[aws-redshift] Single-node clusters fail with node count error

[Mejato]

Issue

Unable to deploy a single node Redshift cluster using the high level 'Cluster' construct.

Reproduction Steps

class RedshiftStack(core.Stack):

    def __init__(self, scope: core.Construct, id: str, **kwargs) -> None:
        super().__init__(scope, id, **kwargs)

        # Define a VPC
        my_vpc = ec2.Vpc(self, id='my-vpc', cidr='10.0.0.0/16', enable_dns_hostnames=True, enable_dns_support=True)

        # Define a Redshift cluster
        my_redshift_cluster = redshift.Cluster(self, id='my-redshift-cluster', master_user=redshift.Login(master_username='username'), vpc=my_vpc, cluster_type=redshift.ClusterType.SINGLE_NODE)

What did you expect to happen?

A successful deployment of a basic 1 node Redshift cluster.

What actually happened?

Error with deployment.

8:09:58 PM | CREATE_FAILED | AWS::Redshift::Cluster | my-redshift-cluster
Number of nodes must be not be supplied for cluster type single-node. (Service: AmazonRedshift; Status Code: 400; Error Code: InvalidParameterValue; Request ID: 57b21bf4-0b33-4b60-a6c1-4bdada5ed268)

Environment

• CLI Version : aws-cdk@1.60.0
• Framework Version: 1.60.0
• Node.js Version: v12.18.3
• OS : Ubuntu 20.04.1 LTS
• Language (Version): Python 3.8.2

Suggestion

https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/aws-resource-redshift-cluster.html#cfn-redshift-cluster-clustertype

ClusterType

The type of the cluster. When cluster type is specified as

    single-node, the NumberOfNodes parameter is not required.

    multi-node, the NumberOfNodes parameter is required.

Valid Values: multi-node | single-node

Default: multi-node 

NumberOfNodes

The number of compute nodes in the cluster. This parameter is required when the ClusterType parameter is specified as multi-node.

For information about determining how many nodes you need, go to Working with Clusters in the Amazon Redshift Cluster Management Guide.

If you don't specify this parameter, you get a single-node cluster. When requesting a multi-node cluster, you must specify the number of nodes that you want in the cluster. 

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This is 🐛 Bug Report

[njlynch]

Thanks for the bug report, @Mejato.

It looks like we are explicitly setting the node count here to 1, rather than letting it remained undefined if the node type is single-node.

aws-cdk/packages/@aws-cdk/aws-redshift/lib/cluster.ts

Line 428 in 132f2b2

const nodeCount = props.numberOfNodes !== undefined ? props.numberOfNodes : (clusterType === ClusterType.MULTI_NODE ? 2 : 1);

The fix would be to only set the nodeCount explicitly for MULTI_NODE setups. Bonus would be to validate it's either unset or 1 if SINGLE_NODE, and unset it if set to 1.