EKS nodes drainer

#!/bin/bash
# Drain all nodes gracefully and rely on cluster autoscaler to create new one!

set -e

# Retrieve ASG with tag application=kubernetes
for i in $(aws autoscaling describe-auto-scaling-groups --query 'AutoScalingGroups[?contains(Tags[?Key==`application`].Value, `kubernetes`)].AutoScalingGroupName' --output text) ; do
  cluster=$(echo $i | cut -d'-' -f1)

  echo "Working on cluster $cluster"

  # Add cluster context for kubectl
  aws eks update-kubeconfig --name $cluster

  for j in $(aws autoscaling describe-auto-scaling-groups --query 'AutoScalingGroups[].Instances[].InstanceId' --auto-scaling-group-names $i --output text) ; do
    node=$(aws ec2 describe-instances --instance-ids=$j --query 'Reservations[].Instances[].PrivateDnsName' --output text)
    
    echo "Working on node $node"

    kubectl cordon $node

    #Get all pods running on the node
    for k in $(kubectl get pods --all-namespaces -o=jsonpath="{range .items[?(@.spec.nodeName==\"$node\")]}{.metadata.ownerReferences[0].kind},{.metadata.namespace},{.metadata.ownerReferences[0].name} {end}") ; do
      unset tocheck
      readarray -td, podref <<<"$k"; declare ownerinfo
      if [ ${podref[0]} = "ReplicaSet" ] ; then
        readarray -td, rsref <<<$(kubectl get rs/${podref[2]} -n ${podref[1]} -o=jsonpath="{.metadata.ownerReferences[0].kind},{.metadata.ownerReferences[0].name},{.status.readyReplicas}"); declare rsref
        # Only restart RS that have a single pod
        rollout="kubectl rollout restart ${rsref[0]}/${rsref[1]} -n ${podref[1]}"
        [ x${rsref[2]} = "x1" ] && eval $rollout && tocheck="$rollout ; $tocheck"
      elif [[ ${podref[0]} == "StatefulSet" ]] ; then
        ssreplicas=$(kubectl get statefulset/${podref[2]} -n ${podref[1]} -o=jsonpath="{.status.readyReplicas}")
        # Only restart SS that have a single pod
        rollout="kubectl rollout restart statefulset/${podref[2]} -n ${podref[1]}"
        [ x$ssreplicas = "x1" ] && eval $rollout && tocheck="$rollout ; $tocheck" 
      fi
    done
    # Make sure that everything was restarted
    eval $(echo $tocheck | sed 's/restart/status/g')

    # Finally drain the node and delete it
    kubectl drain --force --ignore-daemonsets --delete-local-data $node && \
      aws autoscaling terminate-instance-in-auto-scaling-group --no-should-decrement-desired-capacity --instance-id=$j
  done
done