shallot

A serverless service for publishing AWS layers. Shallot manages packages in Poetry, then packages them as a layer published publicly to AWS. Use this service to publish layers and make them accessible by other services.

The current form of the Poetry settings in pyproject.toml is set to install pandas and sagemaker. Manual edits (described below) were used to remove numpy and scipy, so that this layer paired well with a published scipy+numpy layer (arn:aws:lambda:us-east-1:668099181075:layer:AWSLambda-Python37-SciPy1x:2).

Intro to Lambda Layers in Python describes how to use a separate Serverless package to publish a layer to AWS, which you can then import in other packages.

serverless-python-requirements contains installation instructions for the plugin, including details about Poetry support.

Poetry integration is broken somewhere, such that the serverless-python-requirements function for ignoring particular packages (noDeploy) doesn't work. Therefore, we have to manually delete packages from the deployment .zip package before deploying the layer to AWS.

Instructions

After setting up a new directory with direnv, poetry, and serverless boilerplate...

1. poetry self:update --preview. This brings poetry up to v1.0, which supports the export command.
2. sls plugin install -n serverless-python-requirements
3. poetry add <all your dependencies>
4. poetry update
5. poetry install
6. poetry export --without-hashes -f requirements.txt > requirements.txt. Note that this requirements.txt file is deleted every time you run sls package, so you'll have call this command frequently.
7. Make sure that Docker is running.
8. sls package. This creates the .serverless folder and package all the dependencies from requirements.txt into a .zip file called pythonRequirements.zip.
9. cd .serverless
10. unzip pythonRequirements.zip. This unzips into a folder called python.
11. Delete whatever packages you don't want from inside the python folder, including their .dist-info files.
12. rm pythonRequirements.zip
13. zip -r pythonRequirements.zip python
14. cd ..
15. sls deploy --package .serverless. This deploys without re-packaging, using instead the .zip file you just created.

At the end of this deployment, Serverless releases the ARN of your new Lambda Layer.