Understanding When and How one can Implement FastAPI Middleware (Examples and Use Instances) | by Mike Huls | Dec, 2024

Supercharge Your FastAPI with Middleware: Sensible Use Instances and Examples

Middleware sits between an API router its routes, performing as a layer the place you’ll be able to run code earlier than and after a request is dealt with. On this article we’ll discover two key use instances of middleware in FastAPI, demonstrating each how it really works and why it’s helpful. Let’s code!

To start, let’s create a easy API that serves as a base for our middleware examples. The app beneath has just one route: take a look at which simulates precise work by sleeping for a couple of milliseconds earlier than returning “OK”.

import random
import time
from fastapi import FastAPI
app = FastAPI(title="My API")
@app.get('/take a look at')
def test_route() -> str:
sleep_seconds:float = random.randrange(10, 100) / 100
time.sleep(sleep_seconds)
return "OK"

What’s middleware?

Middleware acts as a filter between the incoming HTTP request and the processing finished by your software. Consider it like airport safety: each passenger should undergo safety earlier than and after boarding the airplane. Equally, each API request passes by means of middleware: each earlier than being dealt with…