anton-fedorov / k8s-labeler

⚓️ Apply labels to Kubernetes pods on startup

k8s-labeler

Intended to be used as an init container for a Kubernetes pod.

Usage

The KUBE_NAMESPACE env var is required. This must match the namespace of the pod you're running in.

Any env vars containing KUBE_LABEL_ will be applied to the pod as labels via the API. For example:

KUBE_LABEL_hostname=foobar

Would result in a label hostname: foobar on the pod.

This can be useful for setting properties from the Downward API as labels (e.g. exposing a unique label for each pod in a stateful).

Run locally

./run.sh

Kubernetes example

This init container sets a hostname label equal to the pod's name:

initContainers:
  - image: devth/k8s-labeler
    name: labeler
    env:
      - name: KUBE_NAMESPACE
        valueFrom:
          fieldRef:
            fieldPath: metadata.namespace
      - name: KUBE_LABEL_hostname
        valueFrom:
          fieldRef:
            fieldPath: metadata.name

Inspect the pod with:

kubectl get pod -l app=myapp --show-labels

NAME                     READY     STATUS    RESTARTS   AGE       LABELS
myapp-2768796676-c702s   2/2       Running   0          25m       app=myapp,hostname=myapp-2768796676-c702s,pod-template-hash=2768796676

And notice that the hostname=myapp-2768796676-c702s label is present.

License

Copyright 2017 Trevor C. Hartman

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.