This repo contains the minimum necessary code to reproduce a bug(see fastapi/fastapi#5141) with fastAPI upload, in which sending multiple paralel requests to an endpoint using uploadFile causes some requests to hang, as in they don't complete nor error out.
This repo constains a docker-compose and Dockerfile, and can be used with VSCode's devcontainer.
clone the repo: git clone git@github.com:guites/fast-api-upload-issue.git
Using VS Code's devcontainer:
- Open the directory with VS Code.
- Click on View -> Command Palette and select "Dev Containers: Reopen in Container"
- install dependencies
pip3 install -r requirements.txt - start the server by running
python3 main.py
Using Docker:
- Build an image from the Dockerfile:
docker build . -t bug-repro-fastapi - Run that image, mapping to a port:
docker run -p 8000:8000 bug-repro-fastapi
Then, access http://localhost:8000 and, using the file input, select a file bigger than ~60kb. The javascript code will automatically attempt to POST the file 100 times to the file upload endpoint, which will cause the hanging.
To check that the bug is indeed happening, open the developer tools' networking tab before starting the uploads:
You can then verify the error on the python process by going to the terminal and pressing Ctrl + c, which will output the following log:
INFO: 127.0.0.1:42746 - "POST /test HTTP/1.1" 200 OK ^CINFO: Shutting down INFO: Waiting for connections to close. (CTRL+C to force quit) ^CINFO: Finished server process [16982] ERROR: Traceback (most recent call last): File "/home/vscode/.local/lib/python3.9/site-packages/starlette/routing.py", line 638, in lifespan await receive() File "/home/vscode/.local/lib/python3.9/site-packages/uvicorn/lifespan/on.py", line 137, in receive return await self.receive_queue.get() File "/usr/local/lib/python3.9/asyncio/queues.py", line 166, in get await getter asyncio.exceptions.CancelledError
ERROR: Exception in ASGI application Traceback (most recent call last): File "/home/vscode/.local/lib/python3.9/site-packages/uvicorn/protocols/http/h11_impl.py", line 403, in run_asgi result = await app(self.scope, self.receive, self.send) File "/home/vscode/.local/lib/python3.9/site-packages/uvicorn/middleware/proxy_headers.py", line 78, in call return await self.app(scope, receive, send) File "/home/vscode/.local/lib/python3.9/site-packages/fastapi/applications.py", line 269, in call await super().call(scope, receive, send) File "/home/vscode/.local/lib/python3.9/site-packages/starlette/applications.py", line 124, in call await self.middleware_stack(scope, receive, send) File "/home/vscode/.local/lib/python3.9/site-packages/starlette/middleware/errors.py", line 162, in call await self.app(scope, receive, _send) File "/home/vscode/.local/lib/python3.9/site-packages/starlette/exceptions.py", line 82, in call await self.app(scope, receive, sender) File "/home/vscode/.local/lib/python3.9/site-packages/fastapi/middleware/asyncexitstack.py", line 18, in call await self.app(scope, receive, send) File "/home/vscode/.local/lib/python3.9/site-packages/starlette/routing.py", line 670, in call await route.handle(scope, receive, send) File "/home/vscode/.local/lib/python3.9/site-packages/starlette/routing.py", line 266, in handle await self.app(scope, receive, send) File "/home/vscode/.local/lib/python3.9/site-packages/starlette/routing.py", line 65, in app response = await func(request) File "/home/vscode/.local/lib/python3.9/site-packages/fastapi/routing.py", line 192, in app body = await request.form() File "/home/vscode/.local/lib/python3.9/site-packages/starlette/requests.py", line 254, in form self._form = await multipart_parser.parse() File "/home/vscode/.local/lib/python3.9/site-packages/starlette/formparsers.py", line 190, in parse async for chunk in self.stream: File "/home/vscode/.local/lib/python3.9/site-packages/starlette/requests.py", line 219, in stream message = await self._receive() File "/home/vscode/.local/lib/python3.9/site-packages/uvicorn/protocols/http/h11_impl.py", line 540, in receive await self.message_event.wait() File "/usr/local/lib/python3.9/asyncio/locks.py", line 226, in wait await fut asyncio.exceptions.CancelledError INFO: 127.0.0.1:42752 - "POST /test HTTP/1.1" 500 Internal Server Error