kubernetes/kops · error

error attaching LoadBalancers: %v

Error message

error attaching LoadBalancers: %v

What it means

AttachLoadBalancers failed while attaching classic ELBs to the ASG; the ASG was updated but the load balancer attachment is incomplete. The wrapped error is the raw AWS autoscaling API error.

Source

Thrown at upup/pkg/fi/cloudup/awstasks/autoscalinggroup.go:682

		if deleteTagsRequest != nil && len(deleteTagsRequest.Tags) > 0 {
			if _, err := t.Cloud.Autoscaling().DeleteTags(ctx, deleteTagsRequest); err != nil {
				return fmt.Errorf("error deleting old AutoscalingGroup tags: %v", err)
			}
		}
		if updateTagsRequest != nil {
			if _, err := t.Cloud.Autoscaling().CreateOrUpdateTags(ctx, updateTagsRequest); err != nil {
				return fmt.Errorf("error updating AutoscalingGroup tags: %v", err)
			}
		}

		if detachLBRequest != nil {
			if _, err := t.Cloud.Autoscaling().DetachLoadBalancers(ctx, detachLBRequest); err != nil {
				return fmt.Errorf("error detatching LoadBalancers: %v", err)
			}
		}
		if attachLBRequest != nil {
			if _, err := t.Cloud.Autoscaling().AttachLoadBalancers(ctx, attachLBRequest); err != nil {
				return fmt.Errorf("error attaching LoadBalancers: %v", err)
			}
		}
		if len(attachTGRequests) > 0 {
			for _, attachTGRequest := range attachTGRequests {
				if _, err := t.Cloud.Autoscaling().AttachLoadBalancerTargetGroups(ctx, attachTGRequest); err != nil {
					return fmt.Errorf("failed to attach target groups: %v", err)
				}
			}
		}
	}

	return nil
}

// UseMixedInstancesPolicy checks if we should add a mixed instances policy to the asg
func (e *AutoscalingGroup) UseMixedInstancesPolicy() bool {
	if e.LaunchTemplate == nil {
		return false

View on GitHub (pinned to 4c8573c808)

Solutions

1. Verify the load balancer name in the instance group spec exists in the same region/VPC as the ASG subnets.
2. Ensure kops created the ELB first (run full `kops update cluster --yes`, not a partial apply).
3. Check IAM permissions include autoscaling:AttachLoadBalancers and ELB read access.
4. Retry after backoff if throttled.

Example fix

// before: wrong region ELB name
loadBalancer:
  loadBalancerName: my-elb-eu-west-1
// after: kops-managed attachment
loadBalancer:
  targetGroupArn: <arn-in-same-vpc>

// verify ELB exists in the ASG region/VPC before attach
out, err := elbSvc.DescribeLoadBalancers(&elb.DescribeLoadBalancersInput{LoadBalancerNames: []string{lbName}})
if err != nil || len(out.LoadBalancerDescriptions) == 0 {
  return fmt.Errorf("ELB %s missing or wrong region", lbName)
}

if _, err := svc.AttachLoadBalancers(ctx, req); err != nil {
  var ae smithy.APIError
  if errors.As(err, &ae) && ae.ErrorCode() == "ValidationError" {
    return fmt.Errorf("check ELB name/VPC in instanceGroup spec: %w", err)
  }
  return retry(err)
}

When it happens

Trigger: During ASG update, attachLBRequest is built (a classic load balancer added to the ASG spec) and Autoscaling().AttachLoadBalancers fails: ELB not found or in wrong region/VPC, ELB deleted between check and use, throttling, or missing autoscaling:AttachLoadBalancers permission.

Common situations: Adding a loadBalancer attachment to an instance group while the ELB name is misspelled; ELB lives in a different VPC than the ASG subnets; cross-account ELB not shared; throttling during big applies.

Related errors

• error detatching LoadBalancers: %v
• error updating AutoscalingGroup: %v
• error deleting old AutoscalingGroup tags: %v
• error updating AutoscalingGroup tags: %v
• failed to attach target groups: %v

AI-assisted analysis of kubernetes/kops@4c8573c808 (2026-09-05). Data as JSON: /api/errors/80d69bb79c888b43. Report an issue: GitHub.