Deploy The Spot Interrupt Handler

When users requests On-Demand instances from a pool to the point that the pool is depleted, the system will select a set of spot instances from the pool to be terminated. A Spot instance pool is a set of unused EC2 instances with the same instance type (for example, m5.large), operating system, Availability Zone, and network platform. The Spot Instance is sent an interruption notice two minutes ahead to gracefully wrap up things.

We will deploy a pod on each spot instance to detect the instance termination notification signal so that we can both terminate gracefully any pod that was running on that node, drain from load balancers and redeploy applications elsewhere in the cluster.

To deploy Spot Interrupt Handler on each Spot Instance we will use a DaemonSet. This will monitor the EC2 metadata service on the instance for a interruption notice.

Within the Spot Interrupt Handler DaemonSet, the workflow can be summarized as:

  • Identify that a Spot Instance is being reclaimed.
  • Use the 2-minute notification window to gracefully prepare the node for termination.
  • Taint the node and cordon it off to prevent new pods from being placed.
  • Drain connections on the running pods.
  • Replace the pods on remaining nodes to maintain the desired capacity.

By default, the aws-node-termination-handler will run on all of your nodes (on-demand and spot). If your spot instances are labeled, you can configure aws-node-termination-handler to only run on your labeled spot nodes. If you’re using the tag lifecycle=Ec2Spot, you can run the following to apply our spot-node-selector overlay.

helm repo add eks https://aws.github.io/eks-charts
helm install --name aws-node-termination-handler \
             --namespace kube-system \
             --set nodeSelector.lifecycle=Ec2Spot \
             eks/aws-node-termination-handler

Verify that the pods are only running on node with label lifecycle=Ec2Spot

kubectl get daemonsets --all-namespaces

Use kube-ops-view to confirm the spot-interrupt-handler-example DaemonSet has been deployed only to EC2 Spot nodes.