'socket' object has no attribute 'sendfile' while sending a file in flask guni-CodePudding

Using flask, I'm trying to send a file to the user on clicking a button in UI using send_from_directory function. It used to work fine. I wanted to change the repo and since changing it, I'm no more able to download the file. On looking at the supervisor log, I see this:

[9617] [ERROR] Error handling request
Traceback (most recent call last):
  File "path_to_file/venv/lib/python3.4/site-packages/gunicorn/workers/sync.py", line 182, in handle_request
    resp.write_file(respiter)
  File "path_to_file/venv/lib/python3.4/site-packages/gunicorn/http/wsgi.py", line 385, in write_file
    if not self.sendfile(respiter):
  File "path_to_file/venv/lib/python3.4/site-packages/gunicorn/http/wsgi.py", line 375, in sendfile
    self.sock.sendfile(respiter.filelike, count=nbytes)
AttributeError: 'socket' object has no attribute 'sendfile'

In the same repo, this works fine locally. But when trying in remote server using the gunicorn supervisor nginx setup, I get the above error message. I do get 200 Ok response in the application log file. Spent a lot of time trying to fix but without success.

Also, the notable difference between the working app between the previous repo and the non-working current repo is the python version. Previous: python2.7, Current: python3.4

CodePudding user response：

For me, usually when a script works locally but not when hosted its one (or more) of these possibilities:

Location / path to the files is different
older version of python
older version of the library

CodePudding user response：

Pointing the virtual env to Python 3.6 and upgrading all the relevant libraries including Flask resolved the issue.