Docker image to create Amazon Lambda packages

The usage of this tool changed a lot in April 2020. For the former usage, please check the branch legacy.

Why?

Some node and python modules require a build system because they contain c++ binding. Once deployed, the compiled module may not be compatible with the Amazon Lambda execution environment.

A common solution to this problem is to build the package on an EC2 instance using an Amazon Linux AMI and then to deploy it in Amazon Lambda. Building serverless applications, it is ironic to be forced to use an EC2 server to deploy code.

These docker images are based on the Amazon Linux image and contains libs required to install common python and NodeJS dependencies.

Using myrmex/lambda-packager docker images, you can avoid errors like these during execution in Amazon Lambda:

/var/lang/lib/libstdc++.so.6: version `GLIBCXX_3.4.21' not found (required by /var/task/node_modules/bcrypt/lib/binding/bcrypt_lib.node)

Module version mismatch. Expected 46, got 48.

Usage

You can use docker volumes to mount the code of the Lambda in a container and retrieve a generated zip archive. The directory where the source files must be mounted is /workspace/sources. The zip archive is generated in the /workspace/package directory in the container.

The generated zip archive can be used as an AWS Lambda deployment package. Check the examples in this repository.

Node.js

The default command of myrmex/lambda-packager:node-12 will install the dependencies defined in the package.json file.

docker run \
    -v `pwd`:/workspace/sources \
    -v /path/to/result/directory:/workspace/package \
    myrmex/lambda-packager:node-12

The archive /path/to/result/directory/package.zip can then be used as a Node.js Lambda package.

Python

The default command of myrmex/lambda-packager:python-3.8 will install the dependencies defined in the requirements.txt file.

docker run \
    -v `pwd`:/workspace/sources \
    -v /path/to/result/directory:/workspace/package \
    myrmex/lambda-packager:python-3.8

The archive /path/to/result/directory/package.zip can then be used as a python Lambda package.

Excluding files from the package

Before installing dependencies, the container copy the source files in a clean directory with rsync.

The environment variable RSYNC_OPTIONS allows to pass options for this rsync command. It is useful to exclude some files from the generated zip archive.

For Node.js the default value of RSYNC_OPTIONS is --exclude node_modules to enforce a clean installation.

For Python the default value of RSYNC_OPTIONS is --exclude venv --exclude .venv to avoid including useless virtual environnement in the zip archive.

example

If one also wants to exclude a docs directory and a README.md file for the generated archive, he can use the following command:

docker run \
    -e RSYNC_OPTIONS="--exclude node_modules --exclude docs --exclude README.md"
    -v `pwd`:/workspace/sources \
    -v /path/to/result/directory:/workspace/package \
    myrmex/lambda-packager:node-12

Working from inside a container

Depending on the context, one may want execute the packaging command from inside the container (eg: in a GitLab pipeline job).

Usage: package-lambda [path-to-sources-dir] [path-to-package-file]

The default value for path-to-sources-dir is /workspace/sources.

The default value for path-to-package-file is /workspace/package/package.zip.