Seika - 星歌

Kubernetes Custom Resource maintains quantity of Pods in each Node

1. Introduction

Seika is a Kubernetes Custom Resource maintains quantity of Pods in each Node without creating many ReplicaSet or Deployment.

The name Seika is inspired by the character Ijichi Seika from the anime Bocchi the rock.

For use purpose only, all you need is in dist/

Seika is trusted and being deployed in the ikukantai Fleet

2. Install

Install CRD to your Kubernetes System

$ kubectl apply -f dist/install.yaml

3. How to use

Take a quick view in dist/seika-sample.yaml

apiVersion: batch.bonavadeur.io/v1
kind: Seika
metadata:
  labels:
    app.kubernetes.io/name: seika
    app.kubernetes.io/instance: seika-sample
    app.kubernetes.io/part-of: seika
    app.kubernetes.io/managed-by: kustomize
    app.kubernetes.io/created-by: seika
  name: seika-sample
spec:
  repurika:
    node1: 1
    node2: 2
    node3: 3
  selector:
    matchLabels:
      bonavadeur.io/seika: seika-sample
  template:
    spec:
      containers:
      - name: shuka
        image: docker.io/bonavadeur/shuka:sleep

Note:

• Pod's labels is not required. Pods are labeled with Seika's Labels. In the yaml file above, Pods are labels with bonavadeur.io/seika: seika-sample
• .spec.repurika field specify quantity of Pods in each node, with key is nodename and value is an integer specify desired number of Pods in that node

Let's apply a Seika Instance

$ kubectl apply -f dist/seika-sample.yaml
$ kubectl get pod | grep seika
seika-sample-node1-u8knc       1/1     Running   0               15m    10.233.102.166   node1   <none>           <none>
seika-sample-node2-cgo5g       1/1     Running   0               16m    10.233.75.25     node2   <none>           <none>
seika-sample-node2-qkp5u       1/1     Running   0               16m    10.233.75.47     node2   <none>           <none>
seika-sample-node3-7qf9g       1/1     Running   0               8s     10.233.71.45     node3   <none>           <none>
seika-sample-node3-efl0y       1/1     Running   0               9s     10.233.71.49     node3   <none>           <none>
seika-sample-node3-q8i96       1/1     Running   0               16m    10.233.71.43     node3   <none>           <none>
$ kubectl get seika
NAME           NODES                       READY
seika-sample   ["node1","node2","node3"]   1-2-3/1-2-3

4. For Development

4.1. Build and Run commands

# install CRD to Kubernetes
$ make install
$ make uninstall
# run Seika controller locally
$ make run
# build Docker image and push to DockerHub
$ make docker-build docker-push IMG=docker.io/bonavadeur/seika:v1.2
# deploy and undeploy
$ make deploy IMG=docker.io/bonavadeur/seika:v1.2
$ make undeploy
# regenerate manifest whenever you make a change to api/v1/seika_types.go
$ make generate IMG=docker.io/bonavadeur/seika:v1.2
$ make manifests IMG=docker.io/bonavadeur/seika:v1.2
# build install.yaml file
$ make build-installer IMG=docker.io/bonavadeur/seika:v1.2

4.2. Edit Seika using kubectl patch

$ kubectl patch seika seika-sample --type=merge --patch '{"spec":{"repurika":{"node1":1,"node2":2,"node3":1}}}'

4.3. Edit Seika using client-go library

import (
  "encoding/json"
  "fmt"
  "context"

  "k8s.io/apimachinery/pkg/runtime/schema"
  metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
  "k8s.io/apimachinery/pkg/types"
  "k8s.io/apimachinery/pkg/apis/meta/v1/unstructured"
)

func patchSeika(desiredPods map[string]int32) {
	gvr := schema.GroupVersionResource{
		Group:    "batch.bonavadeur.io",
		Version:  "v1",
		Resource: "seikas",
	}

	// Define the patch data
	repurika := map[string]interface{}{}
	for _, nodename := range NODENAMES {
		repurika[nodename] = desiredPods[nodename]
	}
	patchData := map[string]interface{}{
		"spec": map[string]interface{}{
			"repurika": repurika,
		},
	}

	// Convert patch data to JSON
	patchBytes, err := json.Marshal(patchData)
	if err != nil {
		fmt.Printf("Error marshalling patch data: %v", err)
	}

	// Namespace and resource name
	namespace := "default"
	resourceName := "seika-sample"

	// Execute the patch request
	patchedResource, err := DYNCLIENT.Resource(gvr).
		Namespace(namespace).
		Patch(context.TODO(), resourceName, types.MergePatchType, patchBytes, metav1.PatchOptions{})
	if err != nil {
		fmt.Errorf("Error patching resource: ", err)
	} else {
		resource, found, _ := unstructured.NestedString(patchedResource.Object, "metadata", "name")
		if !found {
			fmt.Errorf("Seika not found:", err)
		}
		fmt.Println("Patched resource:", resource)
	}
}

5. Contributeur

Đào Hiệp - Bonavadeur - ボナちゃん
The Future Internet Laboratory, Room E711 C7 Building, Hanoi University of Science and Technology, Vietnam.
未来のインターネット研究室, C7 の E ７１１、ハノイ百科大学、ベトナム。