Error: DBClusterInstanceClass isn't supported for DB engine aurora-mysql | Cloudformation

Question

Hello Team,

I have created a CloudFormation template for aurora-mysql8.0. But while running the template I am getting error: **DBClusterInstanceClass isn't supported for DB engine aurora-mysql**. I am not sure if I need to remove this option from the template as I wont be able to to set the DBClusterInstance type then.

The template is as below:

```
Parameters:
  DatabaseName:
    Default: MyDatabase
    Description: The database name
    Type: String
    MinLength: '1'
    MaxLength: '64'
    AllowedPattern: '[a-zA-Z][a-zA-Z0-9]*'
    ConstraintDescription: must begin with a letter and contain only alphanumeric
      characters.
  DBUser:
    NoEcho: 'false'
    Description: The database admin account username
    Type: String
    MinLength: '1'
    MaxLength: '16'
  DBPassword:
    NoEcho: 'true'
    Description: The database admin account password
    Type: String
    MinLength: '8'
    MaxLength: '41'
  DBClusterInstanceClass: 
    Description: Instance class for RDS
    Type: String
    MinLength: '1'
    MaxLength: '16'
  AllocatedStorage:
    Description: Required storage
    Type: Number
  Engine:
    Description: DB Engine
    Type: String
    Default: aurora-mysql
    MinLength: '1'
    MaxLength: '16'
  EngineVersion:
    Description: RDS version
    Type: String
    Default: 8.0.mysql_aurora.3.02.1
  BackupRetentionPeriod:
    Description: RDS retention period
    Type: String
  DBClusterIdentifier:
    Description: DB identifier
    Type: String
  BackupRetentionPeriod:
    Description: RDS retention period
    Type: String
  EnablePerformanceInsights:
    Description: Enable or Disable performance insight
    Type: String
  PreferredBackupWindow:
    Description: Backup window
    Type: String
  PreferredMaintenanceWindow:
    Description: Maintainence window
    Type: String
  VpcSecurityGroupIds:
    Description: SG for RDS
    Type: String
  SubnetID1:
    Description: Subnets for the RDS in subnet group
    Type: String
  SubnetID2:
    Description: Subnets for the RDS in subnet group
    Type: String
  MonitoringRoleArn:
    Description: RDS Monitoring Role
    Type: String
Resources:
  MyDB:
    Type: AWS::RDS::DBCluster
    Properties:
      DatabaseName: !Ref 'DatabaseName'
      AllocatedStorage: !Ref 'AllocatedStorage'
      DBClusterInstanceClass: !Ref 'DBClusterInstanceClass'
      Engine: !Ref 'Engine'
      EngineVersion: !Ref 'EngineVersion'
      BackupRetentionPeriod: !Ref 'BackupRetentionPeriod'
      DBClusterIdentifier: !Ref 'DBClusterIdentifier'
      DBSubnetGroupName: !Ref 'MYSubnetGroup'
      EnableCloudwatchLogsExports: 
         - audit
         - error
      PerformanceInsightsEnabled: !Ref 'EnablePerformanceInsights'
      PreferredBackupWindow: !Ref 'PreferredBackupWindow'
      PreferredMaintenanceWindow: !Ref 'PreferredMaintenanceWindow'
      PubliclyAccessible: False
      StorageEncrypted: True
      StorageType: gp2
      MonitoringInterval: 60
      MonitoringRoleArn: !Ref 'MonitoringRoleArn'
      VpcSecurityGroupIds: 
        - !Ref 'VpcSecurityGroupIds'
      MasterUsername: !Ref 'DBUser'
      MasterUserPassword: !Ref 'DBPassword'
      DBClusterParameterGroupName: !Ref 'ClusterParameterGroup'
      DeletionProtection: True
      AutoMinorVersionUpgrade: True
      CopyTagsToSnapshot: True
  ClusterParameterGroup:
    Type: 'AWS::RDS::DBClusterParameterGroup'
    Properties:
      Description: Cluster Parameter group for RDS
      Family: aurora-mysql8.0
      Parameters:
        require_secure_transport: 'ON'
        server_audit_logging: '1'
  MYSubnetGroup:
    Type: AWS::RDS::DBSubnetGroup
    Properties: 
      DBSubnetGroupDescription: subnet group for the rds
      SubnetIds: 
        - !Ref 'SubnetID1'
        - !Ref 'SubnetID2'
```

Accepted Answer

For DB engine `aurora-mysql`, you should use a combination of CloudFormation resource types `AWS::RDS::DBCluster` and `AWS::RDS::DBInstance`. Then, you specify the instance type via `DBInstanceClass` property of `AWS::RDS::DBInstance`.

The AWS CloudFormation documentation has some examples on creating an Aurora DB: [https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/aws-resource-rds-dbcluster.html#cfn-rds-dbcluster-dbclusterinstanceclass](https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/aws-resource-rds-dbcluster.html#cfn-rds-dbcluster-dbclusterinstanceclass). It's using `aurora-postgresql`, but you can use it as reference when creating your `aurora-mysql`.

Answer

Thank you for your question.

`StorageType` only apply for RDS, and RDS Multi-AZ cluster(not Aurora).

To create Aurora cluster, and instances, please use two separate section like below code snippet. This is minimum snippet, and reference purpose only. So please add necessary section, and settings as you want.

```yaml
Resources:
  DBCluster:
    Type: AWS::RDS::DBCluster
    DeletionPolicy: Snapshot
    Properties:
      Engine: aurora-mysql
      EngineVersion: 8.0.mysql_aurora.3.02.1

DBInstance1:
    Type: AWS::RDS::DBInstance
    Properties:
      Engine: aurora-mysql
      DBClusterIdentifier: !Ref "DBCluster"
      DBInstanceClass: !Ref "DBClusterInstanceClass"
      DBSubnetGroupName: !Ref "DBSubnetGroup"
      DBParameterGroupName: !Ref "DBParameterGroup"
```

I hope this might help.

Answer

Hi! You can use the below command to determine db instance classes supported in a region based on engine and engine-version.
`aws rds describe-orderable-db-instance-options --engine aurora-mysql --engine-version 8.0.mysql_aurora.3.02.1 --query "OrderableDBInstanceOptions[].{DBInstanceClass:DBInstanceClass,SupportedEngineModes:SupportedEngineModes[0]}" --output table `

Error: DBClusterInstanceClass isn't supported for DB engine aurora-mysql | Cloudformation

Thanks Rares. I tried that but it gave the same error. However later I found that we need to use io1 storage type instead of gp2 for multiaz and we need to add iops parameter as well.

Update requires: No interruption

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