Parse TargetGrup names from ARNs

pkg/model/awsmodel/BUILD.bazel

@@ -21,6 +21,7 @@ go_library(
         "//upup/pkg/fi:go_default_library",
         "//upup/pkg/fi/cloudup/awstasks:go_default_library",
         "//upup/pkg/fi/fitasks:go_default_library",
+        "//vendor/github.com/aws/aws-sdk-go/aws/arn:go_default_library",
         "//vendor/github.com/aws/aws-sdk-go/service/ec2:go_default_library",
         "//vendor/k8s.io/apimachinery/pkg/util/sets:go_default_library",
         "//vendor/k8s.io/klog/v2:go_default_library",

pkg/model/awsmodel/autoscalinggroup.go

@@ -18,8 +18,11 @@ package awsmodel
 
 import (
 	"fmt"
+	"sort"
 	"strings"
 
+	"github.com/aws/aws-sdk-go/aws/arn"
+	"github.com/aws/aws-sdk-go/service/ec2"
 	"k8s.io/klog/v2"
 	"k8s.io/kops/pkg/apis/kops"
 	"k8s.io/kops/pkg/featureflag"
@@ -28,8 +31,6 @@ import (
 	"k8s.io/kops/pkg/model/spotinstmodel"
 	"k8s.io/kops/upup/pkg/fi"
 	"k8s.io/kops/upup/pkg/fi/cloudup/awstasks"
-
-	"github.com/aws/aws-sdk-go/service/ec2"
 )
 
 const (
@@ -388,7 +389,7 @@ func (b *AutoscalingGroupModelBuilder) buildAutoScalingGroupTask(c *fi.ModelBuil
 		}
 	}
 
-	for i, extLB := range ig.Spec.ExternalLoadBalancers {
+	for _, extLB := range ig.Spec.ExternalLoadBalancers {
 		if extLB.LoadBalancerName != nil {
 			lb := &awstasks.ClassicLoadBalancer{
 				Name:             extLB.LoadBalancerName,
@@ -400,8 +401,16 @@ func (b *AutoscalingGroupModelBuilder) buildAutoScalingGroupTask(c *fi.ModelBuil
 		}
 
 		if extLB.TargetGroupARN != nil {
+			parsed, err := arn.Parse(fi.StringValue(extLB.TargetGroupARN))
+			if err != nil {
+				return nil, fmt.Errorf("error parsing target grup ARN: %v", err)
+			}
+			resource := strings.Split(parsed.Resource, "/")
+			if len(resource) != 3 || resource[0] != "targetgroup" {
+				return nil, fmt.Errorf("error parsing target grup ARN resource: %q", parsed.Resource)
+			}
 			tg := &awstasks.TargetGroup{
-				Name:   fi.String(fmt.Sprintf("external-tg-%d", i)),
+				Name:   fi.String(resource[1]),
 				ARN:    extLB.TargetGroupARN,
 				Shared: fi.Bool(true),
 			}

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

@@ -90,6 +90,7 @@ go_library(
         "//util/pkg/maps:go_default_library",
         "//util/pkg/slice:go_default_library",
         "//vendor/github.com/aws/aws-sdk-go/aws:go_default_library",
+        "//vendor/github.com/aws/aws-sdk-go/aws/arn:go_default_library",
         "//vendor/github.com/aws/aws-sdk-go/aws/awserr:go_default_library",
         "//vendor/github.com/aws/aws-sdk-go/service/autoscaling:go_default_library",
         "//vendor/github.com/aws/aws-sdk-go/service/ec2:go_default_library",

upup/pkg/fi/cloudup/awstasks/autoscalinggroup.go

@@ -23,6 +23,7 @@ import (
 	"strings"
 
 	"github.com/aws/aws-sdk-go/aws"
+	"github.com/aws/aws-sdk-go/aws/arn"
 	"github.com/aws/aws-sdk-go/service/autoscaling"
 	"k8s.io/klog/v2"
 	"k8s.io/kops/upup/pkg/fi"
@@ -163,7 +164,15 @@ func (e *AutoscalingGroup) Find(c *fi.Context) (*AutoscalingGroup, error) {
 	if len(g.TargetGroupARNs) > 0 {
 		actualTGs := make([]*TargetGroup, 0)
 		for _, tg := range g.TargetGroupARNs {
-			actualTGs = append(actualTGs, &TargetGroup{ARN: aws.String(*tg)})
+			parsed, err := arn.Parse(fi.StringValue(tg))
+			if err != nil {
+				return nil, fmt.Errorf("error parsing target grup ARN: %v", err)
+			}
+			resource := strings.Split(parsed.Resource, "/")
+			if len(resource) != 3 || resource[0] != "targetgroup" {
+				return nil, fmt.Errorf("error parsing target grup ARN resource: %q", parsed.Resource)
+			}
+			actualTGs = append(actualTGs, &TargetGroup{ARN: aws.String(*tg), Name: aws.String(resource[1])})
 		}
 		targetGroups, err := ReconcileTargetGroups(c.Cloud.(awsup.AWSCloud), actualTGs, e.TargetGroups)
 		if err != nil {