FastAPI Deployment to AWS Lambda with Serverless Framework

Deploy FastAPI to AWS Lambda using Serverless Framework

Hello, I will share how to deploy your FastAPI Project to the AWS Lambda Function. Let's do it…

Table of Contents

• Create FastAPI Project or you can use the existing one
• Create AWS Execution Role for Lambda
• Serverless Framework Configurations
• Deploy the project

Create FastAPI Project

If you are using the existing FastAPI Project, just skip this.
Ops, dont forget to install mangum as the requirements

Start with creating the project directory anywhere do you want on your machine, then create the python virtual environment in it.

mkdir FastAPI-Lambda-Function
cd FastAPI-Lambda-Function
python3 -m venv venv
source venv/bin/activate

Then install the requirements that are FastAPI, and Mangum

• FastAPI (fastapi.tiangolo.com)
• Mangum (mangum.io)

pip install fastapi mangum uvicorn

• Uvicorn (uvicorn.org) we need this to test the project locally

then, create a file named main.py

# main.py
import os
from fastapi import FastAPI
from mangum import Mangum

STAGE = os.environ.get('STAGE')
root_path = '/' if not STAGE else f'/{STAGE}'
app = FastAPI(title="FastAPI x AWS Lambda", root_path=root_path)
@app.get('/hello')
def hello_api(name: str = "World"):
    return {"hello": name}
# Mangum Handler, this is so important
handler = Mangum(app)

Let’s run the project,

uvicorn main:app --reload

The FastAPI Documentation (Swagger)

Create AWS Execution Role for Lambda

Creating an execution role in the IAM console

By default, Lambda creates an execution role with minimal permissions when you create a function in the Lambda console. You can also create an execution role in the IAM console.

To create an execution role in the IAM console

• Open the Roles page in the IAM console.
• Choose Create role.
• Under Common use cases, choose Lambda.

Create Role for Lambda

• Choose Next: Permissions.
• Under Attach permissions policies, choose the AWS managed policies AWSLambdaBasicExecutionRole and AWSXRayDaemonWriteAccess.
• Choose Next: Tags.
• Choose Next: Review.

Review Lambda Execution Role Creation

• For Role name, enter lambda-execution-role.
• Choose Create role.

Open the role that you just created, then copy the Role ARN (will be used on the next step)

AWS Role Detail

Serverless Framework Configurations

create Python Requirements file

pip freeze > requirements.txt

Install serverless framework if it's not installed before

npm i -g serverless

Install serverless-python-requirements plugin for serverless

sls plugin install -n serverless-python-requirements

then, create the serverless.yaml file

# serverless.yaml
service: FastAPI-Lambda-Function

package:
  individually: true

provider:
  name: aws
  profile: ${opt:aws-profile, "default"}
  region: ${opt:region}
  stage: ${opt:stage, "dev"}
  runtime: python3.8
  memorySize: 128
  timeout: 30
  iam:
    role: ${opt:iamrole}
plugins:
  - serverless-python-requirements

custom:
  pythonRequirements:
    dockerizePip: true
    layer:
      name: FastAPI-Lambda-Function
      description: FastAPI-Lambda-Function API Layer
      compatibleRuntimes:
        - python3.8
functions:
  app:
    package:
      patterns:
        - 'src/**'
        - '!requirements.txt'
        - '!package.json'
        - '!package-lock.json'
        - '!.serverless/**'
        - '!venv/**'
        - '!node_modules/**'
      handler: main.handler
      environment:
        STAGE: ${self:provider.stage}
      layers:
        - { Ref: PythonRequirementsLambdaLayer }
      events:
        - http:
            method: get
            path: /
        - http:
            method: any
            path: /{proxy+}

Deploy the project

Make sure you already configure the AWS CLI Before, because the deployment process will be using it.

serverless deploy --region 'ap-southeast-1' --stage 'dev' --aws-profile 'default' --iamrole 'paste-your-lambda-arn-role-here'

Change the opt value with your own

• region: the AWS region that you wanna used
• aws-profile: the AWS CLI Profile (default will be used if it's not provided)
• stage: the default is dev, but you could change it with do you want (ex: staging)
• iamrole: using the ARN Role that you are copied on the previous step

If the deployment process success, the output on the console will be like the following picture

Deploy FastAPI on the AWS Lambda Success

Then open the docs URL on the browser

Deploy FastAPI on the AWS Lambda

Done 🎉🎉🎉

Project Repo: https://github.com/dwisulfahnur/fastapi-mangum-lambda