Writing a Kubernetes operator from scratch

In this article, we'll take a closer look at how to create your own Kubernetes operator from scratch. Operators are plug-ins that use custom resources (kind) to manage applications. Read the official documentation for details .

— HelloApp. HelloApp, Kubernetes.

kind: HelloApp — (Custom Resource Definition, CRD), ( ). ( ).

, , Go. .

() , Kubernetes API.

Kubernetes:

Kubernetes — . API ( API). , , API Kubernetes . . . Go — Kubernetes, , .

:

1. Go lang (1.16)
2. Operator SDK (1.5)
3. Kind
4. Visual Studio Code Go

:

1:

2:

3: CRD

4: CRD

5:

6:

7:

1:

, Operator SDK. Operator SDK 1.5. SDK, . .

$ mkdir demo-operator
$ cd demo-operator
$ operator-sdk init --domain anupam.com --repo 
github.com/anupamgogoi/demo-operator
      
      

        
        
        
      

    
        
        
        
      
      

        
        
        
      

    
    

API

$ operator-sdk create api --group apps --version v1 --kind HelloApp --resource --controller
      
      

        
        
        
      

    
        
        
        
      
      

        
        
        
      

    
    

.

:

1. Makefile , , . make help, .
2. . , .
3. . .
4. .
5. , . .

2:

. CRD (), () kind HelloApp , spec.size.

. spec : image () size (). spec, [4] .

. . — HelloApp , . , spec.size, — . . API .

Reconciler, Reconcile. Reconcile , CRUD (create read update delete — « », . ), (kind) (spec). , .

main.go

main.go Operator-SDK . , . main.go.

main.go:

ctrl.GetConfigOrDie() Kubernetes ~/.kube/config . ~/.kube/config :

IP , . . . GetConfigOrDie() , ctrl.NewManager() . API API Kubernetes. . main.go, .

kubectl CLI API API Kubernetes. :

$ kubectl get nodes --v=8
      
      

        
        
        
      

    
        
        
        
      
      

        
        
        
      

    
    

3: CRD

, HelloApp . CRD. demo-operator :

$ make manifests
      
      

        
        
        
      

    
        
        
        
      
      

        
        
        
      

    
    

CRD

~/demo-operator/config/crd/bases

~/demo-operator/config/samples .

4: CRD

, . kind, .

$ kind create cluster --name k8s
      
      

        
        
        
      

    
        
        
        
      
      

        
        
        
      

    
    

CRD :

$ make install
      
      

        
        
        
      

    
        
        
        
      
      

        
        
        
      

    
    

~/demo-operator/config/crd/bases

$ kubectl apply -f .
      
      

        
        
        
      

    
        
        
        
      
      

        
        
        
      

    
    

.

5:

. Kubernetes,

$ cd demo-operator
$ go run main.go
      
      

        
        
        
      

    
        
        
        
      
      

        
        
        
      

    
    

:

— samples :

$ kubectl create ns test
$ kubectl apply -f apps_v1_helloapp.yaml -n test
      
      

        
        
        
      

    
        
        
        
      
      

        
        
        
      

    
    

, test:

$ kubectl get all -n test
      
      

        
        
        
      

    
        
        
        
      
      

        
        
        
      

    
    

:

$ kubectl get HelloApp -n test
      
      

        
        
        
      

    
        
        
        
      
      

        
        
        
      

    
    

— !

6:

— , .

, -, CRD , 4 ( CRD).

, k8s . Go Visual Studio Code . Run → Start Debugging VS Code, .

— :

, ~/demo-operator/config/samples

CRD.

$ kubectl apply -f apps_v1_helloapp.yaml -n test
      
      

        
        
        
      

    
        
        
        
      
      

        
        
        
      

    
    

Reconcile, Reconcile, . Reconcile. , , .

7:

— (YAML) docker- . :

1. .
2. .
3. , API Kubernetes.
4. 2.
5. , .

~/demo-operator/config/rbac . . ?

.

:

1. Get, HelloApp. , Get HelloApp, API apps.anupam.com.
2. Get, Deployment. , Deployment Kubernetes API apps.
3. Update Deployment, API apps.

, +.

//+kubebuilder:rbac:groups=apps.anupam.com,resources=helloapps,verbs=get;list;watch;create;update;patch;delete
//+kubebuilder:rbac:groups=apps,resources=deployments,verbs=get;list;watch;create;update;patch;delete
//+kubebuilder:rbac:groups=apps.anupam.com,resources=helloapps/status,verbs=get;update;patch
//+kubebuilder:rbac:groups=apps.anupam.com,resources=helloapps/finalizers,verbs=update
      
      

        
        
        
      

    
        
        
        
      
      

        
        
        
      

    
    

. Kubernetes . controller-gen CLI (CRD, RBAC . .).

make manifests. , , — CRD, , . .

Docker-

— docker- Kubernetes.

, Dockerfile, Operator-SDK. .

docker-:

$ make docker-build IMG=anupamgogoi/demo-operator:latest
      
      

        
        
        
      

    
        
        
        
      
      

        
        
        
      

    
    

docker. registry :

make docker-push IMG=anupamgogoi/demo-operator:latest
      
      

        
        
        
      

    
        
        
        
      
      

        
        
        
      

    
    

.

dist 5 , .

1-Namespace.yaml ( ). . 2, 3 4 rbac. 5 crd/bases. , 6-Controller.yaml, . . .

.

Kubernetes CentOS. . . - Kubernetes . .

dist - , kubectl apply .

demo-operator-system. , .

. CRD. CRD — helloapps.apps.anupam.com, 5-apps.anupam.com_helloapps.yaml.

, kind, HelloApp. - , HelloApp.

, HelloApp ( ) . Kubernetes.

, HelloApp.

$ kubectl get all -n test
      
      

        
        
        
      

    
        
        
        
      
      

        
        
        
      

    
    

!

, (size=1).

, IP .

. .

Kubernetes Operator-SDK. Go, . !