K8S Cluster Autoscaler Module
This Terraform Module installs a Cluster Autoscaler to automatically scale up and down the nodes in a cluster in response to resource utilization.
This module is responsible for manipulating each Auto Scaling Group (ASG) that was created by the EKS cluster workers module. By default, the ASG is configured to allow zero-downtime deployments but is not configured to scale automatically. You must launch an EKS control plane with worker nodes for this module to function.
Important Considerations
- The autoscaler doesn't account for CPU or Memory usage in deciding to scale up, it scales up when Pods fail to schedule due to insufficient resources. This means it's important to carefully the manage the compute resources you assign to your deployments. See the Kubernetes documentation on compute resources for more information.
- Scaling down happens when utilization dips below a specified threshold and there are pods that are able to be moved to another node. There are a variety of conditions to be aware of that can prevent pods from being automatically removable which can result in wasted capacity.
How do I deploy the Pods to Fargate?
To deploy the Pods to Fargate, you can use the create_fargate_profile variable to true and specify the subnet IDs
for Fargate using vpc_worker_subnet_ids. Note that if you are using Fargate, you must rely on the IAM Roles for
Service Accounts (IRSA) feature to grant the necessary AWS IAM permissions to the Pod. This is configured using the
use_iam_role_for_service_accounts, eks_openid_connect_provider_arn, and eks_openid_connect_provider_url input
variables.