node-relabeler

node-relabeler

About

This program watches for the changes in nodes of a Kubernetes cluster, and sets labels on them according to specs provided to it.

The original impetus for this project came from desire to label Kubernetes nodes with roles. If you label a node with the label node-role.kubernetes.io/<role>=, running kubectl get nodes with display the specified role in the ROLE column.

If you administer a Kubernetes cluster, it was possible to specify role assignments in the kubelet startup options. However, starting with Kubernetes 1.16, specifying node-role.kubernetes.io/<role>= is no longer allowed. The suggested workaround from the Kubernetes team is to label the nodes with some other, allowed label and run a worker that would apply node-role.kubernetes.io/<role>= to any nodes that are added or get updated with that other label. This project is intended to provide such functionality.

Running

When run, node-relabeler expects one or more re-labeling specifications provided in the command line:

node-relabeler --relabel=old/label=old-value:new/label=new-value

(multiple --relabel options may be provided). The program will watch for nodes being added or updated with labels that match the old-label=old-name pattern and if found, add the new/label=new-value label. Either old label name or value can contain a wildcard character * which will cause glob pattern matching. If * also shows up in the new label name or value, it will be replaced with the matched part of the old label.

For example,

• --relabel=foo=*:bar=* will add the label bar with the value of the existing label foo.
• --relabel=role=*:node-role.kubernetes.io/*= will add the label node-role.kubernetes.io/<role>= with the value of the existing label role.

Deploying

You can deploy node-relabeler into a Kubernetes cluster using a Helm chart provided with the project in charts/node-relabeler.

If you want to use Helm Operator, a sample Helm release object is available in deploy/helm-operator/release.yaml