Objective of this Operator/Controller is demonstrate
ReplicaSet kind of resource
implementation using Kubernetes controller pattern.
Another objective of this repo. is to show how to build the controller from scratch and what challenges/gotchas developer could face.
So a developer could understand the beauty KuberBuilder or Operator SDK frameworks
Once user applies the
kubectl apply -f podset.yaml) resource, controller could spin up
number of pods mentioned as per
e.g. User want to spin up 3 pod
apiVersion: demo.k8s.io/v1alpha1 kind: PodSet metadata: name: three-podset spec: replicas: 3
- Kubernetes cluster 1.9 + (minikube also works)
- golang 1.11 +
GO111MODULE="on"env if source code is in
Check out the code according to following instruction and check the README file to follow the further instructions.
git checkout step-1
covers basic code and scaffolding setup
git checkout step-2
Covers how to define CRD types, register CRD's and generate client API's using
It covers simple program that issues
watch request to
PodSet resource and print's resource state changes on console.
git checkout step-3
Covers functional controller using basic generated code. It shows how to issue watch requests and bring
PodSet resource to desired state (reconciliation).
git checkout step-4
Covers fully functional controller using shared informers, listers and workqueues. It shows how to generate all those objects. At this point one could able to relate why controllers are written in particular way.
Note: This code is intended for educational purpose. While less focus is given on code quality aspect.