Is there any update on this issue? I have the same problem, just migrated fromv0.103.0tov0.108.0and realized my tests are failing due the same issue. Is is related tothis breaking change?
If yes, what is the proposed approach for handling the UploadFile in the background task?
my old practice is written below

asyncdefupload_csv_to_gcloud_blob_storage(
self,file:UploadFile,bucket_name:str,blob_storage_path:str
):
"""write the data to a bucket with" ""
storage_client=storage.Client()
csv_bucket=storage_client.bucket(bucket_name)
blob=csv_bucket.blob(blob_storage_path)

try:
withblob.open("wb")asbuffer:
shutil.copyfileobj(file.file,buffer)
finally:
file.file.close()

@app.post("/csv_tables")
asyncdefupload_csv(
csv_file:Annotated[UploadFile,File()],
background_tasks:BackgroundTasks,
):

background_tasks.add_task(
upload_csv_to_gcloud_blob_storage,
csv_file=csv_file,
bucket_name="csv",
blob_storage_path="csv_path",
)
return"OK"

We ran into this issue. Callingfile.read()in code our began raising an error after upgrading fastapi:ValueError: I/O operation on closed file.

I'm having similar issue with a tempfile I'm yielding....

def create_temp_file():
fd, path = tempfile.mkstemp(suffix='.csv')
try:
yield fd, path
finally:
os.unlink(path)

When I try to return the file in a FileResponse I hit:
RuntimeError(f "File at path {self.path} does not exist." )

Is there any update on this issue? I have the same problem, just migrated fromv0.103.0tov0.108.0and realized my tests are failing due the same issue. Is is related tothis breaking change?If yes, what is the proposed approach for handling the UploadFile in the background task? my old practice is written below

It seems to be, removing this line prevent the file in the body from being closed:https://github /tiangolo/fastapi/blob/958425a899642d1853a1181a3b89dcb07aabea4f/fastapi/routing.py#L231

It was introduced in the only commit changing the code between versions 105 and 106:
a4aa79e#diff-4d573079004a9f3d148baa4658e68e82b8a3d1a95d603fee8177daa92cf65c93R231

Unfortunately theget_request_handleris not trivial, so I cannot create PR without a bit of help.

I went through theget_request_handlerfunction again and maybe the behavior is intentional? I don't know. Anyway the problem is that it simply runs the endpoint handler:
https://github /tiangolo/fastapi/blob/958425a899642d1853a1181a3b89dcb07aabea4f/fastapi/routing.py#L294
and then closes the file. But in case the handler is asynchronous, like a background task:

@app.post(...)
asyncdeffoo():
background_tasks.add_task(process_recording_file,file=file,...)

it closes the file before the task can actually run. So I created a deep copy like this:

-background_tasks.add_task(process_recording_file, file=file,...)
+background_tasks.add_task(process_recording_file, file=copy.deepcopy(file),...)

and I close the file myself in the function:

asyncdefprocess_recording_file(file:UploadFile...):
try:
...
finally:
awaitfile.close()

which fixes the issue even with the newest version of FastAPI. It is probably not very efficient given that the file is few MB in my case.

So maybe a better question would be, what is the expected usage of UploadFile combined with BackgroundTasks?https://fastapi.tiangolo /tutorial/background-tasks/

Hi,@msehnout

Interesting thinking, but I don't think it's a backstage task. Look at this.:encode/starlette#2176 (comment)

How is my comment related?

I just want to express that the idea of @ msehnout may be backward incompatible because he mentioned background tasks, it seems to have nothing to do with your comments?

I'm having similar issue with a tempfile I'm yielding....

def create_temp_file():
fd, path = tempfile.mkstemp(suffix='.csv')
try:
yield fd, path
finally:
os.unlink(path)

When I try to return the file in a FileResponse I hit:RuntimeError(f "File at path {self.path} does not exist." )

Related discussion:#10850

I am assumingcreate_temp_fileis used as a dependency. This error is happening because the dependency is fully resolved before the response is returned to the client. Previously, this worked because the exit code was executed after the response was sent. At the moment, I think the only way to work around this is using Background Tasks, as discussed in#2512.

I'm not sure the problem I'm experiencing is actually an issue or a bad design choice on my side, so I created a discussion instead:#10936

Any updates on this? deepcopying isn't an option for me.

Looking forward to an update. copy.deepcopy not work for me. I have no choice but to downgrade fastapi

I'm also hitting this. Need to perform some long running processing steps on uploaded files and it's no longer possible with BackgroundTasks due to the file being closed when returning the response. So this promise from theFastAPI docs on BackgroundTasksis now broken.

For example, let's say you receive a file that must go through a slow process, you can return a response of "Accepted" (HTTP 202) and process it in the background.

In case it helps others, for now I'm working around this issue by adding my ownUploadFileclass which wraps and patches thefastapi.UploadFileclass. Tested and it's working as expected.BackgroundTasknow processes data (i.e. uploads to S3) correctly in the background. Don't forget, using this approach you need to close theUploadFilemanually in yourBackgroundTaskor otherwise. Not ideal or a long-term solution but it's doing the job.

fromfastapiimportUploadFileas_UploadFile

classUploadFile(_UploadFile):
"""Patches `fastapi.UploadFile` due to buffer close issue.

See the related github issue:
https://github /tiangolo/fastapi/issues/10857
"""

def__init__(self,upload_file:_UploadFile)->None:
"""Wraps and mutates input `fastapi.UploadFile`.

Swaps `close` method on the input instance so it's a no-op when called
by the framework. Adds `close` method of input as `_close` here, to be
called later with overridden `close` method.
"""
self.filename=upload_file.filename
self.file=upload_file.file
self.size=upload_file.size
self.headers=upload_file.headers

_close=upload_file.close
setattr(upload_file,"close",self._close)
setattr(self,"_close",_close)

asyncdef_close(self)->None:
pass

asyncdefclose(self)->None:# noqa: D102
awaitself._close()

Also running into this, any plans for a timely fix?

We're also hitting this and are stuck with FastAPI 0.105.0 on multiple projects until this is fixed.

Just encoutered similar issue.
I can confirm downgrade to v0.105.0 works for me.

Can anyone upgrade status to this issue to make it more visible/urgent?
It's like very annoying issue and heavy breaking change from v105 to v106.
Simple saving files thats works in 105 stop working in 106. Can't find examples how it should work with background tasks, or guides to migrate to new version.
@Kludex,@tiangolocan you please some help with examples how made simple saving files?

Does anyone have a fix for the background task stuff?

@vicef5the solution I suggested abovehas been working fine for us as a patch until a more long term solution is introduced.

@vicef5the solution I suggested abovehas been working fine for us as a patch until a more long term solution is introduced.

Thanks man
I just downgraded to v105 to get it working

I have the same problem while using background tasks to upload a file (class UploadFile) to a bucket. My temporary solution was to use deepcopy

Hey guys did anyone have a good work around for this? Or is downgrading still the best option

Hey guys did anyone have a good work around for this? Or is downgrading still the best option

Eamonn, downgrading is the easiest solution

+1

+1 😭😭