Guestbook Operator with Operator SDK.

This is hobby project which creates k8s operator for guestbook application.

I will update this repo step by step and tag it from 00. I will try to explain how to reach this status. Master branch has everything in it.

tag stage_00: initialize empty operator project

• Here is my env details versions (links to install guide)

  • GO: 1.14
  • operator sdk: v0.16.0
  • Git : 2.15.0
  • docker : 19.03.5,
  • kubectl: 1.17

• To create this operator I am following this guide.

• As a first step ran the command

  operator-sdk new guestbook --repo=github.com/gurunath/guestbook

  I given --repo option as I am not using default go path to keep my go code.

• This will generate basic scaffolding for our operator. I will not go in detail, many other blogs explained it very nicely.

tag stage_01: create new CRD

• To create ne CRD, run the command in created directory

  operator-sdk add api --api-version=gurunath/v1alpha1 --kind=Guestbook

  This will scaffold the Guestbook resource API under /pkg/apis/gurunath/v1alpha1/

• Define the specs and status:

  • in first round, we will just create deployments if not present. for this we need to get redis slave image, redis master image and guestbook image

  • add these properties in guestbook_types.go file.

    • GuestbookSpec

      RedisSlave  string `json:"redisSlave"`
      RedisMaster string `json:"redisMaster"`
      GuestBook   string `json:"guestBook"`
      

      we will add validations in next steps
    • GuestbookStatus

      RedisSlavePods  []string `json:"redisSlavesPods"`
      RedisMasterPods []string `json:"redisMasterPods"`
      GuestBookPods   []string `json:"guestBookPods"`
      

  • for simplicity not added any validations till now

  • After updating file always run the following command to update the generated code for that resource type

    operator-sdk generate k8s

  • now Update / generate CRD file operator-sdk generate crds

  • in next steps we will write our controller.

• Add new Controller

  • Add a new Controller to the project that will watch and reconcile the Guestbook resource with bellow command

    operator-sdk add controller --api-version=gurunath/v1alpha1 --kind=Guestbook

    This will scaffold a new Controller implementation under pkg/controller/guestbook

  • comments are added in the controller please go through the file.

• Deployment

  • generate docker image for the operator with command operator-sdk build gurunath/guestbook-operator:0.0.1 where gurunath/guestbook-operator is public docker repo and 0.0.1 is the tag
  • after docker image build push the image to repo.
  • create deployment, role, role binding and service account for the operator. Operator-sdk provide manifests files in deploy directory

• Demo

  • Deployed this operator as Katakoda scenario please take a look.