How to Log Raw HTTP Requests and Responses in Python FastAPI?

How to Log Raw HTTP Request/Response in Python FastAPI?

FastAPI provides several methods to capture and log raw HTTP requests and responses, catering to specific requirements and performance considerations.

Option 1: Middleware

Middleware allows you to intercept and process requests and responses. You can create a middleware that consumes the request body in a stream and stores it. For the response body, read it into a bytes object and return a custom Response. Use a BackgroundTask to log the data asynchronously to avoid impacting response time.

Example:

async def some_middleware(request: Request, call_next):
    req_body = await request.body()
    response = await call_next(request)
    res_body = b''
    async for chunk in response.body_iterator:
        res_body += chunk
    task = BackgroundTask(log_info, req_body, res_body)
    return Response(content=res_body, background=task)

Option 2: Custom APIRoute Class

Create a custom APIRoute class to manipulate the request and response bodies. This approach allows you to limit the logging to specific routes defined in an APIRouter.

Example:

class LoggingRoute(APIRoute):
    async def custom_route_handler(request: Request) -> Response:
        req_body = await request.body()
        response = await original_route_handler(request)
        res_body = b''
        async for item in response.body_iterator:
            res_body += item
        task = BackgroundTask(log_info, req_body, res_body)
        response = Response(content=res_body, background=task)
        return response

Consider the limitations of storing large request/response bodies in memory and use a BackgroundTask to avoid blocking request processing. If necessary, limit the logging to specific routes or exclude endpoints that return streaming responses.

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