Create and publish python lambda layer using bash

README.md

Summary

This is a bash script I wrote to quickly create a python 3.7 layer on AWS.

The first part creates a zip file.

The trick to create a correct zip file for python lambda layers is to ensure the unzipped file has a directory structure like

python/lib/python3.7/site-packages/

and the actual package(s) is within site-packages folder. Otherwise lambda code gives an error like

{
  "errorMessage": "Unable to import module 'lambda_function': No module named 'requests'",
  "errorType": "Runtime.ImportModuleError"
}

Unfortunately, AWS documentation isn't very explicit about this.

The second part publishes the layer on to AWS using aws cli.

Assumptions

1. This was created on a mac running python 3.7 but should work on linux also.
2. AWS cli is installed and properly configured.

create_python_layer.sh

#!/bin/bash

# prepare zip file for lambda layers

# if [ ! -n "$1" ]
# then
#   echo "Usage: `basename $0` package_name"
#   exit 1
# fi  

# Inputs
package="package_name"
runtime="python3.7"
description="details about package like ver no"
# aws cli related inputs
AWS_REGION="us-east-1"
AWS_PROFILE="profilename"


cwd=$(pwd)
mkdir -p "$package/python/lib/$runtime/site-packages"
cd "$package/python/lib/$runtime/site-packages"

# install package to the site-packages directory
pip install "$package" -t .

cd $cwd/$package

zip -r "$package.zip" python

aws lambda publish-layer-version \
  --layer-name $package \
  --description $description \
  --compatible-runtimes $runtime \
  --zip-file fileb://$package.zip \
  --region $AWS_REGION \
  --profile $AWS_PROFILE

cd $cwd

Line 29 gives this error which can be fixed by adding mkdir python just before 29.
zip warning: name not matched: python