kubernetes-periodic-controller

README

kubernetes-periodic-controller

An example of a periodic Kubernetes controller, bootstrapped with kubebuilder.

Description

This repo contains an example of a periodic Kubernetes controller, which reconciles objects on regular basis.

The example controller will reconcile Pods, which are annotated every 30 seconds by default.

Check out the Implementing a periodic Kubernetes controller post for more details about how this all started.

Usage

In order to quickly test the periodic controller in a local Kubernetes cluster follow these steps.

Create a local kind cluster.

kind create cluster

Start the controller. The command below will start the controller on your system.

make run

Create a sample pod to test things out.

---
apiVersion: v1
kind: Pod
metadata:
  name: busybox
  namespace: default
spec:
  containers:
  - name: busybox
    image: busybox
    command:
      - sleep
      - infinity
    imagePullPolicy: IfNotPresent
  restartPolicy: Always

Create the pod.

kubectl apply -f /path/to/sample-pod.yaml

Check that we have the pod up and running.

kubectl get pods
NAME      READY   STATUS    RESTARTS   AGE
busybox   1/1     Running   0          98s

And now, let's annotate our pod properly, so that it is considered by our controller.

kubectl annotate pod busybox dnaeon.github.io/reconcile-me=true

If you watch the controller's logs you should see similar log entries.

2024-03-23T21:28:06+02:00       INFO    reconcile       {"controller": "pod_controller", "namespace": "default", "name": "busybox", "reconcileID": "fa88e341-bb90-448e-a206-9f0cb8e52778"}
2024-03-23T21:28:36+02:00       INFO    reconcile       {"controller": "pod_controller", "namespace": "default", "name": "busybox", "reconcileID": "1676b1fd-3d0e-4f43-8542-109b0ac88fd2"}
2024-03-23T21:29:06+02:00       INFO    reconcile       {"controller": "pod_controller", "namespace": "default", "name": "busybox", "reconcileID": "a2588b69-416c-435d-bab3-06f88f26843e"}

Getting Started

Prerequisites

• Go version v1.21.0
• Docker version 17.03+
• kubectl version v1.11.3+
• Access to a Kubernetes v1.11.3+ cluster

To Deploy on the cluster

Build and push your image to the location specified by IMG:

make docker-build docker-push IMG=<some-registry>/kubernetes-periodic-controller:tag

NOTE: This image ought to be published in the personal registry you specified. And it is required to have access to pull the image from the working environment. Make sure you have the proper permission to the registry if the above commands don’t work.

Install the CRDs into the cluster:

make install

Deploy the Manager to the cluster with the image specified by IMG:

make deploy IMG=<some-registry>/kubernetes-periodic-controller:tag

NOTE: If you encounter RBAC errors, you may need to grant yourself cluster-admin privileges or be logged in as admin.

To Uninstall

Delete the APIs(CRDs) from the cluster:

make uninstall

Uninstall the controller from the cluster:

make undeploy

Project Distribution

Following are the steps to build the installer and distribute this project to users.

1. Build the installer for the image built and published in the registry:

make build-installer IMG=<some-registry>/kubernetes-periodic-controller:tag

NOTE: The makefile target mentioned above generates an 'install.yaml' file in the dist directory. This file contains all the resources built with Kustomize, which are necessary to install this project without its dependencies.

1. Using the installer

Users can just run kubectl apply -f to install the project, i.e.:

kubectl apply -f https://raw.githubusercontent.com/<org>/kubernetes-periodic-controller/<tag or branch>/dist/install.yaml

Contributing

Please contribute any suggestions and/or improvements to the Github repo.

NOTE: Run make help for more information on all potential make targets

Also, make sure to check the Kubebuilder Documentation.

License

Copyright 2024.

Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License. You may obtain a copy of the License at

http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License.