NeptuneDatabase spins up RDS Aurora MySQL by default

[adam-imeson]

New user! This is all using TypeScript.

Tried to follow the Neptune example. Got an RDS cluster running Aurora instead:

I think that this happened because of line 123 here. Should read engine: rds.DatabaseClusterEngine.Neptune, if the DatabaseClusterEngine enum works the way I think it does.

As a workaround, I tried creating the cluster as an RDS object like so:

        const database = new rds.DatabaseCluster(this, 'NeptuneCluster', {
            engine: rds.DatabaseClusterEngine.Neptune,
            instanceProps: {
                instanceType: new ec2.InstanceTypePair(ec2.InstanceClass.Burstable2, ec2.InstanceSize.Small),
                vpc,
                vpcPlacement: { 
                    subnetsToUse: ec2.SubnetType.Public,
                }
            },
            masterUser: {
                username: dbUsername.value.toString(),
                password: dbPassword.value.toString()
            }
        });

This transpiled just fine. cdk diff showed that the old instances would be destroyed and new ones would be stood up, as expected, but CloudFormation bounced it during deployment with the following message:

[ 4/14] Fri Sep 28 2018 19:04:36 GMT+0000 (UTC)  CREATE_FAILED       [AWS::RDS::DBCluster] NeptuneCluster7FC72740 The parameter MasterUsername is not valid for engine: neptune (Service: AmazonRDS; Status Code: 400; Error Code: InvalidParameterValue; Request ID: 33ef806c-ffe4-4a06-80df-7bcf83e0a76e)
NeptuneCluster7FC72740 was created at: /NeptuneDatabase/NeptuneCluster/Resource
        new DatabaseCluster (/home/ec2-user/environment/graph-database-cdk/node_modules/@aws-cdk/aws-rds/lib/cluster.js:34:25)
        \_ new NeptuneDB (/home/ec2-user/environment/graph-database-cdk/dboptions/neptune.js:21:26)
        \_ new GraphDatabaseApp (/home/ec2-user/environment/graph-database-cdk/index.js:8:9)
        \_ Object.<anonymous> (/home/ec2-user/environment/graph-database-cdk/index.js:11:22)
        \_ Module._compile (module.js:653:30)
        \_ Object.Module._extensions..js (module.js:664:10)
        \_ Module.load (module.js:566:32)
        \_ tryModuleLoad (module.js:506:12)
        \_ Function.Module._load (module.js:498:3)
        \_ Function.Module.runMain (module.js:694:10)
        \_ startup (bootstrap_node.js:204:16)
        \_ bootstrap_node.js:625:3

I tried removing the masterUser block and also just removing the username and password fields in the block, but in both cases the code wouldn't transpile:

dboptions/neptune.ts:24:74 - error TS2345: Argument of type '{ engine: DatabaseClusterEngine.Neptune; instanceProps: { instanceType: InstanceTypePair; vpc: VpcNetwork; vpcPlacement: { subnetsToUse: SubnetType.Public; }; }; }' is not assignable to parameter of type 'DatabaseClusterProps'.
  Property 'masterUser' is missing in type '{ engine: DatabaseClusterEngine.Neptune; instanceProps: { instanceType: InstanceTypePair; vpc: VpcNetwork; vpcPlacement: { subnetsToUse: SubnetType.Public; }; }; }'.

 24         const database = new rds.DatabaseCluster(this, 'NeptuneCluster', {
                                                                             ~
 25             engine: rds.DatabaseClusterEngine.Neptune,
    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
... 
 36 //            }
    ~~~~~~~~~~~~~~~
 37         });
    ~~~~~~~~~

dboptions/neptune.ts:24:74 - error TS2345: Argument of type '{ engine: DatabaseClusterEngine.Neptune; instanceProps: { instanceType: InstanceTypePair; vpc: VpcNetwork; vpcPlacement: { subnetsToUse: SubnetType.Public; }; }; masterUser: {}; }' is not assignable to parameter of type 'DatabaseClusterProps'.
  Types of property 'masterUser' are incompatible.
    Type '{}' is not assignable to type 'Login'.
      Property 'username' is missing in type '{}'.

 24         const database = new rds.DatabaseCluster(this, 'NeptuneCluster', {
                                                                             ~
 25             engine: rds.DatabaseClusterEngine.Neptune,
    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
... 
 36             }
    ~~~~~~~~~~~~~
 37         });
    ~~~~~~~~~

Theory: Neptune doesn't expect a username/password, but the CDK expects Neptune to expect a username/password.

[rix0rrr]

Good diagnosis, thanks for the report 😊.

Honestly, the Neptune module is an untested unsupported proof of concept. We might need to remove it.