feat(route53): Convenience API for creating zone delegations (#1853)

When creating delegation relationship between two `PublicHostedZone`s,
one can now use `zone.addDelegation(otherZone)` instead of manually
creating the `ZoneDelegationRecord` insteance. This reduces the risk of
passing the incorrect name server, or hosting the record on the wrong
end of the relationship (DNS is hard!)

Additionally, fixes a bug in which it was not possible to create a zone
delegation record using a `IHostedZone.hostedZoneNameServers` property
as the array was mapped, which caused the `Fn::GetAtt` stringified list
token to become corrupted.

Fixes #1847

packages/@aws-cdk/aws-route53/lib/hosted-zone.ts

@@ -1,6 +1,7 @@
 import ec2 = require('@aws-cdk/aws-ec2');
 import cdk = require('@aws-cdk/cdk');
 import { HostedZoneImportProps, IHostedZone } from './hosted-zone-ref';
+import { ZoneDelegationRecord } from './records';
 import { CfnHostedZone } from './route53.generated';
 import { validateZoneName } from './util';
 
@@ -112,6 +113,41 @@ export class PublicHostedZone extends HostedZone {
   public addVpc(_vpc: ec2.IVpcNetwork) {
     throw new Error('Cannot associate public hosted zones with a VPC');
   }
+
+  /**
+   * Adds a delegation from this zone to a designated zone.
+   *
+   * @param delegate the zone being delegated to.
+   * @param opts     options for creating the DNS record, if any.
+   */
+  public addDelegation(delegate: PublicHostedZone, opts: ZoneDelegationOptions = {}): void {
+    new ZoneDelegationRecord(this, `${this.zoneName} -> ${delegate.zoneName}`, {
+      zone: this,
+      delegatedZoneName: delegate.zoneName,
+      nameServers: delegate.hostedZoneNameServers!, // PublicHostedZones always have name servers!
+      comment: opts.comment,
+      ttl: opts.ttl,
+    });
+  }
+}
+
+/**
+ * Options available when creating a delegation relationship from one PublicHostedZone to another.
+ */
+export interface ZoneDelegationOptions {
+  /**
+   * A comment to add on the DNS record created to incorporate the delegation.
+   *
+   * @default none
+   */
+  comment?: string;
+
+  /**
+   * The TTL (Time To Live) of the DNS delegation record in DNS caches.
+   *
+   * @default 172800
+   */
+  ttl?: number;
 }
 
 export interface PrivateHostedZoneProps extends CommonHostedZoneProps {

packages/@aws-cdk/aws-route53/lib/records/zone-delegation.ts

@@ -1,9 +1,10 @@
-import { Construct } from '@aws-cdk/cdk';
+import cdk = require('@aws-cdk/cdk');
+import { ZoneDelegationOptions } from '../hosted-zone';
 import { IHostedZone } from '../hosted-zone-ref';
 import { CfnRecordSet } from '../route53.generated';
 import { determineFullyQualifiedDomainName } from './_util';
 
-export interface ZoneDelegationRecordProps {
+export interface ZoneDelegationRecordProps extends ZoneDelegationOptions {
   /**
    * The zone in which this delegate is defined.
    */
@@ -17,38 +18,27 @@ export interface ZoneDelegationRecordProps {
    * The name servers to report in the delegation records.
    */
   nameServers: string[];
-
-  /**
-   * The TTL of the zone delegation records.
-   *
-   * @default 172800 seconds.
-   */
-  ttl?: number;
-
-  /**
-   * Any comments that you want to include about the zone delegation records.
-   *
-   * @default no comment.
-   */
-  comment?: string;
 }
 
 /**
  * A record to delegate further lookups to a different set of name servers
  */
-export class ZoneDelegationRecord extends Construct {
-  constructor(scope: Construct, id: string, props: ZoneDelegationRecordProps) {
+export class ZoneDelegationRecord extends cdk.Construct {
+  constructor(scope: cdk.Construct, id: string, props: ZoneDelegationRecordProps) {
     super(scope, id);
 
     const ttl = props.ttl === undefined ? 172_800 : props.ttl;
+    const resourceRecords = cdk.unresolved(props.nameServers)
+      ? props.nameServers // Can't map a string-array token!
+      : props.nameServers.map(ns => (cdk.unresolved(ns) || ns.endsWith('.')) ? ns : `${ns}.`);
 
     new CfnRecordSet(this, 'Resource', {
       hostedZoneId: props.zone.hostedZoneId,
       name: determineFullyQualifiedDomainName(props.delegatedZoneName, props.zone),
       type: 'NS',
       ttl: ttl.toString(),
       comment: props.comment,
-      resourceRecords: props.nameServers.map(ns => ns.endsWith('.') ? ns : `${ns}.`)
+      resourceRecords,
     });
   }
 }

packages/@aws-cdk/aws-route53/test/integ.route53.expected.json

@@ -532,6 +532,29 @@
         "Name": "cdk.test."
       }
     },
+    "PublicZonecdktestsubcdktest83558650": {
+      "Type": "AWS::Route53::RecordSet",
+      "Properties": {
+        "Name": "sub.cdk.test.",
+        "Type": "NS",
+        "HostedZoneId": {
+          "Ref": "PublicZone2E1C4E34"
+        },
+        "ResourceRecords": {
+          "Fn::GetAtt": [
+            "PublicSubZoneDBD26A0A",
+            "NameServers"
+          ]
+        },
+        "TTL": "172800"
+      }
+    },
+    "PublicSubZoneDBD26A0A": {
+      "Type": "AWS::Route53::HostedZone",
+      "Properties": {
+        "Name": "sub.cdk.test."
+      }
+    },
     "CNAMEC70A2D52": {
       "Type": "AWS::Route53::RecordSet",
       "Properties": {
@@ -559,4 +582,4 @@
       }
     }
   }
-}
+}

packages/@aws-cdk/aws-route53/test/integ.route53.ts

@@ -15,6 +15,10 @@ const privateZone = new PrivateHostedZone(stack, 'PrivateZone', {
 const publicZone = new PublicHostedZone(stack, 'PublicZone', {
   zoneName: 'cdk.test'
 });
+const publicSubZone = new PublicHostedZone(stack, 'PublicSubZone', {
+  zoneName: 'sub.cdk.test'
+});
+publicZone.addDelegation(publicSubZone);
 
 new TxtRecord(privateZone, 'TXT', {
   zone: privateZone,

packages/@aws-cdk/aws-route53/test/test.route53.ts

@@ -192,7 +192,27 @@ export = {
     // THEN
     test.throws(() => zone.addVpc(vpc), /Cannot associate public hosted zones with a VPC/);
     test.done();
-  }
+  },
+
+  'setting up zone delegation'(test: Test) {
+    // GIVEN
+    const stack = new cdk.Stack();
+    const zone = new PublicHostedZone(stack, 'TopZone', { zoneName: 'top.test' });
+    const delegate = new PublicHostedZone(stack, 'SubZone', { zoneName: 'sub.top.test' });
+
+    // WHEN
+    zone.addDelegation(delegate, { ttl: 1337 });
+
+    // THEN
+    expect(stack).to(haveResource('AWS::Route53::RecordSet', {
+      Type: 'NS',
+      Name: 'sub.top.test.',
+      HostedZoneId: zone.node.resolve(zone.hostedZoneId),
+      ResourceRecords: zone.node.resolve(delegate.hostedZoneNameServers),
+      TTL: '1337',
+    }));
+    test.done();
+  },
 };
 
 class TestApp {