(aws-tools): CLI --hotswap -> We don't support attributes of the 'AWS::DynamoDB::Table' resource

[kbakk]

What is the problem?

When using nested stacks, and a DynamoDB table is created in the parent stack, --hotswap will not work.

Reproduction Steps

Python reproducer

Initialize project with cdk init sample-app --language python and create/change:

app.py

import aws_cdk as cdk

from cdk_py_workshop.cdk_py_workshop_stack import ApiStack, DatabaseStack


app = cdk.App()
parent = DatabaseStack(app, "cdk-py-workshop-database")
ApiStack(parent, "cdk-py-workshop-api", table=parent.table)

app.synth()

cdk_py_workshop/cdk_py_workshop_stack.py

from constructs import Construct
from aws_cdk import (
    Stack,
    NestedStack,
    aws_lambda as _lambda,
    aws_apigateway as apigw,
    aws_dynamodb as ddb
)

class DatabaseStack(Stack):
    def __init__(self, scope: Construct, id: str, **kwargs) -> None:
        super().__init__(scope, id, **kwargs)
        self.table = ddb.Table(
            self, 'Hits',
            partition_key={'name': 'path', 'type': ddb.AttributeType.STRING}
        )

class ApiStack(NestedStack):

    def __init__(self, scope: Construct, id: str, table, **kwargs) -> None:
        super().__init__(scope, id, **kwargs)
        my_lambda = _lambda.Function(
            self, 'HelloHandler',
            runtime=_lambda.Runtime.PYTHON_3_7,
            code=_lambda.Code.from_asset('lambda'),
            handler='hello.handler',
            environment={"TABLE": table.table_name}
        )
        table.grant_read_write_data(my_lambda)
        apigw.LambdaRestApi(
            self, 'Endpoint',
            handler=my_lambda,
        )

lambda/hello.py

def handler(event, context):
    print(f'request: {event}')

Run cdk deploy once, then modify lambda/hello.py (e.g. add another print). Try to run cdk deploy --hotswap.

What did you expect to happen?

Super fast hotswap of my lambda function and an output like ✨ Total time: 10.97s (or less 🤩 )

What actually happened?

I'm getting this message:

✨  Synthesis time: 7.16s

⚠️ The --hotswap flag deliberately introduces CloudFormation drift to speed up deployments
⚠️ It should only be used for development - never use it for your production Stacks!
cdk-py-workshop-database: deploying...
[ ... removed ... ]
Could not perform a hotswap deployment, because the CloudFormation template could not be resolved: We don't support attributes of the 'AWS::DynamoDB::Table' resource. This is a CDK limitation. Please report it at https://github.com/aws/aws-cdk/issues/new/choose
Falling back to doing a full deployment
cdk-py-workshop-database: creating CloudFormation changeset...

 ✅  cdk-py-workshop-database

✨  Deployment time: 70.7s

Stack ARN:
arn:aws:cloudformation:eu-west-1:012345678900:stack/cdk-py-workshop-database/fc7aeb10-a530-11ec-81af-0a3d49828e3b

✨  Total time: 77.86s

And CDK runs a full deployment.

CDK CLI Version

2.16.0 (build 4c77925)

Framework Version

No response

Node.js Version

v16.14.0

OS

Debian GNU/Linux 11

Language

Python

Language Version

Python 3.9.10

Other information

No response

[ryparker]

Hey @kbakk 👋🏻

Thanks for opening this issue. I'm going to convert this into a feature-request seeing as we currently don't support Hot swapping with Dynamo DB.

Currently hot swapping supports Lambda functions, Step Functions state machines, and Amazon ECS container images.

CDK CLI docs

However this issue will be used to track this request and collect community interest. We use +1s to help us prioritize our work, and as always we are happy to take contributions if anyone is interested to pick this up and submit a PR (please make sure to follow our contribution guidelines.) 🙏

[hoegertn]

What attributes of a table should be hotswappable? I am afraid we might open Pandora's box if we allow hotswapping for too many resources.

[matmeylan]

What do you think of allowing developers to still use hotswapp for resources that are hot swappable (lambda, ecs, etc), even if there is not supported resources in the stack ?

Hear me out:

In our case for instance, the need for hotswap is quite high. Full deployments take ~10 minutes. Hotswapping would reduce dev deployments dramatically, hence increase our DX tremendously. But, because we're using RDS (same problem as for Dynamo users), we can't use hotswapp. But, I'd be more than happy to use hotswapp without RDS support. I could always use a full deployment when I need to update the DB.

[skinny85]

@kbakk thanks for opening the issue. Can you actually show your CDK code, and the exact command you are executing to trigger the hotswap deployment?

Thanks,
Adam

[kbakk]

@skinny85 Hi, did you see the expandable section "Python reproduce" in the description? Is there anything in addition that's wanted here?

[skinny85]

@skinny85 Hi, did you see the expandable section "Python reproduce" in the description?

I in fact did not see it 😃. Thanks, I think that's all I need!

[skinny85]

I was able to reproduce this - working on a fix!

[github-actions]

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