unable to provision postgres12 database cluster using the AWS CDK - postgresql

Question

given the following code:
// please note I created a wrapper around the cdk components, hence cdk.ec2 etc.
const vpc = new cdk.ec2.Vpc(this, `${appName}VPC`);
const dbCredentials = cdk.rds.Credentials.fromGeneratedSecret('postgres');
const engine = cdk.rds.DatabaseClusterEngine.auroraPostgres({ version: cdk.rds.PostgresEngineVersion.VER_12_6 });
const parameterGroup = cdk.rds.ParameterGroup.fromParameterGroupName(this, 'ParameterGroup', 'default.aurora-postgresql12');
// Create the Serverless Aurora DB cluster; set the engine to Postgres
const dbcluster = new cdk.rds.DatabaseCluster(this, `${appName}Cluster`, {
engine,
parameterGroup,
defaultDatabaseName: `${appName}DB`,
credentials: dbCredentials,
instanceProps: {
instanceType: cdk.ec2.InstanceType.of(cdk.ec2.InstanceClass.R5, cdk.ec2.InstanceSize.LARGE),
vpc,
vpcSubnets: {
subnetType: cdk.ec2.SubnetType.PUBLIC
},
publiclyAccessible: true,
scaling: { autoPause: cdk.core.Duration.seconds(600) } // Optional. If not set, then instance will pause after 5 minutes
}
});
Provided we use postgres11 - this code works without issue, when I try and install 12, I get the following error reported by the CDK:
The Parameter Group default.aurora-postgresql12 with DBParameterGroupFamily aurora-postgresql12 cannot be used for this instance. Please use a Paramet
er Group with DBParameterGroupFamily aurora-postgresql11 (Service: AmazonRDS; Status Code: 400; Error Code: InvalidParameterCombination; Request ID: e
e90210d-070d-4593-9564-813b6fd4e331; Proxy: null)
I have tried loads of combinations for instanceType (most of which work in the RDS UI on the console) - but I cannot seem to install postgres12 - any ideas what I am doing wrong?
tried this as well:
const vpc = new cdk.ec2.Vpc(this, `${appName}VPC`);
const dbCredentials = cdk.rds.Credentials.fromGeneratedSecret('postgres');
//DEFINING VERSION 12.6 FOR ENGINE
const engine = cdk.rds.DatabaseClusterEngine.auroraPostgres({ version: cdk.rds.PostgresEngineVersion.VER_12_6 });
//DEFINING 11 FOR PARAMETER GROUP
const parameterGroup = cdk.rds.ParameterGroup.fromParameterGroupName(this, 'ParameterGroup', 'default.aurora-postgresql11');
const dbcluster = new cdk.rds.DatabaseCluster(this, `${appName}Cluster`, {
engine,
parameterGroup,
defaultDatabaseName: `${appName}DB`,
credentials: dbCredentials,
instanceProps: {
instanceType: cdk.ec2.InstanceType.of(cdk.ec2.InstanceClass.R6G, cdk.ec2.InstanceSize.LARGE),
vpc,
vpcSubnets: {
subnetType: cdk.ec2.SubnetType.PUBLIC
},
publiclyAccessible: true,
scaling: { autoPause: cdk.core.Duration.seconds(600) } // Optional. If not set, then instance will pause after 5 minutes
}
});
works like a dream - but installs engine v11.9 :( - I need >12 because I need to install pg_partman
somewhere along the line the engine is not. being properly set - or is hardcoded to 11

Answer 1

This works for me:
const AURORA_POSTGRES_ENGINE_VERSION = AuroraPostgresEngineVersion.VER_10_7
const RDS_MAJOR_VERSION = AURORA_POSTGRES_ENGINE_VERSION.auroraPostgresMajorVersion.split('.')[0]
const parameterGroup = ParameterGroup.fromParameterGroupName(
scope,
`DBPrameterGroup`,
`default.aurora-postgresql${RDS_MAJOR_VERSION}`,
)
new ServerlessCluster(scope, `Aurora${id}`, {
engine: DatabaseClusterEngine.auroraPostgres({
version: AURORA_POSTGRES_ENGINE_VERSION,
}),
parameterGroup,
defaultDatabaseName: DATABASE_NAME,
credentials: {
username: 'x',
},
vpc: this.vpc,
vpcSubnets: this.subnetSelection,
securityGroups: [securityGroup],
})