Introduction to Node Autoscaling in Kubernetes

Node autoscaling in Kubernetes is a powerful feature that adjusts the number of nodes in a cluster to align with fluctuating workloads. By enabling node autoscaling, we allow the system to allocate resources dynamically, scaling up during traffic peaks and down during idle times. On AWS Elastic Kubernetes Service (EKS), node autoscaling integrates seamlessly with Cluster Autoscaler, creating resilient, cost-effective clusters capable of handling diverse workloads efficiently.

Understanding the Need for Node Autoscaling

Node autoscaling is essential in cloud environments, especially for applications with varying demand levels. Kubernetes clusters can quickly become costly if nodes run continuously at low utilization, making autoscaling necessary for:

  • Cost Optimization: Dynamically adjusts resources based on need, reducing costs by terminating idle nodes.
  • Improved Application Resilience: Ensures the cluster can handle unexpected spikes in demand by scaling up nodes.
  • Efficient Resource Utilization: Optimizes usage across nodes, keeping workloads balanced.

Setting Up the Environment: AWS EKS and Tools

To get started with implementing node autoscaling, we’ll need to prepare our environment:

  1. AWS CLI: For managing AWS resources and EKS clusters.
  2. kubectl: The Kubernetes command-line tool to manage and deploy resources on the EKS cluster.
  3. eksctl: Simplifies EKS cluster creation and management, including node group setup.

Ensure AWS CLI, kubectl, and eksctl are installed and configured with the necessary IAM permissions.

Creating the EKS Cluster and Deploying the Metrics Server

  1. Create the EKS Cluster: Use eksctl to create the EKS cluster, specifying node group configurations that allow scaling.
    eksctl create cluster –name my-eks-cluster –nodes-min=1 –nodes-max=5 –region us-west-2
  2. Deploy the Metrics Server: Node autoscaling requires the Kubernetes Metrics Server to monitor resource usage.
    kubectl apply -f https://github.com/kubernetes-sigs/metrics-server/releases/latest/download/components.yaml

Verify the Metrics Server is running by checking its pods:
kubectl get pods -n kube-system | grep metrics-server

Configuring IAM Roles for Cluster Autoscaler

Cluster Autoscaler needs permission to add or remove nodes. Configure IAM roles to grant this access:

  1. Create IAM Role for Cluster Autoscaler: Use the AWS Management Console or AWS CLI to create an IAM role with policies that allow autoscaling activities.
  2. Attach the IAM Role to the EKS Cluster: Assign the role to the EKS worker nodes, ensuring the Cluster Autoscaler has sufficient permissions.

Deploying the Cluster Autoscaler Component

  1. Install Cluster Autoscaler: Use kubectl to deploy Cluster Autoscaler from the Kubernetes official repository.
    kubectl apply -f https://github.com/kubernetes/autoscaler/releases/latest/download/cluster-autoscaler.yaml
  2. Configure Cluster Autoscaler: Edit the Cluster Autoscaler deployment file to add the appropriate IAM role and ensure it only operates within the defined node group size limits.
  3. Set Autoscaler Parameters: Specify parameters to manage node scaling behavior, such as –balance-similar-node-groups for balancing and –skip-nodes-with-system-pods for skipping nodes with essential pods.

Testing Node Autoscaling with Workload Simulation

To verify the setup, simulate a workload that triggers node autoscaling:

  1. Deploy a Sample Workload: Create a deployment with high resource requests to exceed the current node capacity, prompting the Cluster Autoscaler to scale up.
    kubectl run stress-test –image=busybox –replicas=5 –command — /bin/sh -c “while true; do echo ‘load’; sleep 30; done”
  2. Monitor the Autoscaler Logs: Observe the Cluster Autoscaler’s behavior by checking its logs for node provisioning activities.
    kubectl -n kube-system logs -f deployment/cluster-autoscaler

Observing the Effects of Load on Node and Pod Scheduling

Use kubectl commands and AWS EKS monitoring tools to view how nodes and pods adjust to workload demands:

  • Check Pod Distribution: Monitor pod placement across nodes to ensure balanced distribution.
  • Inspect Node Status: Confirm that new nodes are added when the workload increases.

Scaling Down: Termination of Unnecessary Nodes

Once the workload reduces, Cluster Autoscaler will begin scaling down nodes:

  1. Stop or Scale Down the Test Workload:
    kubectl delete deployment stress-test
  2. Observe Node Termination: Verify that nodes are removed as demand decreases, ensuring cost efficiency.
    kubectl get nodes

Conclusion: Enhancing Scalability and Efficiency in Kubernetes Clusters

Node autoscaling in AWS EKS is a vital capability for dynamic environments, enabling applications to scale in response to demand while controlling costs. Following this guide, you can confidently implement and configure node autoscaling, ensuring that your Kubernetes clusters on AWS EKS are optimized for high efficiency, resilience, and performance.

References

Scale cluster compute with Karpenter and Cluster Autoscaler

Cluster Autoscaler