custom-resource: Passthrough physicalResourceId when its not specified in onUpdate at AwsCustomResource

[konokenj]

Describe the feature

Currently, when using AwsCustomResource construct, users have to specify physicalResourceId in onUpdate.
This limitation is brought by AwsCustomResource copies onUpdate (physicalResourceId is NOT mandatory) to onCreate (physicalResourceId is mandatory) when onCreate is not specified.

AwsCustomResource should be able to omit physicalResourceId in onUpdate with passthrough it from request. This is useful when users want to call an update API without resoure replacing.

Some AWS APIs send empty response in update. This causes problem in below situation:

• Create API generates unpredictable IDs, and return it in response
  • Users set physicalResourceId: PhysicalResourceId.fromResponse()
• Update API requires resource ID (not Name), and return empty response
  • Users provide resouce ID by new PhysicalResourceIdReference() in parameters
  • With empty response, users can't use physicalResourceId: PhysicalResourceId.fromResponse() or any ID generation

Use Case

To create / update / delete resources that is not covered by CloudFormation. If API specification matches above conditions, this feature is critical. Like below:

• https://docs.aws.amazon.com/athena/latest/APIReference/API_UpdateNotebook.html
• https://docs.aws.amazon.com/singlesignon/latest/IdentityStoreAPIReference/API_UpdateUser.html

Proposed Solution

Passthrough physicalResourceId from request to response in onUpdate when physicalResourceId is not specified.
To do that, update input check logic for physicalResourceId.

This change is not breaking, because it's not a problem if users can specify physicalResourceId in onUpdate.

onCreate	onCreate.physicalResourceId	onUpdate	onUpdate.physicalResourceId	validation error now?	validation error after change?
AwsSdkCall	specified	AwsSdkCall	specified	no	no
AwsSdkCall	specified	AwsSdkCall	undefined	yes	no <-
AwsSdkCall	undefined	AwsSdkCall	undefined	yes	yes
AwsSdkCall	undefined	AwsSdkCall	specified	yes	yes
undefined (copied from onUpdate)	undefined	AwsSdkCall	specified	no	no
undefined (copied from onUpdate)	undefined	AwsSdkCall	undefined	yes	yes
AwsSdkCall	specified	undefined	undefined	no	no
AwsSdkCall	undefined	undefined	undefined	yes	yes

Other Information

Instead of omit physicalResourceId to passthrough, we can provide a property like passthroughPhysicalResourceId: true. But I think its more intuitive that omit physicalResourceId.

Acknowledgements

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

CDK version used

2.61.1

Environment details (OS name and version, etc.)

Node.js 16.13.0, MacOS 12.6.2

[khushail]

Hi @konokenj , thanks for reaching out. It would be great if you could provide some more information on what you are trying to solve and the solution steps as well. Thanks.

[konokenj]

Hi @khushail, thank you for your ownership.
The handler function is implemented to return from event object if PhysicalResourceId is unspecified, so I simply change Construct's error checking.

aws-cdk/packages/@aws-cdk/custom-resources/lib/aws-custom-resource/runtime/index.ts

Line 153 in 9b2a45a

physicalResourceId = event.ResourceProperties[event.RequestType]?.physicalResourceId?.id ?? event.PhysicalResourceId;

I created a PR.
#24194

[github-actions]

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