadata section of the manifest.

Annotations

https://kubernetes.io/docs/concepts/overview/working-with-objects/annotations/

An annotation contains non-identifying information. The information exposed by annotations is not used internally by Kubernetes. Is not queryable, cannot be used in selectors. The annotation keys and values are not constrained. Stored in .metadata.annotations.

apiVersion: apps/v1
kind: Deployment
spec:
  template:
    metadata:
      annotations:
        sidecar.istio.io/inject: "true"
...