K8S Node Label

K8S Node Label is a small tool to label Nodes based on their role in a kubernetes cluster.

Control Plane Node

Starting from 1.16 the --node-labels flag in kubelet is deprecated for security reasons. This tool runs inside the cluster and marks a node when it starts with the "node-role.kubernetes.io/control-plane" label.

Two more options are available:

• Exclude node from loadbalancing. When this feature is enabled a master node also gets excluded from loadbalancers created via "LoadBalancer"-Type Service.
• Exclude node from eviction. When this feature is enabled a master node also gets marked to exclude from eviction. "Master workloads will not be evicted if the master is NotReady for longer than the grace period" [1]

For more details please see: https://github.com/kubernetes/enhancements/blob/master/keps/sig-architecture/2019-07-16-node-role-label-use.md

[1] https://github.com/kubernetes/enhancements/blob/master/keps/sig-architecture/2019-07-16-node-role-label-use.md

Legacy master node support

Since kubernetes 1.20 taint and label node-role.kubernetes.io/master are deprecated. Cluster administrators should migrate both taints and labels to node-role.kubernetes.io/control-plane. During transition period you can control behaviour of K8s Node Label with 2 flags:

• -control-plane-legacy-label - if set to true will add node-role.kubernetes.io/master or node-role.kubernetes.io/spot-master label next to node-role.kubernetes.io/control-plane
• -control-plane-taint - by default K8s Node Label detects control-plane nodes by checking node-role.kubernetes.io/control-plane taint. Using this flag it can be switched to look for different flag (for example legacy: node-role.kubernetes.io/master)

Worker Node

To have a similar solution available for worker nodes it also marks worker nodes with the "node-role.kubernetes.io/worker" label.

Spot instances

Additionally this tool supports spot instance role to mark nodes in case they are based on spot instances. Therefore it assigns the "node-role.kubernetes.io/spot-worker" label to nodes, that are part of a spot request. Currently only aws is supported, but it can be extended. Pull requests for further providers are welcome :-)

Custom node-role labels

It is possible to label your nodes with role taken from custom label (for example custom-label). To enable this node use this tool with parameter custom-role-label equal to the name of that custom label. Then nodes with this custom-label will be also labelled with corresponding node-role.kubernetes.io/* label.

For example, node with custom-label=special-node will be also labelled with node-role.kubernetes.io/special-node.