Scaling Your App

The goal of this interactive scenario is to scale a deployment with kubectl scale and to see the load balancing in action

Scaling a deployment

kubectl get deployments

NAME                  DESIRED   CURRENT   UP-TO-DATE   AVAILABLE   AGE
kubernetes-bootcamp   1         1         1            1           40m

• The DESIRED state is showing the configured number of replicas
• The CURRENT state show how many replicas are running now
• The UP-TO-DATE is the number of replicas that were updated to match the desired (configured) state
• The AVAILABLE state shows how many replicas are actually AVAILABLE to the users

kubectl scale deployments/kubernetes-bootcamp --replicas=4

deployment.extensions "kubernetes-bootcamp" scaled

kubectl get deployments

NAME                  DESIRED   CURRENT   UP-TO-DATE   AVAILABLE   AGE
kubernetes-bootcamp   4         4         4            4           41m

The change was applied, and we have 4 instances of the application available

kubectl get pods -o wide

NAME                                   READY     STATUS    RESTARTS   AGE       IP           NODE
kubernetes-bootcamp-5c69669756-f7dnz   1/1       Running   0          35s       172.17.0.6   minikube
kubernetes-bootcamp-5c69669756-hrcqx   1/1       Running   0          35s       172.17.0.5   minikube
kubernetes-bootcamp-5c69669756-jbdr4   1/1       Running   0          35s       172.17.0.7   minikube
kubernetes-bootcamp-5c69669756-vdwgm   1/1       Running   0          41m       172.17.0.4   minikube

There are 4 Pods now, with different IP addresses

To check that the change was registered in the Deployment events log

kubectl describe deployments/kubernetes-bootcamp

Name:                   kubernetes-bootcamp
Namespace:              default
CreationTimestamp:      Sun, 10 Jun 2018 15:08:14 +0000
Labels:                 run=kubernetes-bootcamp
Annotations:            deployment.kubernetes.io/revision=1
Selector:               run=kubernetes-bootcamp
Replicas:               4 desired | 4 updated | 4 total | 4 available | 0 unavailable
StrategyType:           RollingUpdate
MinReadySeconds:        0
RollingUpdateStrategy:  1 max unavailable, 1 max surge
Pod Template:
  Labels:  run=kubernetes-bootcamp
  Containers:
   kubernetes-bootcamp:
    Image:        gcr.io/google-samples/kubernetes-bootcamp:v1
    Port:         8080/TCP
    Host Port:    0/TCP
    Environment:  <none>
    Mounts:       <none>
  Volumes:        <none>
Conditions:
  Type           Status  Reason
  ----           ------  ------
  Progressing    True    NewReplicaSetAvailable
  Available      True    MinimumReplicasAvailable
OldReplicaSets:  <none>
NewReplicaSet:   kubernetes-bootcamp-5c69669756 (4/4 replicas created)
Events:
  Type    Reason             Age   From                   Message
  ----    ------             ----  ----                   -------
  Normal  ScalingReplicaSet  42m   deployment-controller  Scaled up replica set kubernetes-bootcamp-5c69669756 to 1
  Normal  ScalingReplicaSet  57s   deployment-controller  Scaled up replica set kubernetes-bootcamp-5c69669756 to 4

Load Balancing

kubectl expose deployment/kubernetes-bootcamp --type="NodePort" --port 8080
service "kubernetes-bootcamp" exposed

kubectl describe services/kubernetes-bootcamp

Name:                     kubernetes-bootcamp
Namespace:                default
Labels:                   run=kubernetes-bootcamp
Annotations:              <none>
Selector:                 run=kubernetes-bootcamp
Type:                     NodePort
IP:                       10.101.238.220
Port:                     <unset>  8080/TCP
TargetPort:               8080/TCP
NodePort:                 <unset>  31431/TCP
Endpoints:                172.17.0.4:8080,172.17.0.5:8080,172.17.0.6:8080 + 1 more...
Session Affinity:         None
External Traffic Policy:  Cluster
Events:                   <none>

export NODE_PORT=$(kubectl get services/kubernetes-bootcamp -o go-template='{{(index .spec.ports 0).nodePort}}')

echo NODE_PORT=$NODE_PORT
NODE_PORT=31431

We’ll do a curl to the exposed IP and port. Execute the command multiple times

curl $(minikube ip):$NODE_PORT
Hello Kubernetes bootcamp! | Running on: kubernetes-bootcamp-5c69669756-hrcqx | v=1

curl $(minikube ip):$NODE_PORT
Hello Kubernetes bootcamp! | Running on: kubernetes-bootcamp-5c69669756-jbdr4 | v=1

curl $(minikube ip):$NODE_PORT
Hello Kubernetes bootcamp! | Running on: kubernetes-bootcamp-5c69669756-vdwgm | v=1

curl $(minikube ip):$NODE_PORT
Hello Kubernetes bootcamp! | Running on: kubernetes-bootcamp-5c69669756-f7dnz | v=1

We hit a different Pod with every request. This demonstrates that the load-balancing is working

Scale Down

kubectl scale deployments/kubernetes-bootcamp --replicas=2

deployment.extensions "kubernetes-bootcamp" scaled

kubectl get deployments

NAME                  DESIRED   CURRENT   UP-TO-DATE   AVAILABLE   AGE
kubernetes-bootcamp   2         2         2            2           59m

kubectl get pods -o wide
NAME                                   READY     STATUS        RESTARTS   AGE       IP           NODE
kubernetes-bootcamp-5c69669756-f7dnz   1/1       Terminating   0          18m       172.17.0.6   minikube
kubernetes-bootcamp-5c69669756-hrcqx   1/1       Terminating   0          18m       172.17.0.5   minikube
kubernetes-bootcamp-5c69669756-jbdr4   1/1       Running       0          18m       172.17.0.7   minikube
kubernetes-bootcamp-5c69669756-vdwgm   1/1       Running       0          59m       172.17.0.4   minikube

kubectl get pods -o wide
NAME                                   READY     STATUS    RESTARTS   AGE       IP           NODE
kubernetes-bootcamp-5c69669756-jbdr4   1/1       Running   0          18m       172.17.0.7   minikube
kubernetes-bootcamp-5c69669756-vdwgm   1/1       Running   0          1h        172.17.0.4   minikube

This confirms that 2 Pods were terminated.