aws_cdk.aws_ec2.InstanceType : Database instance type being synthesised into cloudformation incorrectly

[dnrico1]

Describe the bug

Defining instance_type=ec2.InstanceType("db.t4g.micro"), for a aws_rds.DatabaseInstance synths to "DBInstanceClass": "db.db.t4g.micro", causing the following error when deploying:
Resource handler returned message: "Invalid DB Instance class: db.db.t4g.micro (Service: Rds, Status Code: 400, Request ID: xxx)" (RequestToken: xxx HandlerErrorCode: InvalidRequest)

Expected Behavior

For the synth to be "DBInstanceClass": "db.t4g.micro", and the database to be created correctly

Current Behavior

Synth was "DBInstanceClass": "db.db.t4g.micro",

Reproduction Steps

1. Init an cdk app
2. Put the following into app.py:
   `
   from aws_cdk import (
   aws_rds as rds,
   aws_ec2 as ec2,
   )
   import aws_cdk as cdk
   from constructs import Construct

class StatefulStack(cdk.Stack):
def init(self, scope: Construct, id: str, **kwargs) -> None:
super().init(scope, id, **kwargs)

    # Define a VPC (minimal configuration for example purposes)
    vpc = ec2.Vpc(self, "MyVPC", max_azs=2)

    db_secret = rds.DatabaseSecret(self, "DBSecret",
        username="admin",
        secret_name="DBCredentials"
    )

    funnelsystems_database_name = "database"
    self.database = rds.DatabaseInstance(self, "database",
        engine=rds.DatabaseInstanceEngine.mysql(version=rds.MysqlEngineVersion.VER_8_0_28),
        instance_type=ec2.InstanceType("db.t4g.micro"),
        vpc=vpc,
        multi_az=False,
        allocated_storage=20, 
        database_name="name",
        publicly_accessible=False,
        credentials=rds.Credentials.from_secret(db_secret),

app = cdk.App()
StatefulStack(app, "StatefulStack")

app.synth()
3. Runcdk synth4. Check the synthesised cloudformation and noticeDBInstanceClass: db.db.t4g.micro`

Possible Solution

Unfortunately do not have enough experience with CDK / CFN to suggest a solution.

Additional Information/Context

No response

CDK CLI Version

2.114.1 (build 02bbb1d)

Framework Version

No response

Node.js Version

Node.js v20.5.1

OS

macOS Ventura 13.0

Language

Python

Language Version

No response

Other information

No response

[tim-finnigan]

Hi @dnrico1 thanks for reaching out. Have you tried just passing t4g.micro without the db.?

Here is the documentation for DatabaseInstance: https://docs.aws.amazon.com/cdk/api/v2/docs/aws-cdk-lib.aws_rds.DatabaseInstance.html. As noted there, the default for InstanceType is m5.large, so the db. appears to get added automatically.

Here is a list of DB instance classes supported in RDS: https://docs.aws.amazon.com/AmazonRDS/latest/UserGuide/Concepts.DBInstanceClass.html.

[pahud]

@dnrico1

You should remove the prefix db., the DatabaseInstance() construct will handle the prefixing for you.

aws-cdk/packages/aws-cdk-lib/aws-docdb/lib/instance.ts

Line 213 in b8b6baf

dbInstanceClass: `db.${props.instanceType}`,

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