(RDS): AuroraClusterInstance implement availabilityZone for provisioned instance type

[a-skuba]

Describe the feature

AuroraClusterInstance and ProvisionedClusterInstanceProps do not expose availability zone.

Use Case

We want to create multiple readers in specific availability zones.
We want to control, that each availability zone has at least one reader.

Proposed Solution

Add availabilityZone property to ProvisionedClusterInstanceProps and use it in AuroraClusterInstance when using ClusterInstance.provisioned() method.

Other Information

availabilityZone should be only used for InstanceType.PROVISIONED.

Acknowledgements

• I may be able to implement this feature request
• This feature might incur a breaking change

CDK version used

2.147.0

Environment details (OS name and version, etc.)

Any

[khushail]

@a-skuba ,Thanks for reaching out and submission of the FR.

[HannesBBR]

Hi, we have the same use case where we want to explicitly distribute our Aurora cluster instances over specific AZs (in our case both for serverless and provisioned instances).

FYI, our current workaround is to explicitly override the AZ property with something like this:

private spreadInstancesOverAzs(availabilityZones: string[]) {
    this.cluster.instanceIdentifiers.forEach((_, idx) => {
        const az = availabilityZones[idx % availabilityZones.length];
        const cfnDBInstance = this.cluster.node.tryFindChild(`instance-${idx + 1}`)?.node.defaultChild as CfnDBInstance;
        cfnDBInstance.availabilityZone = az;
    });
}