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‎Dockerfile

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FROM golang:1.13 as builder
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ARG KUBECONFIG
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ARG NODE_NAME
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ENV GO111MODULE=on
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WORKDIR /app
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COPY go.mod .
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COPY go.sum .
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RUN go mod download
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COPY . .
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RUN CGO_ENABLED=0 GOOS=linux go build
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FROM scratch
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COPY --from=builder /app/k8s-node-label-monitor /app/
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ENTRYPOINT [ "/app/k8s-node-label-monitor" ]

‎LICENSE

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Apache License
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Version 2.0, January 2004
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http://www.apache.org/licenses/
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TERMS AND CONDITIONS FOR USE, REPRODUCTION, AND DISTRIBUTION
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limitations under the License.

‎README.md

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# Kubernetes Node Label Monitor
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This tool provides a custom Kubernetes controller for monitoring and notifying changes in the label states of Kubernetes
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nodes (labels added, deleted, or updated), and can be run either node-local or cluster-wide. Notifications can be
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dispatched to a number of different targets, and can be easily extended or customized through a simple notification
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interface.
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## Installation
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If planning to use the CLI App directly, e.g. for node-local testing, this can be compiled and installed as other Go
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projects:
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```
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$ go get github.com/adaptant-labs/k8s-node-label-monitor
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```
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For Docker containers and Kubernetes deployment instructions, see below.
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## Usage
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General usage is as follows:
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```
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$ k8s-node-label-monitor --help
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Node Label Monitor for Kubernetes
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Usage: k8s-node-label-monitor [flags]
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-kubeconfig string
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Paths to a kubeconfig. Only required if out-of-cluster.
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-l Only track changes to the local node
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-n string
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Notification endpoint to POST updates to
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```
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### Running Node-Local via Docker
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Multi-arch Docker images are available on Docker Hub at [adaptant/k8s-node-label-monitor]. These may be run as-is
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in-cluster, or out of cluster with an appropriate `KUBECONFIG` passed through.
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### Running as a Kubernetes Deployment (Cluster-wide Monitoring)
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An example Deployment configuration for cluster-wide monitoring and notification is provided in
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`k8s-node-label-monitor-cluster-deployment.yaml`, which can be, as the name implies, directly applied to the running
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cluster:
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```
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$ kubectl apply -f https://raw.githubusercontent.com/adaptant-labs/k8s-node-label-monitor/k8s-node-label-monitor-cluster-deployment.yaml
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```
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This will create a single Deployment constrained to running on the Kubernetes master. It will further create a special
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`node-label-monitor` service account, cluster role, and binding with the permission to list and watch nodes.
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53+
### Running as a Kubernetes DaemonSet (Node-Local Monitoring)
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An example DaemonSet configuration for node-local monitoring and notification is provided in
56+
`k8s-node-label-monitor-cluster-deployment.yaml`, which can be applied directly:
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```
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$ kubectl apply -f https://raw.githubusercontent.com/adaptant-labs/k8s-node-label-monitor/k8s-node-label-monitor-node-local-daemonset.yaml
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```
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This will create a DaemonSet that will run on each node, with each node monitoring and notifying changes to its own
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label state directly. It will further create a special `node-label-monitor` service account, cluster role, and binding
64+
with the permission to list and watch nodes.
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## Notification Plugins
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Notification targets are provided through easily-extensible plugins. At present, the following notification mechanisms
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are supported:
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| Notifier | Description |
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|----------|-------------|
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| Logger | Log-based notification, piggybacking on the default logger instance |
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| REST API Endpoint | POSTs the JSON-encoded payload to a defined REST API endpoint |
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## Features and bugs
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Please file feature requests and bugs in the [issue tracker][tracker].
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80+
## Acknowledgements
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This project has received funding from the European Union’s Horizon 2020 research and innovation programme under grant
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agreement No 825480 ([SODALITE]).
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## License
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`k8s-node-label-monitor` is licensed under the terms of the Apache 2.0 license, the full version of which can be found
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in the LICENSE file included in the distribution.
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[SODALITE]: https://www.sodalite.eu
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[tracker]: https://github.com/adaptant-labs/k8s-node-label-monitor/issues
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[adaptant/k8s-node-label-monitor]: https://hub.docker.com/repository/docker/adaptant/k8s-node-label-monitor

