add instance connection draining for NLBs

upup/pkg/fi/cloudup/awsup/BUILD.bazel

@@ -56,6 +56,7 @@ go_library(
         "//vendor/github.com/aws/aws-sdk-go/service/sqs:go_default_library",
         "//vendor/github.com/aws/aws-sdk-go/service/sqs/sqsiface:go_default_library",
         "//vendor/github.com/aws/aws-sdk-go/service/sts:go_default_library",
+        "//vendor/golang.org/x/sync/errgroup:go_default_library",
         "//vendor/k8s.io/api/core/v1:go_default_library",
         "//vendor/k8s.io/apimachinery/pkg/util/sets:go_default_library",
         "//vendor/k8s.io/klog/v2:go_default_library",

upup/pkg/fi/cloudup/awsup/aws_cloud.go

@@ -27,6 +27,7 @@ import (
 	"github.com/aws/aws-sdk-go/service/eventbridge/eventbridgeiface"
 	"github.com/aws/aws-sdk-go/service/sqs"
 	"github.com/aws/aws-sdk-go/service/sqs/sqsiface"
+	"golang.org/x/sync/errgroup"
 
 	"github.com/aws/aws-sdk-go/aws"
 	"github.com/aws/aws-sdk-go/aws/arn"
@@ -547,7 +548,7 @@ func deleteInstance(c AWSCloud, i *cloudinstances.CloudInstance) error {
 	}
 
 	if i.CloudInstanceGroup.InstanceGroup.Spec.Manager != kops.InstanceManagerKarpenter {
-		err := deregisterInstanceFromClassicLoadBalancer(c, i)
+		err := deregisterInstance(c, i)
 		if err != nil {
 			return fmt.Errorf("failed to deregister instance from loadBalancer before terminating: %v", err)
 		}
@@ -570,9 +571,8 @@ func deleteInstance(c AWSCloud, i *cloudinstances.CloudInstance) error {
 	return nil
 }
 
-// deregisterInstanceFromClassicLoadBalancer ensures that connectionDraining completes for the associated loadBalancer to ensure no dropped connections.
-// if instance is associated with an NLB, this method no-ops.
-func deregisterInstanceFromClassicLoadBalancer(c AWSCloud, i *cloudinstances.CloudInstance) error {
+// deregisterInstance ensures that the instance is fully drained/removed from all associated loadBalancers and targetGroups before termination.
+func deregisterInstance(c AWSCloud, i *cloudinstances.CloudInstance) error {
 	asg := i.CloudInstanceGroup.Raw.(*autoscaling.Group)
 
 	asgDetails, err := c.Autoscaling().DescribeAutoScalingGroups(&autoscaling.DescribeAutoScalingGroupsInput{
@@ -587,17 +587,41 @@ func deregisterInstanceFromClassicLoadBalancer(c AWSCloud, i *cloudinstances.Clo
 	}
 
 	// there will always be only one ASG in the DescribeAutoScalingGroups response.
-	loadBalancerNames := asgDetails.AutoScalingGroups[0].LoadBalancerNames
+	loadBalancerNames := aws.StringValueSlice(asgDetails.AutoScalingGroups[0].LoadBalancerNames)
+	targetGroupArns := aws.StringValueSlice(asgDetails.AutoScalingGroups[0].TargetGroupARNs)
 
-	klog.Infof("Deregistering instance from classic loadBalancers: %v", aws.StringValueSlice(loadBalancerNames))
+	eg, _ := errgroup.WithContext(aws.BackgroundContext())
+
+	if len(loadBalancerNames) != 0 {
+		eg.Go(func() error {
+			return deregisterInstanceFromClassicLoadBalancer(c, loadBalancerNames, i.ID)
+		})
+	}
+
+	if len(targetGroupArns) != 0 {
+		eg.Go(func() error {
+			return deregisterInstanceFromTargetGroups(c, targetGroupArns, i.ID)
+		})
+	}
+
+	if err := eg.Wait(); err != nil {
+		return fmt.Errorf("failed to deregister instance from load balancers: %v", err)
+	}
+
+	return nil
+}
+
+// deregisterInstanceFromClassicLoadBalancer ensures that connectionDraining completes for the associated classic loadBalancer to ensure no dropped connections.
+func deregisterInstanceFromClassicLoadBalancer(c AWSCloud, loadBalancerNames []string, instanceId string) error {
+	klog.Infof("Deregistering instance from classic loadBalancers: %v", loadBalancerNames)
 
 	for {
 		instanceDraining := false
 		for _, loadBalancerName := range loadBalancerNames {
 			response, err := c.ELB().DescribeInstanceHealth(&elb.DescribeInstanceHealthInput{
-				LoadBalancerName: loadBalancerName,
+				LoadBalancerName: aws.String(loadBalancerName),
 				Instances: []*elb.Instance{{
-					InstanceId: aws.String(i.ID),
+					InstanceId: aws.String(instanceId),
 				}},
 			})
 			if err != nil {
@@ -612,9 +636,9 @@ func deregisterInstanceFromClassicLoadBalancer(c AWSCloud, i *cloudinstances.Clo
 			// there will be only one instance in the DescribeInstanceHealth response.
 			if aws.StringValue(response.InstanceStates[0].State) == instanceInServiceState {
 				c.ELB().DeregisterInstancesFromLoadBalancer(&elb.DeregisterInstancesFromLoadBalancerInput{
-					LoadBalancerName: loadBalancerName,
+					LoadBalancerName: aws.String(loadBalancerName),
 					Instances: []*elb.Instance{{
-						InstanceId: aws.String(i.ID),
+						InstanceId: aws.String(instanceId),
 					}},
 				})
 				instanceDraining = true
@@ -627,7 +651,48 @@ func deregisterInstanceFromClassicLoadBalancer(c AWSCloud, i *cloudinstances.Clo
 
 		time.Sleep(5 * time.Second)
 	}
+	return nil
+}
 
+// deregisterInstanceFromTargetGroups ensures that instances are fully unused in the corresponding targetGroups before instance termination.
+// this ensures that connections are fully drained from the instance before terminating.
+func deregisterInstanceFromTargetGroups(c AWSCloud, targetGroupArns []string, instanceId string) error {
+	klog.Infof("Deregistering instance from targetGroups: %v", targetGroupArns)
+
+	for {
+		instanceDraining := false
+		for _, targetGroupArn := range targetGroupArns {
+			response, err := c.ELBV2().DescribeTargetHealth(&elbv2.DescribeTargetHealthInput{
+				TargetGroupArn: aws.String(targetGroupArn),
+				Targets: []*elbv2.TargetDescription{{
+					Id: aws.String(instanceId),
+				}},
+			})
+
+			if err != nil {
+				return fmt.Errorf("error describing target health: %v", err)
+			}
+
+			// there will be only one target in the DescribeTargetHealth response.
+			// DescribeTargetHealth response will contain a target even if the targetId doesn't exist.
+			// all other states besides TargetHealthStateUnused means that the instance may still be serving traffic.
+			if aws.StringValue(response.TargetHealthDescriptions[0].TargetHealth.State) != elbv2.TargetHealthStateEnumUnused {
+				c.ELBV2().DeregisterTargets(&elbv2.DeregisterTargetsInput{
+					TargetGroupArn: aws.String(targetGroupArn),
+					Targets: []*elbv2.TargetDescription{{
+						Id: aws.String(instanceId),
+					}},
+				})
+				instanceDraining = true
+			}
+		}
+
+		if !instanceDraining {
+			break
+		}
+
+		time.Sleep(5 * time.Second)
+	}
 	return nil
 }