Kubernetes Autoscaling

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 Metrics 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

• Make a small change in our yaml file in Ant Media Server. kubectl edit deployment ant-media-server. Edit and save the following lines under the container according to yourself. Before proceeding let us tell 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.
  

You basically need to update the mongodb server url(-h) below. You may also need to add -u and -p parameters for

specifying mongodb username and passwords respectively

      args: ["-g", "true", "-s", "true", "-r", "true", "-m", "cluster", "-h", "127.0.0.1"]
      resources:
        requests:
          cpu: 1000m

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. 

* Create Horizontal Pod AutoScaling

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 52%/60% 1 10 4 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

* Following command gives information about AutoScale.

kubectl get hpa

* Check the load of pods running using the command below.

kubectl top nodes

prints out something below

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%