Aws-cdk: Creating Aurora Cluster with Postgresql fails

[vertti]

I expected that by just changing engine and engineVersion I would get a Postgresql Cluster.

Reproduction Steps

Running CDK with db-stack that contains:

    this.cluster = new DatabaseCluster(this, 'ProductDatabase', {
      defaultDatabaseName: 'ProductDb',
      engine: DatabaseClusterEngine.AURORA_POSTGRESQL,
      engineVersion: '11.4',
      masterUser: {
        username: 'clusteradmin',
      },
      instanceProps: {
        instanceType: InstanceType.of(InstanceClass.BURSTABLE2, InstanceSize.SMALL),
        vpcSubnets: {
          subnetType: SubnetType.ISOLATED,
        },
        vpc: props.vpc,
      },
    })

fails with:

The Parameter Group default.aurora5.6 with DBParameterGroupFamily aurora5.6 cannot be used for this instance. Please use a Parameter Group with DBParameterGroupFamily aurora-postgresql11 (Service: AmazonRDS; Status Code: 400; Error Code: InvalidParameterCombination; Request ID: 4ced8114-0f04-4659-9cde-c214db8638fa)

Clearly it's not supposed to pick aurora5.6 group family with postgresql11 but I have no idea what I'm doing wrong so I expect this to be a bug.

Error Log

  6/14 | 10:02:08 AM | CREATE_FAILED        | AWS::RDS::DBCluster                         | ProductDatabase (ProductDatabase9844B02C) The Parameter Group default.aurora5.6 with DBParameterGroupFamily aurora5.6 cannot be used for this instance. Please use a Parameter Group with DBParameterGroupFamily aurora-postgresql11 (Service: AmazonRDS; Status Code: 400; Error Code: InvalidParameterCombination; Request ID: 4ced8114-0f04-4659-9cde-c214db8638fa)
    new DatabaseCluster (/home/vertti/dev/kesko/k-ruoka-product-service/node_modules/@aws-cdk/aws-rds/lib/cluster.ts:315:21)
    \_ new ProductDbStack (/home/vertti/dev/kesko/k-ruoka-product-service/lib/db-stack.ts:17:20)
    \_ Object.<anonymous> (/home/vertti/dev/kesko/k-ruoka-product-service/bin/product-service.ts:11:17)
    \_ Module._compile (internal/modules/cjs/loader.js:778:30)
    \_ Module.m._compile (/home/vertti/dev/kesko/k-ruoka-product-service/node_modules/ts-node/src/index.ts:530:23)
    \_ Module._extensions..js (internal/modules/cjs/loader.js:789:10)
    \_ Object.require.extensions.(anonymous function) [as .ts] (/home/vertti/dev/kesko/k-ruoka-product-service/node_modules/ts-node/src/index.ts:533:12)
    \_ Module.load (internal/modules/cjs/loader.js:653:32)
    \_ tryModuleLoad (internal/modules/cjs/loader.js:593:12)
    \_ Function.Module._load (internal/modules/cjs/loader.js:585:3)
    \_ Function.Module.runMain (internal/modules/cjs/loader.js:831:12)

Environment

• CLI Version : 1.5.0
• Framework Version: 1.5.0
• OS : Ubuntu
• Language : Typescript

---

This is :bug: Bug Report

[vertti]

Adding the folllowing to the cluster definition:

 parameterGroup: ParameterGroup.fromParameterGroupName(this, 'ParameterGroup', 'default.aurora-postgresql11'),

gets you past the error message above. This should really by described in the documentation!

But after adding that I get a new error message:

RDS does not support creating a DB instance with the following combination: DBInstanceClass=db.t2.small, Engine=aurora-postgresql, EngineVersion=11.4, LicenseModel=postgresql-license. For supported combinations of instance class and database engine version, see the documentation. (Service: AmazonRDS; Status Code: 400; Error Code: InvalidParameterCombination; Request ID: dfb07895-5687-486e-a39e-49b0e59a170f)

From what I can find from AWS documentation, 11.4 is supported and db.t2.small is allowed for all Postgreqsql versions.

[vertti]

Finally found the correct table: according to this, Aurora Postgresql supports only t3.medium instances.

So I would add to the documentation:

• explanation on using the ParameterGroup for creating Postgresql
• link to the above tables to see what the instance types should be

[skinny85]

Thanks for reporting @vertti .

@jogold I wonder whether we can improve the DatabaseCluster (EDIT: actually, more DatabaseClusterEngine) construct, so that if parameterGroup was not specified, we will default it based on the engine that was passed - in this example, for instance, we see that the engine is AURORA_POSTGRESQL, and default the parameter group name to default.aurora-postgresql11. We can add a method to the DatabaseClusterEngine class to do that.

Thoughts?

[jogold]

@skinny85 related https://github.com/aws/aws-cdk/issues/2213 and https://github.com/aws/aws-cdk/issues/2512

The CFN doc: https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/aws-resource-rds-dbcluster.html#cfn-rds-dbcluster-dbclusterparametergroupname

If this argument is omitted, default.aurora5.6 is used. If default.aurora5.6 is used, specifying aurora-mysql or aurora-postgresql for the Engine property might result in an error.

So the right approach seems to be default.<engine><version> but version is optional, do you want to hard code default versions?

[skinny85]

So the right approach seems to be default. but version is optional, do you want to hard code default versions?

Yep. I think hard-coding is better in this case than failing at CFN deployment time.

[skinny85]

I flagged the wrong issues in #5721 , please ignore 🙂

[konstantinj]

fyi: I'm having the same issue + also the port is 3306 instead of 5432 when choosing DatabaseClusterEngine.AURORA_POSTGRESQL and adding the mentioned parameterGroup.