python 3.9 Flask serverless lambda

Sample Serverless framework using API gateway that calls a lambda with python 3.9 with Flask.

prerequisites

Setup the prerequisites:

• python3 and virtualenv
• nodejs: https://nodejs.org/en/download/
• servless framework:

npm install -g serverless

setup and use a virtualenv

See also: https://www.infoworld.com/article/3239675/virtualenv-and-venv-python-virtual-environments-explained.html

• setup a new virtualenv:

virtualenv venv -p python3

• activate the virtualenv (unix / macos):

. venv/bin/activate

or on Windows using the Command Prompt:

venv\Scripts\activate.bat

setup flask support for lambda on serverless framework

install (in the virtual env) the dependencies:

pip install Flask
pip freeze > requirements.txt

sls plugin install -n serverless-wsgi
sls plugin install -n serverless-python-requirements

first time setup for serverless framework to work

on aws create a IAM user for programmatic access: https://www.serverless.com/framework/docs/providers/aws/guide/credentials/

change service name of the new api

Change service name 'hello-world-lambda' in serverless.yml file with a new name.

local development (on port 5050)

python app.py

Using Lambda custom url for direct access the lambda without api gateway

Using this new functionality will remove the max timeout of 30s from API Gateway. If you want instead use an API GW, comment those lines and uncomment the lines above in serverless.yml.

# 1 - Enable direct Lambda Function URL, this can bypass API Gateway 30s timeout
   url:
     # Allow CORS for all requests from any origin
     cors: true

See also: https://www.serverless.com/blog/aws-lambda-function-urls-with-serverless-framework#:~:text=Unlike%20API%20Gateway%2C%20Function%20URLs,(up%20to%2015%20minutes).

Using Lambda through an api gateway

This will have max 30s timeout and more configuration options available. Uncomment those lines in serverless.yml:

# 2 - Enable lambda through API Gateway HTTP API. Note, using API Gateway will force a 30s max timeout
   # on all endpoints
   #events:
   #  - httpApi: '*'

test sample endpoints

curl  http://localhost:5050/ -H 'Content-Type: application/json' 
curl  http://localhost:5050/quote -H 'Content-Type: application/json' 
curl -X POST http://localhost:5050/testpost -H 'Content-Type: application/json' -d '{"message":"this is a test!"}'

DEPLOY to AWS

export AWS_ACCESS_KEY_ID=<your-key-here>
export AWS_SECRET_ACCESS_KEY=<your-secret-key-here>
sls deploy

or in windows:

SET AWS_ACCESS_KEY_ID=<your-key-here>
SET AWS_SECRET_ACCESS_KEY=<your-secret-key-here>
sls deploy

after some seconds it should prints an AWS api gateway url like this:

https://XXXXXXX.execute-api.us-east-1.amazonaws.com/

now you can access your flask apis like GET 'https://XXXXXXX.execute-api.us-east-1.amazonaws.com/quote'!