Fastapi: [Bug/Question] Response from the server is never received in case of using middleware.

Created on 23 Apr 2019 · 5Comments · Source: tiangolo/fastapi

Describe the bug
Response from the server is never received in case of using middleware.

To Reproduce
Steps to reproduce the behavior:

$ cat main.py

# !/usr/bin/env python
# -*- coding: utf-8 -*-
"""Entry point of the application."""


import logging

from fastapi import Depends, FastAPI, HTTPException
from pydantic import BaseModel
from starlette.middleware.base import BaseHTTPMiddleware
from starlette.requests import Request
from starlette.responses import Response

logger = logging.getLogger(__name__)


class AuthMiddleware(BaseHTTPMiddleware):
    async def dispatch(self, request, call_next):
        response = Response("Faled to authenticate", status_code=401)
        try:
            json = await request.json()
            request.state.is_authenticated = True
            logger.info(f"request.body: {json} ")
            response = await call_next(request)
        finally:
            request.state.is_authenticated = False
        return response


app = FastAPI(title="Nice Server",
              description="This is a very fancy project, with auto docs for the API and everything",
              version="0.1.0",
              docs_url="/docs", redoc_url=None)

app.add_middleware(AuthMiddleware)


class SomeTimestamp(BaseModel):
    ts: int


async def is_authenticated(request: Request):
    return request.state.is_authenticated


@app.post("/latest", response_model=SomeTimestamp, summary="Returning the latest ")
async def latest(*, some_timestamp: SomeTimestamp, is_authenticated: bool = Depends(is_authenticated)):
    logger.info(f"Let's see if this is authenticated: {is_authenticated}")
    if not is_authenticated:
        raise HTTPException(status_code=401, detail="Failed to verify the incoming token")

    logger.info(f"Received for prediction {some_timestamp.ts}")
    return some_timestamp.ts

Now run the server:

uvicorn main_server:app --reload

Now query this using curl:

curl --header "Content-Type: application/json" \
  --request POST \
  --data '{"ts":"123123"}' \
  http://127.0.0.1:8000/latest

Expected behavior
The server is stuck before sending response.

Screenshots
If applicable, add screenshots to help explain your problem.

Environment:

OS: [ Linux]
FastAPI Version [e.g. 0.18.0], get it with:

import fastapi
print(fastapi.__version__)

0.18.0

Python version, get it with:

python --version
3.7

Additional context
Add any other context about the problem here.

bug

Source

ansrivas

All 5 comments

Similar bug is encountered by @yihuang as well. Just the difference being accessing the json from the request body.
I wasn't sure earlier if this was an implementation issue on my side, but it seems this is happening in the form object as well.

@tiangolo any input would be much appreciated, thanks.

Reference issue:
https://github.com/tiangolo/fastapi/issues/191

ansrivas on 29 Apr 2019

I think this is a starlette problem(https://github.com/encode/starlette/issues/495).