kubernetes/kops · error

DNSName not set on AliasTarget

Error message

DNSName not set on AliasTarget

What it means

findNetworkLoadBalancerByAlias matches an ELBv2 Alias target (e.g. from a Route53 record) against existing NLBs by DNS name. If alias.DNSName is empty after trimming a trailing dot, the function cannot match anything and returns "DNSName not set on AliasTarget".

Source

Thrown at upup/pkg/fi/cloudup/awstasks/network_load_balancer.go:113

var _ fi.CompareWithID = (*NetworkLoadBalancer)(nil)
var _ fi.CloudupTaskNormalize = (*NetworkLoadBalancer)(nil)
var _ fi.CloudupProducesDeletions = (*NetworkLoadBalancer)(nil)

func (e *NetworkLoadBalancer) CompareWithID() *string {
	return e.Name
}

func findNetworkLoadBalancerByAlias(cloud awsup.AWSCloud, alias *route53types.AliasTarget) (*elbv2types.LoadBalancer, error) {
	ctx := context.TODO()

	// TODO: Any way to avoid listing all NLBs?
	request := &elbv2.DescribeLoadBalancersInput{}

	dnsName := aws.ToString(alias.DNSName)
	matchDnsName := strings.TrimSuffix(dnsName, ".")
	if matchDnsName == "" {
		return nil, fmt.Errorf("DNSName not set on AliasTarget")
	}

	matchHostedZoneId := aws.ToString(alias.HostedZoneId)

	found, err := describeNetworkLoadBalancers(ctx, cloud, request, func(lb elbv2types.LoadBalancer) bool {
		if matchHostedZoneId != aws.ToString(lb.CanonicalHostedZoneId) {
			return false
		}

		lbDnsName := aws.ToString(lb.DNSName)
		lbDnsName = strings.TrimSuffix(lbDnsName, ".")
		return lbDnsName == matchDnsName || "dualstack."+lbDnsName == matchDnsName
	})
	if err != nil {
		return nil, fmt.Errorf("error listing NLBs: %v", err)
	}

	if len(found) == 0 {

View on GitHub (pinned to 4c8573c808)

Solutions

1. Inspect the Route53 record and set the correct AliasTarget DNSName (the NLB's dns name)
2. If the record is broken/unwanted, delete or recreate the alias record with a valid target
3. Re-run kops update once the alias record carries a DNSName

Example fix

// before (alias target)
{ HostedZoneId: "Z..." } // DNSName missing
// after
{ HostedZoneId: "Z...", DNSName: "k8s-elb-xxx.elb.us-east-1.amazonaws.com" }

if alias != nil && (alias.DNSName == nil || strings.TrimSuffix(aws.ToString(alias.DNSName), ".") == "") {
    return fmt.Errorf("route53 alias target has no DNSName; fix the record before update")
}

func aliasHasDNSName(a *route53types.AliasTarget) bool {
    return a != nil && strings.TrimSuffix(aws.ToString(a.DNSName), ".") != ""
}

When it happens

Trigger: Called from findDNSTargetNLB when a Route53 A/AAAA alias record's AliasTarget has a nil or empty DNSName field while kOps tries to determine whether the record already points at an NLB.

Common situations: Corrupt or manually edited Route53 alias record; record built programmatically with DNSName omitted; AWS SDK change exposing nil DNSName on an alias target.

Related errors

• error mapping DNSName %q to LoadBalancer: %v
• Found NLB %q linked to DNS name %q, but it did not have a Na
• error applying DNS changeset for zone %s: %v
• failed to load default aws config for IMDS client: %w
• failed to load default aws config for STS client: %w

AI-assisted analysis of kubernetes/kops@4c8573c808 (2026-09-05). Data as JSON: /api/errors/86f3f0fe9db6deb5. Report an issue: GitHub.