‎go.mod

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module github.com/adaptant-labs/k8s-node-label-monitor
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go 1.13
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require (
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github.com/go-logr/logr v0.1.0
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k8s.io/api v0.18.3
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k8s.io/apimachinery v0.18.3
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k8s.io/client-go v0.18.2
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sigs.k8s.io/controller-runtime v0.6.0
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)

‎go.sum

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Large diffs are not rendered by default.

‎k8s-node-label-monitor-cluster-deployment.yaml

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kind: ServiceAccount
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apiVersion: v1
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metadata:
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name: node-label-monitor
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namespace: kube-system
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---
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kind: ClusterRole
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apiVersion: rbac.authorization.k8s.io/v1
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metadata:
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name: system:node-label-monitor
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rules:
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- apiGroups: [""]
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resources: ["nodes"]
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verbs: ["list", "watch"]
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---
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kind: ClusterRoleBinding
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apiVersion: rbac.authorization.k8s.io/v1
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metadata:
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name: system:node-label-monitor
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subjects:
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- kind: ServiceAccount
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name: node-label-monitor
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namespace: kube-system
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roleRef:
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kind: ClusterRole
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name: system:node-label-monitor
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apiGroup: rbac.authorization.k8s.io
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---
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apiVersion: apps/v1
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kind: Deployment
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metadata:
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labels:
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app: node-label-monitor
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name: node-label-monitor
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namespace: kube-system
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spec:
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replicas: 1
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selector:
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matchLabels:
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app: node-label-monitor
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template:
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metadata:
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labels:
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app: node-label-monitor
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spec:
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serviceAccount: node-label-monitor
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affinity:
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nodeAffinity:
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preferredDuringSchedulingIgnoredDuringExecution:
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- weight: 1
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preference:
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matchExpressions:
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- key: "node-role.kubernetes.io/master"
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operator: In
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values: [""]
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tolerations:
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- key: "node-role.kubernetes.io/master"
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operator: "Equal"
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value: ""
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effect: "NoSchedule"
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containers:
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- env:
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- name: NODE_NAME
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valueFrom:
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fieldRef:
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fieldPath: spec.nodeName
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image: adaptant/k8s-node-label-monitor:latest
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name: node-label-monitor

‎k8s-node-label-monitor-node-local-daemonset.yaml

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kind: ServiceAccount
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apiVersion: v1
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metadata:
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name: node-label-monitor
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namespace: kube-system
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---
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kind: ClusterRole
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apiVersion: rbac.authorization.k8s.io/v1
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metadata:
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name: system:node-label-monitor
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rules:
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- apiGroups: [""]
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resources: ["nodes"]
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verbs: ["list", "watch"]
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---
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kind: ClusterRoleBinding
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apiVersion: rbac.authorization.k8s.io/v1
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metadata:
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name: system:node-label-monitor
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subjects:
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- kind: ServiceAccount
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name: node-label-monitor
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namespace: kube-system
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roleRef:
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kind: ClusterRole
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name: system:node-label-monitor
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apiGroup: rbac.authorization.k8s.io
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---
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apiVersion: apps/v1
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kind: DaemonSet
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metadata:
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labels:
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app: node-label-monitor
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name: node-label-monitor
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namespace: kube-system
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spec:
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selector:
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matchLabels:
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app: node-label-monitor
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template:
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metadata:
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labels:
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app: node-label-monitor
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spec:
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serviceAccount: node-label-monitor
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containers:
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- env:
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- name: NODE_NAME
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valueFrom:
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fieldRef:
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fieldPath: spec.nodeName
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image: adaptant/k8s-node-label-monitor:latest
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name: node-label-monitor
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args:
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# Run in node-local mode
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- "-l"

