Operator-101

A Kubernetes Operator tutorial based on Kubebuilder.

It will take you building to a full-featured cronjob controller step by step:

Installation

There are some prerequisites that need to be installed in advance.

Go

Extract the archive we downloaded into /usr/local, creating a Go tree in /usr/local/go:

$ rm -rf /usr/local/go && tar -C /usr/local -xzf go1.15.9.linux-amd64.tar.gz

Add /usr/local/go/bin to the PATH environment variable in /etc/profile:

$ export PATH=$PATH:/usr/local/go/bin
$ export PATH=$PATH:$HOME/go/bin
$ export GO111MODULE=on

Verify that Go has installed successfully:

$ go version

go version go1.15.9 linux/amd64

Docker

Install the docker package:

$ sudo zypper install docker

To automatically start the Docker service at boot time:

$ sudo systemctl enable docker.service

Start the Docker service:

$ sudo systemctl start docker.service

To allow a certain user to connect to the local Docker daemon, use the following command:

$ sudo /usr/sbin/usermod -aG docker i516697

minikube

Download and install the latest minikube:

$ curl -LO https://storage.googleapis.com/minikube/releases/latest/minikube-linux-amd64
$ sudo install minikube-linux-amd64 /usr/local/bin/minikube

Start our cluster:

$ minikube start --driver=docker --kubernetes-version=v1.17.0

Create a symbolic link to minikube's binary named kubectl:

$ ln -s $(which minikube) /usr/local/bin/kubectl

kustomize

The following script detects our OS and downloads the appropriate kustomize binary to our current working directory:

$ curl -s "https://raw.githubusercontent.com/kubernetes-sigs/kustomize/master/hack/install_kustomize.sh" | bash

controller-gen

This will install controller-gen binary in GOPATH/bin:

$ go get sigs.k8s.io/controller-tools/cmd/controller-gen@v0.2.5

Kubebuilder

Download kubebuilder and install locally:

$ os=$(go env GOOS)
$ arch=$(go env GOARCH)
$ curl -L https://go.kubebuilder.io/dl/2.3.2/${os}/${arch} | tar -xz -C /tmp/
$ sudo mv /tmp/kubebuilder_2.3.2_${os}_${arch}/* /usr/local/kubebuilder
$ export PATH=$PATH:/usr/local/kubebuilder/bin

Usage

It covers initialization, development, deployment and testing.

Initialization

1. Tell Go and kubebuilder the base import path of our module:

   $ go mod init github.com/umarelx/Operator-101
   

2. Scaffold out a new project:

   $ kubebuilder init --domain github.com
   

3. Add a new API:

   $ kubebuilder create api --group batch --version v1 --kind CronJob
   

Development

1. Design CronJob API;
2. Implement CronJob Controller;

Deployment

1. Install CRDs and run the controller locally:

   $ make install
   $ make run
   

2. Install instances of CRs:

   $ kubectl apply -f config/samples/batch_v1_cronjob.yaml
   

3. Build/Push our image and deploy the controller to cluster:

   $ make docker-build docker-push IMG=umarelx/cronjob:latest
   $ make deploy IMG=umarelx/cronjob:latest
   

Testing

1. Setup Test Environment;
2. Test Controller's Behavior;

Miscellaneous

Execute integration tests and compile:

$ make test
$ make

Check cronjob's running/updating status:

$ kubectl get cronjob.batch.github.com cronjob-sample -o yaml
$ kubectl get job

Delete instances of CRs:

$ kubectl delete cronjob.batch.github.com cronjob-sample

Check/Delete namespace after deployment:

$ kubectl get namespace
$ kubectl delete namespace operator-101-system

Delete CRDs from a cluster:

$ make uninstall

Contributing

We love contributions! Before submitting a Pull Request, it's always good to start with a new issue first.

License

This repository is licensed under Apache 2.0. Full license text is available in LICENSE.