lambdarado 0.1.0

Universal entry point for Docker images containing a WSGI app for the AWS Lambda.

Universal entry point for Docker images containing a Flask application for the AWS Lambda serverless platform.

Putting together:

• A web application written in Python that is compliant with the WSGI standard. Currently, only Flask is supported.
• A Docker image that contains the application code and dependencies
• AWS Lambda to run the code contained in the Docker image
• AWS API Gateway, that broadcasts web requests to and from your Lambda function

What it does

The package runs the relevant code depending on where it runs.

On the local computer, this is the debug server, serving requests to 127.0.0.1 right in the browser.

In the AWS cloud, this is the handler that passes Gateway requests to and from the WSGI application.

Install

$ pip3 install lambdarado 

Configure

Dockerfile:

FROM public.ecr.aws/lambda/python:3.8

# ... here should be the code that creates the image ...

ENTRYPOINT ["python", "main.py"]

main.py

import lambdarado import start

def get_app():
  # this method must return WSGI app, e.g. Flask
  from my_app_module import app
  return app 

start(get_app)

The main.py file will be imported twice when starting the server in AWS. The get_app method will only run once. Therefore, it is worth making sure that the application is initialized only when you call get_app.

Run

Local debug server

Running shell command on development machine:

$ python3 main.py

This will start Werkzeug server listening to http://127.0.0.1:5000.

Local debug server in Docker

Command-line:

$ docker run -p 6000:5000 docker-image-name

This will start Werkzeug server listening to http://0.0.0.0:5000 (inside the docker). The server is accessible as http://127.0.0.1:6000 from the host machine.

Production server on AWS Lambda

After deploying the same image as a Lambda function, it will serve the requests to the AWS Gateway with your app.

• You should connect the AWS Gateway to your Lambda function. For the function to receive all HTTP requests, you may need to redirect the /{proxy+} route to the function and make lambda:InvokeFunction policy less restrictive

Under the hood:

• The awslambdaric will receive requests from and send requests to the Lambda service
• The apig_wsgi will translate requests received by awslambdaric from the AWS Gateway. So your application doesn't have to handle calls from the gateway directly. For the application, requests will look like normal HTTP