Python Serverless Microservices Nilo Ney Coutinho Menezes ([email protected]) 

Serverless Application Framework • Written in Javascript, but works with multiple languages • Uses Node, Python and Chocolatey (alternative Windows Package Manager) • Deploys the serverless infrastructure in the cloud. Compatible with Amazon Web Services, Google Cloud, Microsoft Azure and others • Simplifies configuration and application updates • Configuration files written in YAML • https://www.serverless.com/ 

Server less? • We know the server still there • But we don’t have to keep it running • We don’t have to update it frequently • We can have more as we need them (autoscaling) • We only pay if we use them • So, it is an industry term to say somebody else is taking care of the server for you. 

Microservices • Microservices are an architecture for development and deployment of new systems • It antagonizes the traditional monolithic architecture that deploys the full system in a single application • Microservices means we should split our systems into smaller ones • Smaller parts are easy to understand, can be deployed independently • Share no database with other parts • Share data and services via a well-defined API • Can be rewritten one by one (less coupling) 

Lambdas • Lambdas are Functions as a Service (FaaS) provided by Amazon Web Services (AWS) • We will be using AWS as our example provider • You need to have an account to test the code shown in this presentation • You can create a free account on their web site: https://aws.amazon.com/es • If it is your first time on AWS, I strongly suggest you check their web site and documentation, as you will be paying for the resources used beyond the free tier. • To start using AWS with Python, install their command-line client: pip install awscli 

Python Serverless Microservices • Because we use Python • Because we use AWS Lambdas, FaaS, serverless • And we would divide each API call in a different lambda, grouped in a domain, following the directives of Microservices and Domain-Driven Design (DDD). Check these books for more info: 

Installing • Download and install node.js from https://nodejs.org/en/ • Install the Serverless Application Framework: npm install –g serverless • Let’s created the application stub type: serverless • Try to answer the questions as in the image below: 

The stub application: handler.py 

Serverless.yaml • This is all the configuration we need for our simple function. • It says we are going to deploy a Python 3.8 Lambda Function • It defines the handler (the module and function name) • It also specifies the URL path to use and the http method 

Deploying 

Visiting our new page • Go to : • https://977optmvi2.execute-api.us-east-1.amazonaws.com/dev/pycones2020/hello • Or • http://bit.ly/PyConES2020-Serverless 

The super user friendly page 

What is in this json? • In the input field, all parameters passed to your function • Copy and paste it to your preferred text editor that supports JSON. Reformat the code to make it easier to read. • You get user location with IP and country information • The URL and path used on this call • Any parameter used (query string and path) if any • You can access all these values as in simple python dictionary 

What do we have now API Gate way Browser Lambda Hello 

Wait, no huge framework? • Nope • You have a very simple function deployed to the cloud • You choose the batteries • You can combine multiple Python libraries depending on your needs • Leverage the cloud provider services like databases, api gateways, queues, etc 

Advantages • Simple, you can read the function from top to bottom, no hidden magic code • Cheap, millions of invocations for less than 1 euro • Pays as you go (no upfront costs, if you don’t use, you won’t pay either) • Functions can be deployed independently • No downtime, old version keeps running until the new one is deployed 

Disadvantages • As any new thing can be difficult at the beginning • You get dependent to a cloud provider • More tools to use • Lack of framework to start with 

What’s next • Create a DynamoDB table • Add more functions • Play with AWS Cognito to support authenticated users • Read about lambda layers • Check serverless-python-requirements, a serverless plugin to create dependencies packages for Python • Other frameworks to help with Lambdas and Python:  AWS Chalice https://github.com/aws/chalice  AWS SAM https://aws.amazon.com/serverless/sam/ 

Thank you • If you have any questions, do not hesitate to contact me: [email protected] • You can also visit my book’s website (Python for Beginners): https://librodepython.com/ • See you later this year on Python Brasil and Python Sweden