‎main.go

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package main
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import (
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"flag"
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"fmt"
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"github.com/adaptant-labs/k8s-node-label-monitor/notifiers"
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v1 "k8s.io/api/core/v1"
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metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
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"k8s.io/apimachinery/pkg/fields"
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"k8s.io/apimachinery/pkg/util/wait"
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"k8s.io/client-go/kubernetes"
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"k8s.io/client-go/tools/cache"
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"k8s.io/client-go/util/workqueue"
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"os"
15+
"sigs.k8s.io/controller-runtime/pkg/client/config"
16+
logf "sigs.k8s.io/controller-runtime/pkg/log"
17+
"sigs.k8s.io/controller-runtime/pkg/log/zap"
18+
"time"
19+
)
20+
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var (
22+
monitorName = "k8s-node-label-monitor"
23+
nodeLocal = false
24+
log = logf.Log.WithName(monitorName)
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nodeLabels = map[string]map[string]string{}
26+
)
27+
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type Controller struct {
29+
indexer cache.Indexer
30+
queue workqueue.RateLimitingInterface
31+
informer cache.Controller
32+
notifier notifiers.LabelNotifier
33+
}
34+
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// Compare two label maps and determine which key/value pairs have been added, deleted, or updated.
36+
func compareLabelMaps(oldMap map[string]string, newMap map[string]string) (added map[string]string, deleted []string, updated map[string]string) {
37+
added = map[string]string{}
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deleted = []string{}
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updated = map[string]string{}
40+
41+
// Compare the old map to the new
42+
for oldKey, oldValue := range oldMap {
43+
if val, ok := newMap[oldKey]; ok {
44+
// The same key exists, but the values differ - record it as updated
45+
if val != oldValue {
46+
updated[oldKey] = val
47+
}
48+
} else {
49+
// Key has been removed
50+
deleted = append(deleted, oldKey)
51+
}
52+
}
53+
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// Compare the new map to the old
55+
for newKey, newValue := range newMap {
56+
if _, ok := oldMap[newKey]; !ok {
57+
// If the key does not exist in the old map, record it as added
58+
added[newKey] = newValue
59+
}
60+
}
61+
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return added, deleted, updated
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}
64+
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func NewController(queue workqueue.RateLimitingInterface, indexer cache.Indexer, informer cache.Controller) *Controller {
66+
return &Controller{
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indexer: indexer,
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informer: informer,
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queue: queue,
70+
}
71+
}
72+
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// Calculate label changes across each node update
74+
func (c *Controller) labelUpdateHandler(key string) error {
75+
obj, exists, err := c.indexer.GetByKey(key)
76+
if err != nil {
77+
log.Error(err, "Failed to get key")
78+
return err
79+
}
80+
81+
if exists {
82+
node := obj.(*v1.Node)
83+
nodeName := node.GetName()
84+
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// Compare the cached label state to the incoming one
86+
added, deleted, updated := compareLabelMaps(nodeLabels[nodeName], node.Labels)
87+
88+
// Log any label updates
89+
if len(added) > 0 || len(deleted) > 0 || len(updated) > 0 {
90+
notification := notifiers.LabelUpdateNotification{
91+
Node: node.GetName(),
92+
Added: added,
93+
Updated: updated,
94+
Deleted: deleted,
95+
}
96+
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err := c.notifier.Notify(log, notification)
98+
if err != nil {
99+
log.Error(err, "Failed to dispatch notification")
100+
return err
101+
}
102+
}
103+
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// Remove any previously cached labels
105+
if nodeLabels[nodeName] != nil {
106+
for k := range nodeLabels[nodeName] {
107+
delete(nodeLabels[nodeName], k)
108+
}
109+
} else {
110+
// Ensure the label cache is allocated for this node
111+
nodeLabels[nodeName] = make(map[string]string)
