Question 107948 in Amazon Web Sevices Question posted in
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Amazon web services – Create python lambda layer using CDK

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'"
Tags:

2

Answers


  1. Chosen as BEST ANSWER
    0

    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.


  2. 0

    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
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