Hi All, I need a feedback. We have many python services and needed to share codes between them. Now earlier i used to use gemfury to maintain a separate private python library, and use that via layers in our services, but it makes the development complex and extremely time consuming. As to test the new common code in cloud, i need to publish there, update layer and deploy services. (of course I can do some local invocations, but its exact same as cloud) Now after moving to seed, i am using deployment phases, in stage one, i have created a service called

layers

and inside that have a folder structure like this :

serviceA/
 - serverless.yml
 - requirements.txt
layers -
   - smiles/src/
   - smiles/setup.py
   - smiles/tests
   - serverless.yml
   - requierements.txt

Now in the

serviceA/requirements.txt

I refer the common code via this :

../layers/smiles

And it works in seed unittests. For local development, I do the following

cd layers/smiles
pip install -e.[dev]

Now i have seen if i mention

smiles

in side

layers/requirements.txt

then the

serverless-python-requirements

is unable to find the code. So after some research I found they have a vendor feature and I added like this :

custom:
  pythonRequirements:
    dockerizePip: non-linux
    layer: true
    name: ${self:provider.stage}-smiles-layer
    vendor: ./smiles/src

Now the layer can be created both locally and from seed cicd. now the final step is to attach the layer to the lambda.

serviceA

is deployed in later phase, so I thought i can export the layer arn and import it in

serviceA

via cloudformation imports. but it works in first deployment, but it does not work in further deployments due to this : https://gnomezgrave.com/2020/06/04/update-cross-stack-aws-lambda-layers/ So I use the layer like this :

layers:
      - !Sub arn:aws:lambda:ap-south-1:${AWS::AccountId}:layer:layers-${self:provider.stage}-python-requirements:latest

This solves my code sharing problems and the rules are easy to follow as per my opinion. Question is can it be simplified further ? or better approaches are available.

Hey @Sourav Sarkar, the simpliest way would be not to use layer. I’m not super familiar w/ Python, but can you import

smiles

directly in

serviceA

?