---
title: "Scale a Cluster with CA"
date: 2018-08-07T08:30:11-07:00
weight: 40
---

## Deploy a Sample App

We will deploy an sample nginx application as a `ReplicaSet` of 1 `Pod`

```bash
cat <<EoF> ~/environment/cluster-autoscaler/nginx.yaml
apiVersion: apps/v1
kind: Deployment
metadata:
  name: nginx-to-scaleout
spec:
  replicas: 1
  selector:
    matchLabels:
      app: nginx
  template:
    metadata:
      labels:
        service: nginx
        app: nginx
    spec:
      containers:
      - image: nginx
        name: nginx-to-scaleout
        resources:
          limits:
            cpu: 500m
            memory: 512Mi
          requests:
            cpu: 500m
            memory: 512Mi
EoF

kubectl apply -f ~/environment/cluster-autoscaler/nginx.yaml

kubectl get deployment/nginx-to-scaleout
```

## Scale our ReplicaSet

Let's scale out the replicaset to 10

```bash
kubectl scale --replicas=10 deployment/nginx-to-scaleout
```

Some pods will be in the `Pending` state, which triggers the cluster-autoscaler to scale out the EC2 fleet.

```bash
kubectl get pods -l app=nginx -o wide --watch
```

{{< output >}}
NAME                                 READY     STATUS    RESTARTS   AGE

nginx-to-scaleout-7cb554c7d5-2d4gp   0/1       Pending   0          11s
nginx-to-scaleout-7cb554c7d5-2nh69   0/1       Pending   0          12s
nginx-to-scaleout-7cb554c7d5-45mqz   0/1       Pending   0          12s
nginx-to-scaleout-7cb554c7d5-4qvzl   0/1       Pending   0          12s
nginx-to-scaleout-7cb554c7d5-5jddd   1/1       Running   0          34s
nginx-to-scaleout-7cb554c7d5-5sx4h   0/1       Pending   0          12s
nginx-to-scaleout-7cb554c7d5-5xbjp   0/1       Pending   0          11s
nginx-to-scaleout-7cb554c7d5-6l84p   0/1       Pending   0          11s
nginx-to-scaleout-7cb554c7d5-7vp7l   0/1       Pending   0          12s
nginx-to-scaleout-7cb554c7d5-86pr6   0/1       Pending   0          12s
nginx-to-scaleout-7cb554c7d5-88ttw   0/1       Pending   0          12s
{{< /output >}}

View the cluster-autoscaler logs

```bash
kubectl -n kube-system logs -f deployment/cluster-autoscaler
```

You will notice Cluster Autoscaler events similar to below
![CA Scale Up events](/images/scaling-asg-up2.png)

Check the [EC2 AWS Management Console](https://console.aws.amazon.com/ec2/home?#Instances:sort=instanceId) to confirm that the Auto Scaling groups are scaling up to meet demand. This may take a few minutes. You can also follow along with the pod deployment from the command line. You should see the pods transition from pending to running as nodes are scaled up.

![Scale Up](/images/scaling-asg-up.png)

or by using the kubectl

```bash
kubectl get nodes
```

Output

{{< output >}}
ip-192-168-12-114.us-east-2.compute.internal   Ready    <none>   3d6h   v1.17.7-eks-bffbac
ip-192-168-29-155.us-east-2.compute.internal   Ready    <none>   63s    v1.17.7-eks-bffbac
ip-192-168-55-187.us-east-2.compute.internal   Ready    <none>   3d6h   v1.17.7-eks-bffbac
ip-192-168-82-113.us-east-2.compute.internal   Ready    <none>   8h     v1.17.7-eks-bffbac
{{< /output >}}