Nginx uWSGI responses truncated

After double-checking that the uwsgi command I was testing against matched all the options I'd provided in my .ini file, I realized that my .ini file contained processes = 5 while the uwsgi command I was testing with did not. If I add --processes=5 to my uwsgi command, I can reproduce the truncation issue on every hit, not just on every second request. Each time I start the uwsgi server with --processes=5, the first request succeeds, the second yields a 500, and all subsequent requests are truncated to 9.99MB with the following error in the console:

[2017-01-08 04:16:08,959] ERROR in app: Exception on / [GET]
Traceback (most recent call last):
  File "/usr/local/lib/python3.4/dist-packages/flask/app.py", line 1982, in wsgi_app
    response = self.full_dispatch_request()
  File "/usr/local/lib/python3.4/dist-packages/flask/app.py", line 1614, in full_dispatch_request
    rv = self.handle_user_exception(e)
  File "/usr/local/lib/python3.4/dist-packages/flask/app.py", line 1517, in handle_user_exception
    reraise(exc_type, exc_value, tb)
  File "/usr/local/lib/python3.4/dist-packages/flask/_compat.py", line 33, in reraise
    raise value
  File "/usr/local/lib/python3.4/dist-packages/flask/app.py", line 1612, in full_dispatch_request
    rv = self.dispatch_request()
  File "/usr/local/lib/python3.4/dist-packages/flask/app.py", line 1598, in dispatch_request
    return self.view_functions[rule.endpoint](**req.view_args)
  File "./flaskapp.py", line 13, in main
    flag = dont_tread_on_memes.dont_me(caption)
  File "./dont_tread_on_memes/__init__.py", line 30, in dont_me
    return tread_on("don't {} me".format(phrase))
  File "./dont_tread_on_memes/__init__.py", line 16, in tread_on
    flag = BLANK_FLAG.copy()
  File "/usr/local/lib/python3.4/dist-packages/PIL/Image.py", line 1010, in copy
    self.load()
  File "/usr/local/lib/python3.4/dist-packages/PIL/ImageFile.py", line 226, in load
    "(%d bytes not processed)" % len(b))
OSError: image file is truncated (0 bytes not processed)

My suspicion is that this is an issue with Pillow and the way uwsgi handles threading. Perhaps the every-other-request behavior was due to the way uwsgi decides to spawn new processes and kill old processes, or due to caching by NGINX. Either way, I've fixed the truncation issue.

I also found this on StackOverflow from someone with my same issue.

If anyone else can provide an answer for why this occurred, or an answer as to how I can both keep this resolved and can let uwsgi spawn multiple processes, I'd certainly consider that a more complete answer and accept it.

This almost always means that there is a problem with your images (i.e., there is missing data at the bottom). I have processed images > 25mb using PIL (provided you have enough RAM) and it works fine. The workaround here might work for you. Copy & pasted for ease of reading:

if img and img.meta_type == 'Image':
    pilImg = PIL.Image.open( StringIO(str(img.data)) )
elif imgData:
    pilImg = PIL.Image.open( StringIO(imgData) )

try:
    pilImg.load()
except IOError:
    pass # You can always log it to logger