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.
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 labelbarwith the value of the existing labelfoo.--relabel=role=*:node-role.kubernetes.io/*=will add the labelnode-role.kubernetes.io/<role>=with the value of the existing labelrole.
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