Returning Large Files With FastAPI and StreamingResponse runs out of memory because read() loads whole file into memory

Question

I've been working with FastAPI and I've noticed that distributing large files is an issue. While I can upload them to a FastAPI server:

    async with aiofiles.open(temp_file_path, 'wb') as f:
        while chunk := await file.read(CHUNK_SIZE):
            await f.write(chunk)

I cannot manage to distribute the files.

For distributing:

file = open(filename, "rb", buffering=10485760)
headers = {'Content-Disposition': 'attachment; filename="' + filename}
return StreamingResponse(content=io.BytesIO(file.read()), media_type="application/octet-stream", headers=headers)
# For context, StreamingResponse is from starlette.responses.StreamingResponse

I tried using the buffering argument, however it looks like this argument just doesn't manage to work.

How can I return a file procedurally so that all of it isn't loaded into memory at once?

Answer 1

Most definitely not my best and brightest moment!!!! FileResponse takes a path parameter, which downloads millions of times faster. If I download the file, then specifying a path and simply letting FastHTTP serve the file works.