112+
}
113+
114+
// Cache the updated label state
115+
for k, v := range node.Labels {
116+
nodeLabels[nodeName][k] = v
117+
}
118+
}
119+
120+
return nil
121+
}
122+
123+
func (c *Controller) processNextWorkItem() bool {
124+
key, quit := c.queue.Get()
125+
if quit {
126+
return false
127+
}
128+
129+
defer c.queue.Done(key)
130+
131+
err := c.labelUpdateHandler(key.(string))
132+
if err == nil {
133+
c.queue.Forget(key)
134+
return true
135+
}
136+
137+
// If we have failed, requeue the work for later
138+
c.queue.AddRateLimited(key)
139+
return true
140+
}
141+
142+
func (c *Controller) runWorker() {
143+
for c.processNextWorkItem() {
144+
}
145+
}
146+
147+
func (c *Controller) Run(threadiness int, stopCh chan struct{}) {
148+
// Let workers stop when we are done
149+
defer c.queue.ShutDown()
150+
151+
log.Info("Starting node controller")
152+
go c.informer.Run(stopCh)
153+
154+
if !cache.WaitForCacheSync(stopCh, c.informer.HasSynced) {
155+
log.Info("Timed out waiting for cache sync")
156+
return
157+
}
158+
159+
for i := 0; i < threadiness; i++ {
160+
go wait.Until(c.runWorker, time.Second, stopCh)
161+
}
162+
163+
<-stopCh
164+
log.Info("Stopping node controller")
165+
}
166+
167+
func getNodeName() (string, error) {
168+
// Within the Kubernetes Pod, the hostname provides the Pod name, rather than the node name, so we pass in the
169+
// node name via the NODE_NAME environment variable instead.
170+
nodeName := os.Getenv("NODE_NAME")
171+
if len(nodeName) > 0 {
172+
return nodeName, nil
173+
}
174+
175+
// If the NODE_NAME environment variable is unset, fall back on hostname matching (e.g. when running outside of
176+
// a Kubernetes deployment).
177+
return os.Hostname()
178+
}
179+
180+
func enqueueNodeUpdate(nodeName string, queue workqueue.RateLimitingInterface) {
181+
if nodeLocal {
182+
hostname, err := getNodeName()
183+
if err != nil {
184+
log.Error(err, "unable to determine local hostname for node-local monitoring")
185+
return
186+
}
187+
188+
if hostname != nodeName {
189+
return
190+
}
191+
}
192+
193+
queue.Add(nodeName)
194+
}
195+
196+
func main() {
197+
var endpoint string
198+
199+
flag.BoolVar(&nodeLocal, "l", false, "Only track changes to the local node")
200+
flag.StringVar(&endpoint, "n", "", "Notification endpoint to POST updates to")
201+
202+
flag.Usage = func() {
203+
fmt.Fprintf(os.Stderr, "Node Label Monitor for Kubernetes\n")
204+
fmt.Fprintf(os.Stderr, "Usage: %s [flags]\n\n", monitorName)
205+
flag.PrintDefaults()
206+
}
207+
208+
flag.Parse()
209+
210+
cfg := config.GetConfigOrDie()
211+
clientset := kubernetes.NewForConfigOrDie(cfg)
212+
213+
logf.SetLogger(zap.New(zap.UseDevMode(false)))
214+
215+
if nodeLocal {
216+
hostname, err := getNodeName()
217+
if err != nil {
218+
log.Error(err, "unable to determine local hostname for node-local monitoring")
219+
return
220+
}
221+
msg := fmt.Sprintf("configured for node-local monitoring on %s", hostname)
222+
log.Info(msg)
223+
} else {
224+
log.Info("configured for cluster-wide monitoring")
225+
}
226+
227+
// Create the node watcher
228+
nodeListWatcher := cache.NewListWatchFromClient(clientset.CoreV1().RESTClient(), "nodes", metav1.NamespaceAll, fields.Everything())
229+
230+
// Create the workqueue
231+
queue := workqueue.NewNamedRateLimitingQueue(workqueue.DefaultControllerRateLimiter(), monitorName)
232+
233+
// Monitor when nodes are added to, updated, or deleted from the Cluster
234+
indexer, informer := cache.NewIndexerInformer(nodeListWatcher, &v1.Node{}, 0, cache.ResourceEventHandlerFuncs{
235+
AddFunc: func(obj interface{}) {
236+
key, err := cache.MetaNamespaceKeyFunc(obj)
237+
if err == nil {
238+
// Add node
239+
enqueueNodeUpdate(key, queue)
240+
}
241+
},
242+
UpdateFunc: func(oldObj, newObj interface{}) {
243+
key, err := cache.MetaNamespaceKeyFunc(newObj)
244+
if err == nil {
245+
// Update node
246+
enqueueNodeUpdate(key, queue)
247+
}
248+
},
249+
DeleteFunc: func(obj interface{}) {
250+
key, err := cache.DeletionHandlingMetaNamespaceKeyFunc(obj)
251+
if err == nil {
252+
// Remove node
253+
delete(nodeLabels, key)
254+
enqueueNodeUpdate(key, queue)
255+
}
256+
},
257+
}, cache.Indexers{})
258+
259+
controller := NewController(queue, indexer, informer)
260+
261+
// Set up the notifier for this controller
262+
if len(endpoint) > 0 {
263+
var err error
264+
controller.notifier, err = notifiers.NewEndpointNotifier(log, endpoint)
265+
if err != nil {
266+
log.Error(err, "failed to instantiate endpoint notifier")
267+
return
268+
}
269+
} else {
270+
controller.notifier = notifiers.LogNotifier{}
271+
}
272+
273+
// Start the controller
274+
stop := make(chan struct{})
275+
defer close(stop)
276+
go controller.Run(1, stop)
277+
select {}
278+
}

