The Label Maker is a small Kubernetes controller that watches cluster nodes. It picks up the intended role of a node from a configurable role label and sets that role in a node-role.kubernetes.io/{role} label.
The kubelet allows to set node labels via the command line argument --node-labels. Starting with Kubernetes 1.16, it is for security reasons no longer allowed to set a node label of the form node-role.kubernetes.io/{role} for the role of the node the kubelet is running on (details). In the setup I'm working with, we create two types of cluster nodes -worker and infra- via autoscaling groups. In the cloud-init scripts of the nodes, we add --node-labels to the extra arguments of the kublet, and it contains node-role.kubernetes.io/{role} with the intended role. This no longer works and breaks a few things for us.
Once a node has joined the cluster, it's possible to set a node-role.kubernetes.io/{role} label via the API to anything you like, sufficient permissions provided. Now we could add an according kubectl command to the cloud-init script of the nodes. But that would require that we also provide a kubeconfig for API access there, which we don't want on those nodes. The idea for Label Maker was to set the node role in a different label and then have a controller copy that into a node-role.kubernetes.io/{role} label. That's really all that label-maker is doing.
The default for the node role label is node.kubernetes.io/role. It can be set via environment variable ROLE_LABEL. When the controller reconciles a node, it will check whether it already has any label of the form node-role.kubernetes.io/* set. If so, it does nothing for that node. Otherwise, if the role label is set, e.g. node.kubernetes.io/role=worker, it's value is added as a node-role.kubernetes.io/{role} label. For our example that would be node-role.kubernetes.io/worker=. Note that with this behavior, a later update to the role label would not update node-role.kubernetes.io. For this, it would have to be removed first.
There's an example manifest under deploy. A Docker image is hosted on DockerHub.
Even though Label-Maker isn't using any custom resources, and it's not truly an operator, it's built with the Operator-SDK. That's mostly for convenience. The Makefile has targets for building the binary and Docker image, and other stuff. Just run make to get a list. Note that for consistency, building is done inside a development container, so you will need Docker to build. The required development image is built the first time you invoke any of the build targets.