[Solved] You wrote this middleware but it does not run for any requests:class MyMiddleware: async def dispatch(self, request, call_next):... | FastAPI

FastAPI - Middleware and Hooks

You wrote this middleware but it does not run for any requests:

class MyMiddleware:
    async def dispatch(self, request, call_next):
        print("Middleware active")
        response = await call_next(request)
        return response

app = FastAPI()
app.add_middleware(MyMiddleware)

What is the likely problem?

AMiddleware must be added after route definitions

Bdispatch method should be synchronous

CMyMiddleware does not inherit from BaseHTTPMiddleware

DMiddleware class must be decorated with @middleware

Step-by-Step Solution

Solution:

Step 1: Check middleware class inheritance
FastAPI middleware classes must inherit from BaseHTTPMiddleware or implement ASGI interface properly.
Step 2: Identify missing inheritance
MyMiddleware lacks inheritance, so FastAPI cannot use it as middleware.
Final Answer:
MyMiddleware does not inherit from BaseHTTPMiddleware -> Option C
Quick Check:
Middleware must inherit BaseHTTPMiddleware [OK]

Quick Trick: Middleware class must inherit BaseHTTPMiddleware [OK]

Common Mistakes:

MISTAKES

Making dispatch synchronous instead of async
Adding middleware before routes (order usually doesn't block)
Thinking @middleware decorator is required for class middleware

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More FastAPI Quizzes

You wrote this middleware but it does not run for any requests:

Step 1: Check middleware class inheritance

Step 2: Identify missing inheritance

Final Answer:

Quick Check:

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