django UnreadablePostError: request data read error

Question

I'm working on django project and I got this error email.

Stack trace

File "/usr/local/lib/python2.7/dist-packages/Django-1.4.3-py2.7.egg/django/core/handlers/wsgi.py", line 180, in _get_post
    self._load_post_and_files()

File "/usr/local/lib/python2.7/dist-packages/Django-1.4.3-py2.7.egg/django/http/__init__.py", line 379, in _load_post_and_files
    self._post, self._files = QueryDict(self.body, encoding=self._encoding), MultiValueDict()

File "/usr/local/lib/python2.7/dist-packages/Django-1.4.3-py2.7.egg/django/http/__init__.py", line 335, in body
    self._body = self.read()

File "/usr/local/lib/python2.7/dist-packages/Django-1.4.3-py2.7.egg/django/http/__init__.py", line 391, in read
    return self._stream.read(*args, **kwargs)

File "/usr/local/lib/python2.7/dist-packages/Django-1.4.3-py2.7.egg/django/core/handlers/wsgi.py", line 98, in read
    result = self.buffer + self._read_limited()

File "/usr/local/lib/python2.7/dist-packages/Django-1.4.3-py2.7.egg/django/core/handlers/wsgi.py", line 92, in _read_limited
    result = self.stream.read(size)

UnreadablePostError: request data read error

Why this error is happening ?
How to solve?

Answer 1

Why this error is happening ?

because the server is recieving a malformed request, which can happen for many reasons. someone might've canceled loading the page, someone might have a crappy internet connection that cut out, cosmic rays could have flipped a bit.

it's not something you really need to worry about until it starts happening very frequently. you might want to make a note when these errors happen and see if it's consequently on the same page or not.

How to solve?

you can't. not at this point at least. gather some more data on when this bug occurs exactly. see if you can find a way to trigger it manually.

Answer 2

With an application at scale, you'll always get the occasional cancelled request. If you're receiving 500 emails they can be quite tedious.

I wouldn't advise completely ignoring them. If UnreadablePostErrors are pouring in, then something's wrong e.g. longer response times causes users to cancel requests.

My solution was a custom filter for admin emails where you can put any logic you want.

The simplest is probably to randomly ignore 19 out of 20 UnreadablePostErrors. That way, if something goes wrong i'll still be informed, but i'll be pestered 20x less.

If you want something more fancy, I'd go @pztrick's solution.

import logging
import random
from django.http import UnreadablePostError

class ReduceUnreadablePostErrors(logging.Filter):
    def filter(self, record):
        if record.exc_info:
            exc_value = record.exc_info[1]
            if isinstance(exc_value, UnreadablePostError):
                return random.randint(1,20) % 20==0
        return True

settings.py:

'filters': {
   'reduce_unreadable_post_errors' : {
        '()' : 'path.to.your.ReduceUnreadablePostErrors'
    },

    ...

'handlers': {
    'mail_admins': {
        'level': 'ERROR',
        'filters': ['require_debug_false','reduce_unreadable_post_errors'],
        'class': 'common.utils.log.AdminEmailHandlerWithEmail'
     },

     ...