MicroHack - Python serverless with Zappa.io

The context

I’ve visited one of the best conferences last september, Full Stack Fest in Barcelona. Since then, two talks are constantly in the back of my mind.

The first one is the talk by Ben Foxall (@benjaminbenben). He talked about Microhacks and how to become better in your experiments by constraining them. Write small reports / blogs of your Microhacks to so you have a nice overview of some of the experiments you’ve done. Guess what this blog is about..

The second talk I’m frequently think of was the talk by Rich Jones (@GUNdotIO) titled “Gone in 60 milliseconds: Offensive security in the serverless age”. A DDoS attack of slides, 452 in total. The talk main focus was about security and how you can hack the AWS infrastructure if things are not setup correctly. He knows his ways in AWS. That’s comes very handy if you want to build a cli which helps other people to run serverless python apps in the cloud. And this is exactly what he’s been doing with https://www.zappa.io.

What’s the experiment

I wanted to test the cli zappa.io with a simple python Flask app. The specs are simple: A service which reverses an input string running in the cloud with zappa.io. Serverless services are very interesting, because it’s based on lambdas and they typically run for a few milliseconds. So the costs are very low, utilization is very high. I’ve asked some colleagues to join me on a friday afternoon experiment and Jos Beijk wanted to help.

Let’s do it!

We need Python, a package manager (pip) and a tool to create isolated Python environments (Virtualenv). Store your AWS secrets in your .aws directory.

If you do not have an AWS account, don’t worry. Just signup and the first 1.000.000 requests per month are for free. https://aws.amazon.com/lambda/pricing

The experiment

GitHub: https://github.com/JeroenKnoops/zappa-string-reverser

What just happened?

The service

Create a simple Flask service which reverses an input string.

from flask import Flask, request

app = Flask(__name__)

@app.route('/<string:str>', methods=["GET"])
def reverse_str(str):
    return str[::-1]

if __name__ == '__main__':

Required libraries

Add required libraries Flask and Zappa in requirements.txt so pip can install it.


Install required libraries in virtual environment

Create a virtaul environment and activate it.

virtualenv venv
source venv/bin/activate.fish

Note: If you use zsh or bash you can use: source venv/bin/activate

pip install -r requirements.txt

Setup Zappa and deploy the service

Setup Zappa:

zappa init

Once you finish initialization, you’ll have a file named zappa_settings.json in your project directory defining your basic deployment settings.

Edit this file to add more service specific configurations:

    "dev": {
        "app_function": "string_reverser.app",
        "keep_warm": false,
        "debug": true,
        "log_level": "DEBUG",
        "aws_region": "eu-west-1",
        "profile_name": "default",
        "http_methods": ["GET"],
        "parameter_depth": 1,
        "timeout_seconds": 300,
        "memory_size": 128,
        "use_precompiled_packages": true,
        "s3_bucket": "zappa-<unique-thingy-goes-here>"

Deploy the app:

zappa deploy dev

The output is the url to our service. You see it’s https out-of-the-box.. :)

Test our service

The previous step will output an url to our service. In my case: https://z9cxt9gky6.execute-api.eu-west-1.amazonaws.com/dev/

Append the test string behind it and check the result.

curl https://z9cxt9gky6.execute-api.eu-west-1.amazonaws.com/dev/thisisateststring

Wiehoe! We got: gnirtstsetasisiht

Update the service

When you want to apply some changes, you can deploy it by running:

zappa update dev

If you add other libraries, make sure you add it in requirements.txt and install it locally in your virtual environment. All the packages in this folder will be shipped.


You can do various things with the zappa cli.

You can view logging for example:

zappa tail dev

See help for more info:

zappa --help

Feel free to check the created services in AWS console. You will see API gateway, CloudWatch and Lambdas.


Remove the infrastructure by simply undeploy the environment:

zappa undeploy dev


Ofcourse this example has no real value, but I wanted to see how it works. I think zappa.io is very good in its default values, but is extremely flexible. You don’t like the JSON format and prefer YAML or TOML? no problem. Want to run it in a VPC, no problem. Don’t like the Keeping The Server Warm settings, you can change it. Look at https://github.com/Miserlou/Zappa for the complete list of options. There’s good community support with a slack channel, so I would encourage you to look at this project. Especially because you have a lot of good defaults in this setup and this guy knows a few things about AWS.