From 23f69a56fe3842e8d8e3c811e6635cd9f8255eb0 Mon Sep 17 00:00:00 2001
From: BLasan <benuraab@gmail.com>
Date: Thu, 25 Mar 2021 14:35:03 +0530
Subject: [PATCH] fix(rds): fail with a descriptive error if Clusters instance
 count is a deploy-time value fixes #13558

---
 packages/@aws-cdk/aws-rds/lib/cluster.ts      |  3 +++
 .../@aws-cdk/aws-rds/test/cluster.test.ts     | 20 +++++++++++++++++++
 2 files changed, 23 insertions(+)

diff --git a/packages/@aws-cdk/aws-rds/lib/cluster.ts b/packages/@aws-cdk/aws-rds/lib/cluster.ts
index a3f06555afdb9..24bb5944b8a85 100644
--- a/packages/@aws-cdk/aws-rds/lib/cluster.ts
+++ b/packages/@aws-cdk/aws-rds/lib/cluster.ts
@@ -651,6 +651,9 @@ interface InstanceConfig {
  */
 function createInstances(cluster: DatabaseClusterNew, props: DatabaseClusterBaseProps, subnetGroup: ISubnetGroup): InstanceConfig {
   const instanceCount = props.instances != null ? props.instances : 2;
+  if (Token.isUnresolved(instanceCount)) {
+    throw new Error('The number of instances a RDS Cluster consists of cannot be provided as a deploy-time only value!');
+  }
   if (instanceCount < 1) {
     throw new Error('At least one instance is required');
   }
diff --git a/packages/@aws-cdk/aws-rds/test/cluster.test.ts b/packages/@aws-cdk/aws-rds/test/cluster.test.ts
index 74f538be5d998..80c2603973a25 100644
--- a/packages/@aws-cdk/aws-rds/test/cluster.test.ts
+++ b/packages/@aws-cdk/aws-rds/test/cluster.test.ts
@@ -54,6 +54,15 @@ describe('cluster', () => {
 
   });
 
+  test('check instanceCount is a token', () => {
+    const stack = testStack();
+    const vpc = new ec2.Vpc(stack, 'VPC');
+    expect(() => {
+      createRDSCluster(stack, vpc);
+    }).toThrow('The number of instances a RDS Cluster consists of cannot be provided as a deploy-time only value!');
+
+  });
+
   test('can create a cluster with a single instance', () => {
     // GIVEN
     const stack = testStack();
@@ -1959,3 +1968,14 @@ function testStack(app?: cdk.App) {
   stack.node.setContext('availability-zones:12345:us-test-1', ['us-test-1a', 'us-test-1b']);
   return stack;
 }
+
+function createRDSCluster(stack: any, vpc: any) {
+  new DatabaseCluster(stack, 'Database', {
+    instances: cdk.Token.asNumber('1'),
+    engine: DatabaseClusterEngine.AURORA,
+    instanceProps: {
+      instanceType: ec2.InstanceType.of(ec2.InstanceClass.BURSTABLE2, ec2.InstanceSize.SMALL),
+      vpc,
+    },
+  });
+}