Serverless Fast API

This is the second part of a two-part series on creating Serverless FAST API.

If you haven't checked the first part, do take a look here

Serverless Fast API

This is the first part of a two-part series on creating a serverless API using Fast API Fast API FastAPI is a modern, high-performance web framework for building APIs with Python based on standard type hints. It has the following key features: * Fast - Very high performance, on par with

The BitmaskersTirthankar Kundu

From our previous setup, we created a fast API application that does CRUD operation on Todos.

Now let us modify this a bit to support AWS serverless.

For this application, we will use AWS SAM.

I have already talked about serverless here for you to explore.

Updating the setup

We need to add a SAM template in order to let us deploy fast API to AWS Lambda. However, we also need an adapter that can translate AWS serverless events to be transferred to our Fast API server.

Enters Magnum!

We will use Magnum, an adapter for running ASGI applications in AWS Lambda to handle Function URL, API Gateway, ALB, and Lambda@Edge events.

This is how we configure the adapter

from mangum import Mangum

from app.main import app

handler = Mangum(app=app)

Now let's add the SAM Template

We will create a ProxyApi of type Serverless API.

The Runtime selected is python 3.8 and architecture is arm64
The proxy setup allows a pass-through of all API Calls to our fast API server using Magnum.

AWSTemplateFormatVersion: '2010-09-09'
Transform: AWS::Serverless-2016-10-31
Description: >
  fast-api

Globals:
  Function:
    Timeout: 30
    MemorySize: 128

Resources:
  ProxyApi:
    Type: AWS::Serverless::Api
    Properties:
      StageName: Prod
      BinaryMediaTypes: [ '*/*' ]

  HandlerFunction:
    Type: AWS::Serverless::Function
    Properties:
      Handler: handler.handler
      Runtime: python3.8
      Architectures:
        - arm64
      Events:
        FunctionProxy:
          Type: Api
          Properties:
            RestApiId: !Ref ProxyApi
            Path: "/{proxy+}"
            Method: ANY

Outputs:
  HandlerFunctionApi:
    Description: "API Gateway endpoint URL for Prod stage"
    Value: !Sub "https://${ProxyApi}.execute-api.${AWS::Region}.amazonaws.com/Prod/"
  HandlerFunction:
    Description: "Lambda Function ARN"
    Value: !GetAtt HandlerFunction.Arn
  HandlerFunctionIamRole:
    Description: "Implicit IAM Role created"
    Value: !GetAtt HandlerFunction.Arn

Deployment

Now all you need to do is run the below commands

sam build
sam deploy --guided

Once the deployment completes we can check in cloud formation, it should have an entry like the one below -

Now let us try the endpoints using Postman or any other rest client

Creating Todo

Fetching Todos

Deleting Todo

That's it! This completes our serverless Fast API! Hope you like it 🍻