Creating an AWS Lambda Layer using CloudShell

2021, Feb 15    

Using python packages from pip is a bit nontrivial on AWS Lambda. The solution is to use Lambda Layers, which act like virtual environments. Creating a layer programatically isn’t straightforward, but it can be done.

A layer can be created by zipping packages downloaded from pip, but they must be compiled for use on Amazon Linux. One simple way to do that without spinning up an EC2 instance is with AWS CloudShell.

First, virtualenv must be installed on the CloudShell environment.

sudo pip install virtualenv

Without sudo, pip install yields an error PermissionError: [Errno 13] Permission denied: '/usr/local/lib64/python3.7/site-packages/...'. Not sure why.

It’s also a good idea to set alias pip=pip3. Somehow this isn’t the default on CloudShell.

Given a file requirements.txt, the script below can be run on CloudShell to produce a file that is sufficient for Python 3.7, the installed Python version on CloudShell at the time of writing.

virtualenv ve
source ve/bin/activate
pip install -r requirements.txt
mkdir -p tmp/python
cp -rp ve/lib/python3.7/site-packages/* tmp/python
cp -rp ve/lib64/python3.7/site-packages/* tmp/python
pushd tmp
pushd python
rm -r *.dist-info *.virtualenv
zip -r9 -q ../ python
rm -r tmp ve