AWS CDK - Multiple Stacks - Parameters for the location of Lambda Code is not found

Question

I'm using CDK to set up a CI/CD Pipeline. I have currently a code build from a git into the pipeline. There are then two builds - one that pulls out code for a lambda and builds an artifact for it, and a second that issues the cdk synth to construct the lambda framework (including a nested bucket and dynamo).

Then it heads to a deploy stage, but fails because it can't find the parameters for the location of the lambda code

ive been using this example: https://docs.aws.amazon.com/cdk/latest/guide/codepipeline_example.html

the only differences from this example are that I'm using python for all of it and due to known future needs, the lamdba's are are in a parallel directory from the stack code

|-Lambdas
|--Lambda1
|---Lambda1Code
|--Lambda2
|---Lambda2Code
|-CDKStacks
|--LambdaCreationStack
|--PipelineCreationStack
|--app.py

Everything runs up until deploy where it fails with the error "The following CloudFormation Parameters are missing a value:" and then lists the BucketName and ObjectKey

I assigned those as overrides as per the above link:

                                    admin_permissions=True,
                                    parameter_overrides=dict(
                                        lambda_code.assign(
                                            bucket_name=lambda_location.bucket_name,
                                            object_key=lambda_location.object_key,
                                            object_version=lambda_location.object_version
                                        )
                                    ),

as part of the pipeline actions CloudFormationCreateUpdateStackAction, and passed the code just like in the example from lambda stack to the pipeline stack. But every time the lambda stack is attempted to deploy the parameters for the location of the code 'do not exist'

I've tried overriding the parameters, but being in the pipeline and dynamically created I am hesitant to follow further (and my attempts didnt work anyways). I've tried a bunch of different stack/nested stack/single stack configurations but haven't had a Successs yet.

thoughts?

Answer 1

This basically boils down to CodeUri in the Cloudformation template will automatically append the s3 bucket if your CodeUri starts with ./

So you have 2 options.

1. In your pipeline output your artifact as normal, just do the whole repo from the codebuild into the code deploy. Your code deoploy can pick up the artifact naturally and will automatically append the S3 url to that

if you're using Python however, you MUST be aware that starting from a lambda directory deeper in the tree will mean that the python Imports expect that directory to be a root directory - meaning if you were in Lambdas/Lambda1 and wanted to import a file that existed in the Lambda1 directory, in order for it to work on AWS Lambda you would need to have the import be just the file name, ignoring the rest of the path.

This means that coding can be difficult, and running unit tests can be difficult as well. You'll want to add all the individual lambda folders (and their paths) from root to the PYTHONPATH env variable of your codebuild instance so the unit tests know where to do so (and add a .env file to your IDE as well to handle this in your local)

2. You use CDK and you cdk synth the stack you want to deploy. This creates a cdk.out folder with a bunch of asset zips in it plus the stack template (a json). you adjust your artifact output in the codebuild to output the cdk.out folder, and the asset zips are automatically (thanks to cdk) subbed into the codeUri locations in the also automatically synthed template. Once you know what the templates name is its easy to set the CodeDeploy to look for that template name and it will find the asset zips individually for each lambda.