Node labels

How topology labels work

When running a Kubernetes cluster in multiple datacenters, it’s important to know when you want to schedule workloads close to each other (for example, a database and a backend application) or when you want to spread them out (for example, multiple replicas of frontend, or database replicas, or volume replicas). The first step to achieving this is to label Kubernetes nodes. Public clouds typically use the zone and region terms. In Kubernetes, the most common way to designate a geographical location is to use topology.kubernetes.io/zone and topology.kubernetes.io/region labels (or only the zone one).

Talos example

While labels are usually set manually in other Kubernetes distributions, with Talos you can describe the topology as code.

Example talm configuration:

values.yaml:

nodes:
  node1:
    labels:
      topology.kubernetes.io/zone: "us-west-1"
      topology.kubernetes.io/region: "us-west"
  node2:
    labels:
      topology.kubernetes.io/zone: "us-east-1"
      topology.kubernetes.io/region: "us-east"

_helpers.tpl:

{{- $nodeLabels := .Values.nodes | dig (include "talm.discovered.hostname" .) "labels" nil }}
machine:
  {{- with $nodeLabels }}
  nodeLabels:
    {{- toYaml . | nindent 4 }}
  {{- end }}