Cannot update serverless aurora maxCapacity with CfnDBCluster

If you create a serverless Aurora database with CfnDBCluster, and then try to update the maxCapacity, the deployment fails with the message: "DatabaseCluster You currently can’t modify EndpointPort with Aurora Serverless. (Service: AmazonRDS; Status Code: 400; Error Code: InvalidParameterCombination; " Even though the port was not changed.

Reproduction Steps

Create a serverless database:

  const dbCluster = new rds.CfnDBCluster(this, "DatabaseCluster", {
          engine: "aurora-postgresql",
          engineMode: "serverless",
          engineVersion: "10.7",
          masterUsername: 'postgres',
          databaseName: "collab",
          masterUserPassword: "Foobar",
          dbSubnetGroupName: new rds.CfnDBSubnetGroup(this, "CollabDbSubnetGroup", {
              dbSubnetGroupDescription: ` Collab Db cluster subnet group`,
              subnetIds: vpc.selectSubnets({subnetType: ec2.SubnetType.PRIVATE}).subnetIds
          }).ref,
          vpcSecurityGroupIds: [mySecurityGroupId],
          storageEncrypted: true,
          backupRetentionPeriod: 35,
          deletionProtection: false,
          port: 5432,
          scalingConfiguration: {
              autoPause: true,
              secondsUntilAutoPause: 300,
              minCapacity: 2,
              maxCapacity: 2
          }
      });

Deploy this.

Change nothing other than maxCapacity (to 4). Running cdk diff shows:

Stack TestCollabDbStack
Resources
[~] AWS::RDS::DBCluster DatabaseCluster DatabaseCluster
 └─ [~] ScalingConfiguration
     └─ [~] .MaxCapacity:
         ├─ [-] 2
         └─ [+] 4

Which is what you’d expect. However, if you run cdk deploy, the following happens:

TestCollabDbStack
TestCollabDbStack: deploying...
TestCollabDbStack: creating CloudFormation changeset...
 0/2 | 11:45:35 PM | UPDATE_IN_PROGRESS   | AWS::RDS::DBCluster     | DatabaseCluster
 1/2 | 11:45:36 PM | UPDATE_FAILED        | AWS::RDS::DBCluster     | DatabaseCluster You currently can't modify EndpointPort with Aurora Serverless. (Service: AmazonRDS; Status Code: 400; Error Code: InvalidParameterCombination; Request ID: 83490936-5bdf-418e-b065-7a79a176beea)

Environment

• CLI Version :
• Framework Version: 1.15.0
• OS : Windows 10
• Language : Typescript

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This is 🐛 Bug Report

[vendamere]

Ran into this issue as well. The solution or at least work-around, if you’re not using a custom port, is to just omit the port from the template. It’s optional and will use the default port for the engine specified and won’t be seen as a change.

[chris-bateman]

Had the same issue. Removing the port reference worked. I have submitted this as a bug report to AWS via our paid support account. My suggestion to both the CDK and RDS team would be to make bug reports available to all users when they can’t be escalated on the appropriate repo.

Ran into this issue as well. The solution or at least work-around, if you’re not using a custom port, is to just omit the port from the template. It’s optional and will use the default port for the engine specified and won’t be seen as a change.