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Lightweight docker image for running, testing, packaging and deploying python-based AWS lambda functions

• Docker:python-lambda
• GitHub:python-lambda-docker
• Based on thepython-lambda library bynficano

I needed a Docker-based environment in which to host AWS python lambda functions for the purpose of testing and building them... python-lambda works well under virtualenv for development, but build and deployment automation require a clean and reproducible environment to operate in. Our CI system already supported Docker as a containerization system, so it was the obvious choice.

In order to use this, you will have your project derive its own Dockerfile based on a base python-lambda image corresponding to which version of Python you wish to run.

An example of a usable project can be found in theexample/ directory. The lambda function inservice.py takes a JSON input file like the one provided inevent.json and returns an ASCII-art version of the text described in it. TheDockerfile derives from python-lambda as a base image, and loading the example directory contents into the image at the path/lambda, then installs dependencies from therequirements.txt file.

To build a docker image from the providedexample/ calledexample-lambda-image with the ASCII-art lambda function in it, run:

$ cd example/$ docker build --tag example-lambda-image .

Any time you make changes to the example project, you'll need to re-run thedocker build command above, or you can investigate using docker volumes to sync local filesystem changes into the container.

The exampleDockerfile uses a:latest docker tag in the FROM line, which is currently the same as:3.6, but if you wish to use a different Python version you can change this. Supported Python versions are 2.7 and 3.6. To use Python version 2.7 change the first line of the exampleDockerfile to:

FROM kilna/python-lambda:2.7

You will also need to change the following line inconfig.yaml

runtime: python2.7

If you want to execute the lambda function against theevent.json input file:

$ docker run example-lambda-image lambda invoke _  _     _ _                        _    _ _| || |___| | |___    __ __ _____ _ _| |__| | || __ / -_) | / _ \_  \ V  V / _ \ '_| / _` |_||_||_\___|_|_\___( )  \_/\_/\___/_| |_\__,_(_)                 |/

If you would like to build the lambda function (which will package the function and all its dependencies), run:

$ docker run example-lambda-image lambda build

The result will be a zip file created in the /lambda/dist directory inside the container.

If you would like to build andtest the lambda function and gather up the results, you can run:

$ docker run example-lambda-image lambda_build_tar | tar -x -vbuild.logtest.logdist/dist/2017-09-01-003647-example-lambda.zip

Behind the scenes, what this does is:

• Removes any log and dist files from prior runs
• Executes 'lambda build' and stores the log in/lambda/build.log in the container
• If present and executable, runs/lambda/run_tests and stores the log in /lambda/test.log in the container
• Tars the log files, and the contents of the dist directory in /lambda on the container and pipes it to standard output
• Untars the contents bundled up within the container, and extracts them into your current directory

You can deploy your lambda function to Amazon's infrastructure... you'll need to add AWS credentials into theconfig.yaml file. Alternately, if your local AWS CLI environment is working, you can add a.aws/ directory (you cancp ~/.aws) into theexample/ directory), then re-build your image. Once AWS is working within your container, you can then run the following to deploy your function to Amazon:

$ docker run example-lambda-image lambda deploy