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(cfnSpec): Attributes returned as integers output dummy values instead of calling getAtt

See original GitHub issue

What is the problem?

I can’t make output value from attrClusterEndpointPort property of memorydb.CfnCluster. The generated CloudFormation template show hardcoded number value rather than reference value from AWS::MemoryDB::Cluster resource.

  "Outputs": {
    "MemoryDBEndpointAddress": {
      "Value": {
        "Fn::GetAtt": [
    "MemoryDBEndpointPort": {
      "Value": "-1.888154589708829e+289"

Reproduction Steps

import { Stack, StackProps, CfnOutput } from 'aws-cdk-lib';
import { Construct } from 'constructs';
import * as ec2 from 'aws-cdk-lib/aws-ec2';
import * as iam from 'aws-cdk-lib/aws-iam';
import * as memorydb from 'aws-cdk-lib/aws-memorydb';
import * as elasticache from 'aws-cdk-lib/aws-elasticache';

export class BenchmarkVsElasticacheRedisStack extends Stack {
  constructor(scope: Construct, id: string, props?: StackProps) {
    super(scope, id, props);

    const vpc = new ec2.Vpc(this, 'VPC');

    const dbSecurityGroup = new ec2.SecurityGroup(this, 'DB Security Group', {

    const subnets = vpc.selectSubnets({
      subnetType: ec2.SubnetType.PRIVATE_WITH_NAT

    const memoryDBSubnetGroup = new memorydb.CfnSubnetGroup(this, 'MemoryDB Subnet Group', {
      subnetGroupName: 'memorydb-test-subnet-group',
      subnetIds: subnets.subnetIds,

    const memoryDBCluster = new memorydb.CfnCluster(this, 'Memory DB Cluster', {
      clusterName: 'memorydb-test',
      nodeType: 'db.r6g.large',
      aclName: 'open-access',
      subnetGroupName: memoryDBSubnetGroup.subnetGroupName,
      securityGroupIds: [ dbSecurityGroup.securityGroupId ],
      tlsEnabled: false
    memoryDBCluster.node.addDependency(memoryDBSubnetGroup, dbSecurityGroup);

    new CfnOutput(this, 'Memory DB Endpoint Address', {
      value: memoryDBCluster.attrClusterEndpointAddress
    new CfnOutput(this, 'Memory DB Endpoint Port', {
      value: memoryDBCluster.attrClusterEndpointPort.toString()

What did you expect to happen?

The output value of memorydb cluster’s port number should be the reference of the resource.

What actually happened?

The output value of memorydb cluster’s port number is hardcoded number value.

CDK CLI Version

2.3.0 (build beaa5b2)

Framework Version


Node.js Version






Language Version

TypeScript (3.9.10)

Other information

No response

Issue Analytics

  • State:closed
  • Created 2 years ago
  • Reactions:1
  • Comments:6 (4 by maintainers)

github_iconTop GitHub Comments

peterwoodworthcommented, Jan 6, 2022

Thanks for reporting this @naxxster, I’m finding the same behavior with the other attributes which end up as integers. (Such as Lightsail::Disk.Iops)

Before this is fixed, you can create the getAtt reference with the Fn.getAtt() function.

Fn.getAtt('MyCluster', 'ClusterEndpoint.Port')
github-actions[bot]commented, Jul 1, 2022


Comments on closed issues are hard for our team to see. If you need more assistance, please either tag a team member or open a new issue that references this one. If you wish to keep having a conversation with other community members under this issue feel free to do so.

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