Create python lambda layer using CDK

Question

How do I create a custom Lambda layer for python runtime using CDK?

Javascript CDK code for defining the lambda layer & function:

 this.sharedLayer = new lambda.LayerVersion(this, 'shared-layer', {
      code: lambda.Code.fromAsset('./lambda-functions/shared-layer'),
      compatibleRuntimes: [lambda.Runtime.PYTHON_3_8],
      layerVersionName: 'shared-layer',
    })
  }


this.testFunction = new lambda.Function(this, 'TestFunction', {
      runtime: lambda.Runtime.PYTHON_3_8,
      handler: 'function.lambda_handler',
      code: lambda.Code.fromAsset('./lambda-functions/test'),
      layers: [this.sharedLayer]
    })

The actual Lambda function contains a direct import of .py file in the shared-layer folder, like this:

import my_shared_functions

The Python layer folder in ./lambda-functions/shared-layer contains:

/---lambda-functions/
      /---shared-layer/
             boto3/
             my_shared_functions.py
             ...etc

Generate the template file:

cdk synth --no-staging my-lambda-stack > template.yml

Build and test locally using SAM:

sam build TestFunction && sam local invoke --profile siri-dev HeartbeatFunction

Error:

"Unable to import module 'function': No module named 'my_shared_functions'"

atlas_scoffed · Accepted Answer · 2022-07-21 03:42:24Z

2

Putting the lambda layer in a subfolder 'python' solved this issue:

/---lambda-functions/
      /---shared-layer/
            /---python/
                  boto3/
                  my_shared_functions.py
                  ...etc

I was running on the assumption that the folder structure for CDK was somehow different to uploading a layer manually.

answered Jul 21, 2022 at 3:42

atlas_scoffed

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1 Comment

Valera Over a year ago

Layer path for each runtime: docs.aws.amazon.com/lambda/latest/dg/…

Vikram S · Accepted Answer · 2022-07-21 05:23:21Z

1

if you are using CDK V2 use the @aws-cdk/aws-lambda-python-alpha package. Managing the python dependencies becomes easier using this package.

Please check below code, the aws-lambda-python-alpha uses the docker containers under hood to create the package.

import * as lambda from 'aws-cdk-lib/aws-lambda';
import * as pylambda from "@aws-cdk/aws-lambda-python-alpha";

const layerForCommonCode = new pylambda.PythonLayerVersion(
   this,
   "python-lambda-layer-for-common",
   {
     layerVersionName: "python-lambda-layer-for-common",
     entry: "../lambda-source/common-layer", 
     compatibleRuntimes: [lambda.Runtime.PYTHON_3_9],
   }
 );


The lambda-source structure as follows
--lambda-source
--common-layer
        --requirements.txt
          commonfiles.py

edited Jul 21, 2022 at 5:23

answered Jul 21, 2022 at 4:54

Vikram S

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1 Comment

atlas_scoffed Over a year ago

Thanks Vikram, I'm sure this will be helpful for some people. I'd use this construct if it wasn't still in Alpha. Strange how it's been moved to alpha in cdkv2, but not in v1.

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