아래의 Reference 에 있는 악분 일상 및 공식 문서를 통해 2024년 8월 14일 공식 버전 1.0.0 기준으로 재구성하여 기록하였습니다. https://aws.amazon.com/about-aws/whats-new/2024/08/karpenter-1-0/?nc1=h_ls

What is cluster autoscaler?

If you're using a cluster autoscaler, it monitors the CPU and memory required by the pods and makes resources available if they're running low to keep the pods running. Slow to create node, depend on launch template

Karpenter

Kapenter is a flexible, high-performance Kubernetes cluster autoscaler pros

• launches right-sized compute resources in response to changing application load in under a minute
• Automatically provisions new compute resources based on the specific requirements of cluster workloads

Workflow

1. NodePool and EC2NodeClass
   • NodePool: Karpenter manages multiple NodePools to cater to different workload requirements, such as Default, Wild, and Farm.
   • Each NodePool has properties like Arch, CPU, Type, AZ, and Toleration, allowing it to provision nodes that meet specific workload needs.
   • EC2NodeClass: Linked to each NodePool, EC2NodeClass holds configurations such as AMI, User Data, Security Group, Kubelet settings, and Subnet information, which guide the provisioning of EC2 instances for the nodes.
2. Monitoring Pending Pods
   • Karpenter watches for Pods in a Pending state within the cluster. If pods remain pending due to a lack of available nodes, Karpenter initiates a process to provision new nodes.
3. Creating NodeClaims
   • After detecting pending pods, Karpenter generates suitable NodeClaims. NodeClaims define the specifications of the required nodes according to the workload needs and associated conditions.
4. Requesting EC2 Instances
   • Based on the NodeClaim, Karpenter requests the necessary EC2 instance from the AWS EC2 service. This request can be for On-Demand or Spot Instances depending on the configuration. Each NodeClaim specifies the required instance type (CPU, memory, etc.), which directs this request.
5. Launching and Registering EC2 Instances
   • Once the request is accepted, the EC2 instance is launched and registered as a node according to the NodeClaim.
   • Through this process, Karpenter dynamically scales and optimizes resources within the cluster by automatically managing node provisioning based on workload demands.

For more code and explanation, see the blog below.

Karpenter Main Pages