How to add middleware in different places?

[mht2953658596]

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Example Code

from fastapi import FastAPI, Request, Depends
app = FastAPI()
app.add_middleware(
	CORSMiddleware,
	allow_origins=["*"],
	allow_credentials=False,
	allow_methods=["*"],
	allow_headers=["*"],
)


from fastapi import Request, Response
import time

from main import app


@app.middleware("http")
async def add_process_time_header(request: Request, call_next):
	start_time = time.time()
	response = await call_next(request)
	process_time = time.time() - start_time
	response.headers["X-Process-Time"] = str(process_time)
	return response

Description

I've noticed that middleware functions in FastAPI need to be in the same .py file as the code containing app = FastAPI() in order for the middleware function to work.

in main.py:

from fastapi import FastAPI, Request, Depends
app = FastAPI()
app.add_middleware(
	CORSMiddleware,
	allow_origins=["*"],
	allow_credentials=False,
	allow_methods=["*"],
	allow_headers=["*"],
)

This cross-origin middleware is effective.

However, I created a directory named "middleware" at the same level as the main.py, and inside that directory, there's a file named "demo_middleware.py".
The directory structure is as follows:
-main.py
-middleware
--init.py
--demo_middleware.py

in demo_middleware.py

from fastapi import Request, Response
import time

from main import app


@app.middleware("http")
async def add_process_time_header(request: Request, call_next):
	start_time = time.time()
	response = await call_next(request)
	process_time = time.time() - start_time
	response.headers["X-Process-Time"] = str(process_time)
	return response

However, this middleware function for measuring time isn't functioning.

Operating System

Windows

Operating System Details

No response

FastAPI Version

0.100.0

Pydantic Version

1.10.7

Python Version

Python 3.8.16

Additional Context

No response

[vedil]

you can manually like you mentioned for CORS some like app.add_middleware(demo_middleware.Timer)

you can follow #397 to get more idea

[YuriiMotov]

Remove from main import app and @app.middleware("http") from demo_middleware module, then import your middleware to the main module and add middleware to the stack using

app.middleware("http")(demo_middleware.add_process_time_header)

or

app.add_middleware(BaseHTTPMiddleware, dispatch=demo_middleware.add_process_time_header)

Another way is to convert your middleware into the pure ASGI middleware and add it using app.add_middleware(YourMiddlewareClass)