feat(rds): support local write forwarding for an aurora PostgreSQL cluster

packages/@aws-cdk-testing/framework-integ/test/aws-rds/test/integ.cluster-enable-local-write-forwarding.ts

@@ -18,6 +18,16 @@ new rds.DatabaseCluster(stack, 'DatabaseCluster', {
   enableLocalWriteForwarding: true,
 });
 
+new rds.DatabaseCluster(stack, 'DatabaseClusterPostgresql', {
+  engine: rds.DatabaseClusterEngine.auroraPostgres({ version: rds.AuroraPostgresEngineVersion.VER_16_4 }),
+  writer: rds.ClusterInstance.serverlessV2('writerInstance'),
+  readers: [
+    rds.ClusterInstance.serverlessV2('readerInstance1'),
+  ],
+  vpc,
+  enableLocalWriteForwarding: true,
+});
+
 new integ.IntegTest(app, 'EnableLocalWriteForwardingClusterStackInteg', {
   testCases: [stack],
 });

packages/aws-cdk-lib/aws-rds/README.md

@@ -102,7 +102,8 @@ new rds.DatabaseCluster(this, 'DatabaseCluster', {
 });
 ```
 
-**Note**: Local write forwarding is only supported for Aurora MySQL 3.04 and higher.
+**Note**: Local write forwarding is supported only for Aurora MySQL 3.04 or higher, and for Aurora PostgreSQL
+16.4 or higher (for version 16), 15.8 or higher (for version 15), and 14.13 or higher (for version 14).
 
 Use `DatabaseClusterFromSnapshot` to create a cluster from a snapshot:
 

packages/aws-cdk-lib/aws-rds/lib/cluster.ts

@@ -389,9 +389,11 @@ interface DatabaseClusterBaseProps {
   /**
    * Whether read replicas can forward write operations to the writer DB instance in the DB cluster.
    *
-   * This setting can only be enabled for Aurora MySQL 3.04 and higher clusters.
+   * This setting can only be enabled for Aurora MySQL 3.04 or higher, and for Aurora PostgreSQL 16.4
+   * or higher (for version 16), 15.8 or higher (for version 15), and 14.13 or higher (for version 14).
    *
    * @see https://docs.aws.amazon.com/AmazonRDS/latest/AuroraUserGuide/aurora-mysql-write-forwarding.html
+   * @see https://docs.aws.amazon.com/AmazonRDS/latest/AuroraUserGuide/aurora-postgresql-write-forwarding.html
    *
    * @default false
    */
@@ -737,11 +739,6 @@ abstract class DatabaseClusterNew extends DatabaseClusterBase {
       });
     }
 
-    // enableLocalWriteForwarding cannot be configured, including false, on Aurora clusters other than MySQL.
-    if (props.enableLocalWriteForwarding !== undefined && !['aurora', 'aurora-mysql'].includes(props.engine.engineType)) {
-      throw new Error(`\'enableLocalWriteForwarding\' is only supported for Aurora Mysql cluster engine type, got: ${props.engine.engineType}`);
-    }
-
     const enablePerformanceInsights = props.enablePerformanceInsights
       || props.performanceInsightRetention !== undefined || props.performanceInsightEncryptionKey !== undefined;
     if (enablePerformanceInsights && props.enablePerformanceInsights === false) {

packages/aws-cdk-lib/aws-rds/test/cluster.test.ts

@@ -177,7 +177,7 @@ describe('cluster new api', () => {
     });
 
     describe('enableLocalWriteForwarding', () => {
-      test('set enableLocalWriteForwarding', () => {
+      test('set enableLocalWriteForwarding for aurora mysql', () => {
         // GIVEN
         const stack = testStack();
         const vpc = new ec2.Vpc(stack, 'VPC');
@@ -197,20 +197,24 @@ describe('cluster new api', () => {
         });
       });
 
-      test.each([true, false])('throw error for enableLocalWriteForwarding with aurora postgresql cluster', (enableLocalWriteForwarding) => {
+      test('set enableLocalWriteForwarding for aurora postgresql', () => {
         // GIVEN
         const stack = testStack();
         const vpc = new ec2.Vpc(stack, 'VPC');
 
         // WHEN
-        expect(() => {
-          new DatabaseCluster(stack, 'Database', {
-            engine: DatabaseClusterEngine.auroraPostgres({ version: AuroraPostgresEngineVersion.VER_16_3 }),
-            vpc,
-            enableLocalWriteForwarding,
-            writer: ClusterInstance.serverlessV2('writer'),
-          });
-        }).toThrow('\'enableLocalWriteForwarding\' is only supported for Aurora Mysql cluster engine type, got: aurora-postgresql');
+        new DatabaseCluster(stack, 'Database', {
+          engine: DatabaseClusterEngine.auroraPostgres({ version: AuroraPostgresEngineVersion.VER_16_4 }),
+          vpc,
+          enableLocalWriteForwarding: true,
+          writer: ClusterInstance.serverlessV2('writer'),
+        });
+
+        // THEN
+        const template = Template.fromStack(stack);
+        template.hasResourceProperties('AWS::RDS::DBCluster', {
+          EnableLocalWriteForwarding: true,
+        });
       });
     });