aws_lambda: regular deploys fail after hotswap

[samchungy]

Describe the bug

After deploying a lambda version with --hotswap, when you attempt to run a regular cdk deploy with the same changes it fails with the following error message:

Resource handler returned message: "Version already exists: [arn:aws:lambda:ap-southeast-2:572093383043:function:serviceName:96]. Please modify the function to create a new version. (Service: Lambda, Status Code: 409, Request ID: aa44dd2b-8347-4e8a-996e-408a52e648ec)" (RequestToken: 0af5f624-50e3-8943-96d4-16687d2fe1fb, HandlerErrorCode: AlreadyExists)

Expected Behavior

Regular cdk deploy succeeds after a hotswap deploy

Current Behavior

cdk deploy fails.

Reproduction Steps

https://github.com/samchungy/cdk-lambda-hotswap-bug

run ENVIRONMENT=dev yarn deploy

    const worker = new aws_lambda_nodejs.NodejsFunction(this, 'worker', {
      architecture: aws_lambda.Architecture.ARM_64,
      runtime: aws_lambda.Runtime.NODEJS_20_X,
      entry: './src/app.ts',
      timeout: Duration.seconds(30),
      bundling: defaultWorkerBundlingConfig,
      functionName: 'serviceName',
      environment: {
        ...defaultWorkerEnvironment,
        ...context.workerLambda.environment,
      },
    });

Run --hotswap followed by deploy without

Possible Solution

I assume this is failing because the function configuration hasn't changed between a hotswap deploy and a regular deploy. So when CF goes to sync up and the version configuration is the same it fails

My workaround at the moment is adding a dynamic description which means that the Lambda has to be deployed fresh with every deploy.

This may just have to be an accepted quirk, but perhaps some documentation around this would be great

Additional Information/Context

No response

CDK CLI Version

2.110.0

Framework Version

No response

Node.js Version

20

OS

Mac OSX

Language

TypeScript

Language Version

No response

Other information

No response

[samchungy]

Hey @khushail I've added a repo to reproduce

[pahud]

Yes I think this is expected and should be documented.

What's happening with hotswap with lambda version is that it essentially bump the lambda version with SDK call and this causes the drift. When you cdk deploy, CFN tries to bump the original version hence conflict.

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[samchungy]

Yeah cool, it makes sense.

It's quite difficult to work with this from a CI POV. Ideally, my master build should never just suddenly break. So I think the dynamic description would be the best workaround for using hotswap.