‎notifiers/logger.go

+20
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,20 @@
1+
package notifiers
2+
3+
import (
4+
"encoding/json"
5+
"github.com/go-logr/logr"
6+
)
7+
8+
// Default log-based notifier
9+
type LogNotifier struct{}
10+
11+
func (l LogNotifier) Notify(log logr.Logger, notification LabelUpdateNotification) error {
12+
msg, err := json.Marshal(notification)
13+
if err != nil {
14+
log.Error(err, "failed to marshal JSON")
15+
return err
16+
}
17+
18+
log.Info(string(msg))
19+
return nil
20+
}

‎notifiers/notifier.go

+14
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,14 @@
1+
package notifiers
2+
3+
import "github.com/go-logr/logr"
4+
5+
type LabelUpdateNotification struct {
6+
Node string `json:"node"`
7+
Added map[string]string `json:"labelsAdded"`
8+
Deleted []string `json:"labelsDeleted"`
9+
Updated map[string]string `json:"labelsUpdated"`
10+
}
11+
12+
type LabelNotifier interface {
13+
Notify(log logr.Logger, notification LabelUpdateNotification) error
14+
}

‎notifiers/rest.go

+46
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,46 @@
1+
package notifiers
2+
3+
import (
4+
"bytes"
5+
"encoding/json"
6+
"fmt"
7+
"github.com/go-logr/logr"
8+
"net/http"
9+
"net/url"
10+
)
11+
12+
// REST Endpoint Notifier
13+
type EndpointNotifier struct {
14+
endpoint string
15+
}
16+
17+
func NewEndpointNotifier(log logr.Logger, endpoint string) (*EndpointNotifier, error) {
18+
_, err := url.ParseRequestURI(endpoint)
19+
if err != nil {
20+
log.Error(err, "failed to validate endpoint URL")
21+
return nil, err
22+
}
23+
24+
return &EndpointNotifier{
25+
endpoint: endpoint,
26+
}, nil
27+
}
28+
29+
func (e EndpointNotifier) Notify(log logr.Logger, notification LabelUpdateNotification) error {
30+
payload, err := json.Marshal(notification)
31+
if err != nil {
32+
log.Error(err, "failed to marshal JSON payload")
33+
return err
34+
}
35+
36+
msg := fmt.Sprintf("notifying %s", e.endpoint)
37+
log.Info(msg)
38+
39+
_, err = http.Post(e.endpoint, "application/json", bytes.NewBuffer(payload))
40+
if err != nil {
41+
log.Error(err, "failed to POST to endpoint")
42+
return err
43+
}
44+
45+
return nil
46+
}

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