Fix: order must match specified subnets

Author: wweiwei-li

pkg/service/model_build_load_balancer.go

@@ -300,11 +300,17 @@ func (t *defaultModelBuildTask) buildLoadBalancerTags(ctx context.Context) (map[
 func (t *defaultModelBuildTask) buildLoadBalancerSubnetMappings(_ context.Context, ipAddressType elbv2model.IPAddressType, scheme elbv2model.LoadBalancerScheme, ec2Subnets []ec2types.Subnet) ([]elbv2model.SubnetMapping, error) {
 	var eipAllocation []string
 	eipConfigured := t.annotationParser.ParseStringSliceAnnotation(annotations.SvcLBSuffixEIPAllocations, &eipAllocation, t.service.Annotations)
+	var subnetsId []string
+	subnetIDConfigured := t.annotationParser.ParseStringSliceAnnotation(annotations.SvcLBSuffixSubnets, &subnetsId, t.service.Annotations)
+	reorderedSubnets := append(ec2Subnets[:0:0], ec2Subnets...)
+	if subnetIDConfigured {
+		reorderedSubnets = sortSubnetsBySubnetIdConfigured(subnetsId, ec2Subnets)
+	}
 	if eipConfigured {
 		if scheme != elbv2model.LoadBalancerSchemeInternetFacing {
 			return nil, errors.Errorf("EIP allocations can only be set for internet facing load balancers")
 		}
-		if len(eipAllocation) != len(ec2Subnets) {
+		if len(eipAllocation) != len(reorderedSubnets) {
 			return nil, errors.Errorf("count of EIP allocations (%d) and subnets (%d) must match", len(eipAllocation), len(ec2Subnets))
 		}
 	}
@@ -317,7 +323,7 @@ func (t *defaultModelBuildTask) buildLoadBalancerSubnetMappings(_ context.Contex
 			return nil, errors.Errorf("private IPv4 addresses can only be set for internal load balancers")
 		}
 		// TODO: consider relax this requirement as ELBv2 API don't require every subnet to have IPv4 address specified.
-		if len(rawIPv4Addresses) != len(ec2Subnets) {
+		if len(rawIPv4Addresses) != len(reorderedSubnets) {
 			return nil, errors.Errorf("count of private IPv4 addresses (%d) and subnets (%d) must match", len(rawIPv4Addresses), len(ec2Subnets))
 		}
 		for _, rawIPv4Address := range rawIPv4Addresses {
@@ -340,7 +346,7 @@ func (t *defaultModelBuildTask) buildLoadBalancerSubnetMappings(_ context.Contex
 			return nil, errors.Errorf("IPv6 addresses can only be set for dualstack load balancers")
 		}
 		// TODO: consider relax this requirement as ELBv2 API don't require every subnet to have IPv6 address specified.
-		if len(rawIPv6Addresses) != len(ec2Subnets) {
+		if len(rawIPv6Addresses) != len(reorderedSubnets) {
 			return nil, errors.Errorf("count of IPv6 addresses (%d) and subnets (%d) must match", len(rawIPv6Addresses), len(ec2Subnets))
 		}
 		for _, rawIPv6Address := range rawIPv6Addresses {
@@ -355,8 +361,8 @@ func (t *defaultModelBuildTask) buildLoadBalancerSubnetMappings(_ context.Contex
 		}
 	}
 
-	subnetMappings := make([]elbv2model.SubnetMapping, 0, len(ec2Subnets))
-	for idx, subnet := range ec2Subnets {
+	subnetMappings := make([]elbv2model.SubnetMapping, 0, len(reorderedSubnets))
+	for idx, subnet := range reorderedSubnets {
 		mapping := elbv2model.SubnetMapping{
 			SubnetID: awssdk.ToString(subnet.SubnetId),
 		}
@@ -534,3 +540,15 @@ func (t *defaultModelBuildTask) buildLoadBalancerName(_ context.Context, scheme
 	sanitizedName := invalidLoadBalancerNamePattern.ReplaceAllString(t.service.Name, "")
 	return fmt.Sprintf("k8s-%.8s-%.8s-%.10s", sanitizedNamespace, sanitizedName, uuid), nil
 }
+
+func sortSubnetsBySubnetIdConfigured(subnetId []string, ec2Subnets []ec2types.Subnet) []ec2types.Subnet {
+	subnetIndex := make(map[string]int)
+	for index, id := range subnetId {
+		subnetIndex[id] = index
+	}
+	sortedSubnets := append(ec2Subnets[:0:0], ec2Subnets...)
+	sort.Slice(sortedSubnets, func(i, j int) bool {
+		return subnetIndex[*sortedSubnets[i].SubnetId] < subnetIndex[*sortedSubnets[j].SubnetId]
+	})
+	return sortedSubnets
+}

pkg/service/model_build_load_balancer_test.go

@@ -3,9 +3,11 @@ package service
 import (
 	"context"
 	"errors"
+	"testing"
+
+	awssdk "github.com/aws/aws-sdk-go-v2/aws"
 	ec2types "github.com/aws/aws-sdk-go-v2/service/ec2/types"
 	elbv2types "github.com/aws/aws-sdk-go-v2/service/elasticloadbalancingv2/types"
-	"testing"
 
 	"k8s.io/apimachinery/pkg/util/sets"
 	"sigs.k8s.io/aws-load-balancer-controller/pkg/model/core"
@@ -1445,3 +1447,78 @@ func Test_defaultModelBuildTask_buildLoadBalancerName(t *testing.T) {
 		})
 	}
 }
+
+func Test_sortSubnetsBySubnetIdConfigured(t *testing.T) {
+	type args struct {
+		subnetId   []string
+		ec2Subnets []ec2types.Subnet
+	}
+	tests := []struct {
+		name        string
+		args        args
+		wantSubnets []ec2types.Subnet
+	}{
+		{
+			name: "Sorting",
+			args: args{
+				subnetId: []string{"subnet-a", "subnet-b", "subnet-c"},
+				ec2Subnets: []ec2types.Subnet{
+					{
+						SubnetId: awssdk.String("subnet-b"),
+					},
+					{
+						SubnetId: awssdk.String("subnet-a"),
+					},
+					{
+						SubnetId: awssdk.String("subnet-c"),
+					},
+				},
+			},
+			wantSubnets: []ec2types.Subnet{
+				{
+					SubnetId: awssdk.String("subnet-a"),
+				},
+				{
+					SubnetId: awssdk.String("subnet-b"),
+				},
+				{
+					SubnetId: awssdk.String("subnet-c"),
+				},
+			},
+		},
+		{
+			name: "sorted subnets",
+			args: args{
+				subnetId: []string{"subnet-a", "subnet-b", "subnet-c"},
+				ec2Subnets: []ec2types.Subnet{
+					{
+						SubnetId: awssdk.String("subnet-a"),
+					},
+					{
+						SubnetId: awssdk.String("subnet-b"),
+					},
+					{
+						SubnetId: awssdk.String("subnet-c"),
+					},
+				},
+			},
+			wantSubnets: []ec2types.Subnet{
+				{
+					SubnetId: awssdk.String("subnet-a"),
+				},
+				{
+					SubnetId: awssdk.String("subnet-b"),
+				},
+				{
+					SubnetId: awssdk.String("subnet-c"),
+				},
+			},
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			result := sortSubnetsBySubnetIdConfigured(tt.args.subnetId, tt.args.ec2Subnets)
+			assert.Equal(t, tt.wantSubnets, result)
+		})
+	}
+}