[SOLVED] Lambdas on AWS with CloudFormation error:"A version for this Lambda function exists. Modify the function to create a new version."

Lambdas on AWS with CloudFormation error:"A version for this Lambda function exists. Modify the function to create a new version."

I'm deploying an AWS lambda using CloudFormation.

In the template I use the flag AutoPublishAlias: v1 which should create a version, add the necessary permissions, and update the alias "v1" to point to the latest version.

When I deploy this change, I get the following error:

A version for this Lambda function exists ( 8 ). Modify the function to create a new version.

I am using CICD. Sometimes I redeploy the same lambda having modified another part of the CloudFormation template (e.g adding the AutoPublishAlias flag).

I thought CloudFormation was supposed to be able to handle this correctly - only updating resources which have changed?

So why am I seeing this error, and is there a workaround other than introducing a dummy code change?

Solution

Please see https://seed.run/docs/serverless-errors/a-version-for-this-lambda-function-exists.html

The error is not Cloudformation, it's Serverless telling CF to deploy a new lambda version, which is in fact the same one.

I saw this issue after upgrading from sls 1 to 2. Had to do dummy changes for every function at once.

After that haven't seen the issue come up.