Scale-out and scale-in of Kubernetes cluster

In this task we will see how to scale-out and scale-in of Kubernetes cluster.

  • go to Cloud page, choose Kubernetes and open your cluster:

  • In opening cluster choose Resize

  • Choose how many nodes you need and use action resize cluster

  • Wait until update progress will end:


Let’s see how it works on server side:

  • Create Kubernetes cluster with existing parametrs (How to create Kubernetes cluster you can see in this core task Kubernetes cluster:
Master count: 1
Node count: 1
Docker volume size (Gb): 30
Node flavor: VC-2
Master node flavor: VC-2

apiVersion: apps/v1
kind: Deployment
metadata:
  name: deployment-test
  labels:
    app: nginx
spec:
  replicas: 5
  selector:
    matchLabels:
      app: nginx
  template:
    metadata:
      labels:
        app: nginx
    spec:
      containers:
      - name: nginx
        image: nginx:1.7.9
        resources:
          requests:
            memory: "400Mi"
        ports:
        - containerPort: 80
  • Create deployment using next command to create deployment. 
    kubectl apply -f deployment-test.yaml

    deployment.apps/deployment-test created
  • Using command kubectl get pods we will see that one of pods can’t move in running state: 
    kubectl get pods

    NAME                               READY   STATUS      RESTARTS   AGE
deployment-test-8676b58c7f-6hfl6   1/1     Running     0          61s
deployment-test-8676b58c7f-bk72m   1/1     Running     0          61s
deployment-test-8676b58c7f-pnwk4   0/1     Pending     0          61s
deployment-test-8676b58c7f-vnkwc   1/1     Running     0          61s
deployment-test-8676b58c7f-xlkhv   1/1     Running     0          61s
  • Using command kubectl describe pod "pod name" we will see that this pod have problem: Insufficient memory 
    kubectl describe pod deployment-test-8676b58c7f-pnwk4

    Status:         Pending
IP:
Controlled By:  ReplicaSet/deployment-test-8676b58c7f
Containers:
nginx:
  Image:      nginx:1.7.9
  Port:       80/TCP
  Host Port:  0/TCP
  Requests:
    memory:     400Mi
  Environment:  <none>
  Mounts:
    /var/run/secrets/kubernetes.io/serviceaccount from default-token-vzppl (ro)
Conditions:
Type           Status
PodScheduled   False
Volumes:
default-token-vzppl:
  Type:        Secret (a volume populated by a Secret)
  SecretName:  default-token-vzppl
  Optional:    false
QoS Class:       Burstable
Node-Selectors:  <none>
Tolerations:     node.kubernetes.io/not-ready:NoExecute for 300s
               node.kubernetes.io/unreachable:NoExecute for 300s
Events:
Type     Reason            Age                 From               Message
----     ------            ----                ----               -------
Warning  FailedScheduling  74s (x4 over 4m5s)  default-scheduler  0/2 nodes are available: 1 Insufficient memory, 1 node(s) had taints that the pod didn't tolerate.

  • Now resize cluster and add one more node like we saw on steps earlier.

  • Use the command kubectl get nods to make sure that one more node was added: 
    kubectl get nods

    NAME                                 STATUS   ROLES    AGE     VERSION
cluster-test-yin3p44gdbom-master-0   Ready    master   93m     v1.17.3
cluster-test-yin3p44gdbom-node-0     Ready    <none>   91m     v1.17.3
cluster-test-yin3p44gdbom-node-1     Ready    <none>   4m14s   v1.17.3
  • Use comand kubectl get pods and make sure that all pods in running state: 
    kubectl get pods

    NAME                               READY   STATUS      RESTARTS   AGE
deployment-test-8676b58c7f-6hfl6   1/1     Running     0          61s
deployment-test-8676b58c7f-bk72m   1/1     Running     0          61s
deployment-test-8676b58c7f-pnwk4   1/1     Running     0          61s
deployment-test-8676b58c7f-vnkwc   1/1     Running     0          61s
deployment-test-8676b58c7f-xlkhv   1/1     Running     0          61s