Kubernetes Autoscaling
  • 22 May 2022
  • 3 Minutes to read
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Kubernetes Autoscaling

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Kubernetes lets you scale the pods automatically to optimize resource usage and make the backend ready according to the load in your service. Horizontal Pod Autoscaler which is a built-in component can scale your pods automatically.

Firstly, we need to have a Metrics Server to collect the metrics of the pods. To provide metric via the Metrics API, a metric server monitoring must be deployed on the cluster. Horizontal Pod Autoscaler uses this API to collect metrics.

Install Metric Server

Metric Server is usually deployed by the cloud providers. If you are using a custom Kubernetes or the Metric Server is not deployed by your cloud provider you should deploy it manually as explained below. Firstly, Check if metrics-server is installed using the command below.

kubectl get pods --all-namespaces | grep -i "metric"

You are going to see an output exactly like the below.

kube-system   metrics-server-5bb577dbd8-7f58c           1/1     Running   7          23h

Manual Installation

Download the components.yaml file on the master.


wget https://github.com/kubernetes-sigs/metrics-server/releases/latest/download/components.yaml
Add the following line to line 132 of the file. --kubelet-insecure-tls. The lines are going to seem exactly as below.
spec:
     containers:
     - args:
       - --kubelet-insecure-tls
       - --cert-dir=/tmp
       - --secure-port=4443
       - --kubelet-preferred-address-types=InternalIP,ExternalIP,Hostname
       - --kubelet-use-node-status-port
       image: k8s.gcr.io/metrics-server/metrics-server:v0.4.2

Deploy the YAML file that we have made changes.
kubectl apply -f components.yaml

Check whether everything is working properly.
kubectl get apiservices |grep "v1beta1.metrics.k8s.io"

The output of the command should be as follows.
v1beta1.metrics.k8s.io                 kube-system/metrics-server   True        21h

Create horizontal pod autoscaling

First, make a small change in our yaml file in Ant Media Server by runningkubectl edit deployment ant-media-server. Edit and save the following lines under the container according to yourself. Before proceeding let us tell you about Millicores. Millicores is a metric which is used to measure CPU usage. It is a CPU core divided into 1000 units (milli = 1000). 1000 = 1 core. So the below configuration uses 4 cores.

resources:
  requests:
  cpu: 4000m

After adding file content should be like as follows:

apiVersion: apps/v1
kind: Deployment
metadata:
  name: ant-media-server
spec:
  selector:
    matchLabels:
      run: ant-media-server
  replicas: 1
  template:
    metadata:
      labels:
        run: ant-media-server
    spec:
      hostNetwork: true
      containers:
      - name: ant-media-server
        imagePullPolicy: IfNotPresent  # change this value accordingly. It can be Never, Always or IfNotPresent
        image: ant-media-server-enterprise-k8s:test  #change this value according to your image.
        args: ["-g", "true", "-s", "true", "-r", "true", "-m", "cluster", "-h", "mongo"]
        resources:
          requests:
            cpu: 4000m

Check the accuracy of the value we entered using the command below.

kubectl describe deployment/ant-media-server

Now that the deployment is running, we're going to create a Horizontal Pod Autoscaler for it:

kubectl autoscale deployment ant-media-server --cpu-percent=60 --min=1 --max=10

or you can use the following yaml file:

kubectl create -f https://raw.githubusercontent.com/ant-media/Scripts/master/kubernetes/ams-k8s-hpa.yaml

In the above configuration, we set the CPU average as 60% and we set the pods as min 1 and maximum 10. A new pod will be created every time the CPU average passes 60%.

You can monitor the situation in the following output.

root@k8s-master:~# kubectl get hpa
NAME               REFERENCE                     TARGETS   MINPODS   MAXPODS   REPLICAS   AGE
ant-media-server   Deployment/ant-media-server   3%/60%   1         10         1          20h

New pods are going to be created when we start loading and the cpu exceeds 60%. When the cpu average value decreases below 60%, then the pods are going to be terminated.

root@k8s-master:~# kubectl get hpa
NAME               REFERENCE                     TARGETS   MINPODS   MAXPODS   REPLICAS   AGE
ant-media-server   Deployment/ant-media-server   3%/60%   1         10         1          20h

Check the number of pods running using the following command.

root@k8s-master:~# kubectl get pods
NAME                                READY   STATUS    RESTARTS   AGE
ant-media-server-7b9c6844b9-4dtwj   1/1     Running   0          42m
ant-media-server-7b9c6844b9-7b8hp   1/1     Running   0          19h
ant-media-server-7b9c6844b9-9rrwf   1/1     Running   0          18m
ant-media-server-7b9c6844b9-tdxhl   1/1     Running   0          47m
mongodb-9b99f5c-x8j5x               1/1     Running   0          20h

Utilities

The following command gives information about AutoScale:
kubectl get hpa

Check the load of pods running using the command below:
kubectl top nodes

This command prints out the following:
root@k8s-master:~# kubectl top node
NAME         CPU(cores)   CPU%   MEMORY(bytes)   MEMORY%   
k8s-node     111m         5%     717Mi           38%       
k8s-node-2   114m         5%     1265Mi          68%       
k8s-node-3   98m          4%     663Mi           35%       
k8s-node-4   102m         5%     666Mi           35%       
n8s-master   236m         11%    1091Mi          58%



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