retry on CNAME conflicts

Author: lionello

main.go

@@ -8,6 +8,7 @@ import (
 	"net/http"
 	"os"
 	"os/signal"
+	"strings"
 	"syscall"
 	"time"
 
@@ -29,14 +30,19 @@ var (
 
 	register, unRegister bool
 
-	r53 *route53.Client
+	r53 Route53Client
 )
 
+type Route53Client interface {
+	ChangeResourceRecordSets(ctx context.Context, params *route53.ChangeResourceRecordSetsInput, optFns ...func(*route53.Options)) (*route53.ChangeResourceRecordSetsOutput, error)
+	GetChange(ctx context.Context, params *route53.GetChangeInput, optFns ...func(*route53.Options)) (*route53.GetChangeOutput, error)
+}
+
 func configureFromFlags(ctx context.Context) {
 	flag.StringVar(&dns, "dns", "my.example.com", "DNS name to register in Route53")
 	flag.StringVar(&hostedZone, "hostedzone", "Z2AAAABCDEFGT4", "Hosted zone ID in route53")
 	flag.IntVar(&dnsTTL, "dnsttl", 10, "Timeout for DNS entry")
-	flag.StringVar(&ipAddress, "ipaddress", "public-ipv4", "IP Address for A Record")
+	flag.StringVar(&ipAddress, "ipaddress", "1.2.4.5", "IP Address for A Record")
 	flag.BoolVar(&register, "register", false, "Register DNS and exit")
 	flag.BoolVar(&unRegister, "unregister", false, "Unregister DNS and exit")
 	flag.Parse()
@@ -122,7 +128,7 @@ func tearDownDNS(ctx context.Context) {
 	log.Print("DNS Timeout expiry finished")
 }
 
-func setupDNS(ctx context.Context) {
+func setupDNS(ctx context.Context) error {
 	log.Printf("Setting up Route 53 DNS Name A %s => %s", dns, ipAddress)
 
 	input := &route53.ChangeResourceRecordSetsInput{
@@ -149,22 +155,34 @@ func setupDNS(ctx context.Context) {
 		HostedZoneId: aws.String(hostedZone),
 	}
 
-	changeSet, err := r53.ChangeResourceRecordSets(ctx, input)
-	if err != nil {
-		log.Printf("Failed to create DNS: %v", err.Error())
-		return
+	var changeSet *route53.ChangeResourceRecordSetsOutput
+	for {
+		var err error
+		changeSet, err = r53.ChangeResourceRecordSets(ctx, input)
+		if err != nil {
+			if !strings.Contains(err.Error(), "conflicting RRSet of type CNAME") {
+				log.Printf("Failed to create DNS: %v", err.Error())
+				return err
+			}
+			// If the error is due to a conflicting CNAME, wait and try again
+			if err := SleepWithContext(ctx, 5*time.Second); err != nil {
+				return err
+			}
+			continue
+		}
+		break
 	}
 
 	log.Print("Request sent to Route 53...")
-	waitForSync(ctx, changeSet)
+	return waitForSync(ctx, changeSet)
 }
 
-func waitForSync(ctx context.Context, changeSet *route53.ChangeResourceRecordSetsOutput) {
+func waitForSync(ctx context.Context, changeSet *route53.ChangeResourceRecordSetsOutput) error {
 	failures := 0
 	for {
 		if err := SleepWithContext(ctx, 5*time.Second); err != nil {
 			log.Print("Context cancelled, stop waiting for Route53 ChangeSet to propogate")
-			return
+			return err
 		}
 
 		changeOutput, err := r53.GetChange(ctx, &route53.GetChangeInput{
@@ -181,7 +199,7 @@ func waitForSync(ctx context.Context, changeSet *route53.ChangeResourceRecordSet
 
 		if changeOutput.ChangeInfo.Status == "INSYNC" {
 			log.Print("Route53 Change Completed")
-			break
+			return nil
 		}
 
 		log.Printf("Route53 Change not yet propogated (ChangeInfo.Status = %s)...", changeOutput.ChangeInfo.Status)

main_test.go

@@ -1,10 +1,17 @@
 package main
 
 import (
+	"context"
 	"net/http"
 	"net/http/httptest"
 	"os"
 	"testing"
+
+	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/service/route53"
+	"github.com/aws/aws-sdk-go-v2/service/route53/types"
+	"github.com/aws/smithy-go"
+	"github.com/aws/smithy-go/ptr"
 )
 
 func Test_getEcsMetadata(t *testing.T) {
@@ -14,7 +21,7 @@ func Test_getEcsMetadata(t *testing.T) {
 		w.Write([]byte(`{"Name":"curl","Networks":[{"IPv4Addresses":["` + want + `"]}]}`))
 	})
 	server := httptest.NewServer(handler)
-	defer server.Close()
+	t.Cleanup(server.Close)
 
 	os.Setenv("ECS_CONTAINER_METADATA_URI_V4", server.URL)
 
@@ -27,3 +34,59 @@ func Test_getEcsMetadata(t *testing.T) {
 		t.Errorf("getEcsMetadata() = %v, want %v", got, want)
 	}
 }
+
+type mockRoute53 struct {
+	calls    int
+	wantErrs []error
+}
+
+func (m *mockRoute53) ChangeResourceRecordSets(ctx context.Context, input *route53.ChangeResourceRecordSetsInput, opts ...func(*route53.Options)) (*route53.ChangeResourceRecordSetsOutput, error) {
+	var err error
+	if m.calls < len(m.wantErrs) {
+		err = m.wantErrs[m.calls]
+	}
+	m.calls++
+	return &route53.ChangeResourceRecordSetsOutput{
+		ChangeInfo: &types.ChangeInfo{
+			Id: aws.String("mockChangeId"),
+		},
+	}, err
+}
+
+func (m *mockRoute53) GetChange(ctx context.Context, input *route53.GetChangeInput, opts ...func(*route53.Options)) (*route53.GetChangeOutput, error) {
+	return &route53.GetChangeOutput{
+		ChangeInfo: &types.ChangeInfo{
+			Status: types.ChangeStatusInsync,
+		},
+	}, nil
+}
+
+func Test_setupDNS(t *testing.T) {
+	ctx := context.Background()
+
+	dns = "cname.nextjs.internal."
+	ipAddress = "1.2.3.4"
+
+	t.Run("success", func(t *testing.T) {
+		r53 = &mockRoute53{}
+
+		if err := setupDNS(ctx); err != nil {
+			t.Errorf("setupDNS() error = %v", err)
+		}
+	})
+
+	t.Run("retries", func(t *testing.T) {
+		r53 = &mockRoute53{
+			wantErrs: []error{&smithy.OperationError{
+				ServiceID:     "Route 53",
+				OperationName: "ChangeResourceRecordSets",
+				Err: &types.InvalidChangeBatch{
+					Message: ptr.String("[RRSet of type A with DNS name cname.nextjs.internal. is not permitted because a conflicting RRSet of type CNAME with the same DNS name already exists in zone nextjs.internal.]"),
+				},
+			}},
+		}
+		if err := setupDNS(ctx); err != nil {
+			t.Errorf("setupDNS() error = %v", err)
+		}
+	})
+}