Why is mod_wsgi not able to write data? IOError: failed to write data

Question

What could be causing this error:

$ sudo tail -n 100 /var/log/apache2/error.log'

[Wed Dec 29 15:20:03 2010] [error] [client 220.181.108.181] mod_wsgi (pid=20343): Exception occurred processing WSGI script '/home/username/public_html/idm.wsgi'.  
[Wed Dec 29 15:20:03 2010] [error] [client 220.181.108.181] IOError: failed to write data

Here is the WSGI script:

$ cat public_html/idm.wsgi 
import os
import sys

sys.path.append('/home/username/public_html/IDM_app/')

os.environ['DJANGO_SETTINGS_MODULE'] = 'settings'

import django.core.handlers.wsgi

application = django.core.handlers.wsgi.WSGIHandler()

Why would Django not be able to write data?

I'm running Django 1.2.4

Related:stackoverflow.com/a/7089413/633961

guettli
– guettli

2013-10-17 12:56:40 +00:00
Commented Oct 17, 2013 at 12:56 — guettli
– guettli, Commented Oct 17, 2013 at 12:56

Graham Dumpleton · Accepted Answer · 2010-12-30 10:46:42Z

31

That error, without any sort of Python traceback, may be a variation on issue described in:

http://code.google.com/p/modwsgi/issues/detail?id=29&can=1

That is, occurs when HTTP client connection is lost before the full response could be written back by the web server. It can manifest as 'client closed connection', 'failed to write data' or 'failed to flush data' IOError in Apache error log only. Ie., not seen by WSGI applicaton because the writing of data is occurring after WSGI application has returned and so can't throw exception back to the application to do anything with.

The question is whether you get an error message from Django if you configure errors to be sent to you in email. If you do, then instead is something happening in Django.

edited Dec 30, 2010 at 10:46

answered Dec 30, 2010 at 7:55

Graham Dumpleton

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3 Comments

gabn88 Over a year ago

But how to solve it? In my application it seems to be related to send_mail (which takes a long time)...

Graham Dumpleton Over a year ago

There is no point adding a vague question with no specific information about your case to an existing followup to someone else's question. Your situation could be completely different. Create a new question explaining in detail your problem.

gabn88 Over a year ago

I'm sorry, but I got the same error, and I configured Django to send email, but got no mail. In my case the problem was that I changed my smtp mailbox password without changing it in Django. Might help someone in the future who is searching for the same problem like I did... No means to do anybody harm!

ubik · Accepted Answer · 2011-05-21 18:00:13Z

6

I have the same problem in an application that uses a lot of AJAX calls (mod_wsgi 3.3). Is there any known solution for this? I thought about just ignoring the exception, but that is normally not a very good idea.

UPDATE

Actually, this can be due to several things, but the most probable cause is that you are using the write callback instead of yielding your output.

I believe this will help:

http://groups.google.com/group/modwsgi/browse_thread/thread/c9cc1307bc10cfff

edited May 21, 2011 at 18:00

answered Mar 29, 2011 at 13:15

ubik

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1 Comment

Graham Dumpleton Over a year ago

Will happen with either write or yield, makes no difference. Django doesn't use write only yield. If write were being used, the error would propagate back into the WSGI application and the application would likely catch it and be converted to a 500 with it not being logged. For the yield, it is mod_wsgi writing the data and no way to propagate error back to application, so mod_wsgi logs error with no traceback as not in context of application.

Community · Accepted Answer · 2017-05-23 12:10:08Z

0

I've found the same problem with my python web app in Digital ocean and after checking the log file seriously I've discovered that It was a problem with my Database mysql ! The problem was due to the fact that I was running out storage (RAM) So check those question and solve the problem!

`For Mysql

And this

Hope It will help

edited May 23, 2017 at 12:10

CommunityBot

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answered May 14, 2017 at 21:37

Espoir Murhabazi

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Comments

chriscauley · Accepted Answer · 2010-12-29 23:26:50Z

-5

I'm wagering it is a permissions issue. True making the target directory/file universally writable. Then make the file owned by your www-data group (or whatever your apache user is), make it group writable, and make sure nothing in that folder is sensitive because this could be a security problem.

answered Dec 29, 2010 at 23:26

chriscauley

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