Dropped connections on our Nginx

[Maxim Dounin]

Hello!

On Wed, Jun 20, 2012 at 10:52:36AM +0800, Mauro Stettler wrote:

[...]

> When the problem happens, i see statements like this one in the access
> log. As you can see the Nginx says HTTP status code and length both
> are 0:
> <ip> - - [20/Jun/2012:04:13:23 +0200] "POST
> /userProfile/rateResult?userId=<id>&_csrf_token=7e23ef60c67800c4765d32b0536fc536&rate=5
> HTTP/1.1" 0 0 "<referer>" "Mozilla/5.0 (X11; U; Linux x86_64; en-US;
> rv:1.9.1.6) Gecko/20091216 Mandriva Linux/1.9.1.6-0.1mdv2010.0
> (2010.0) Firefox/3.5.6"

The status 0 suggests there is a major problem which caused 
request to be terminated abnormally before status was set.  This 
might happen if there is lack of some resources (e.g. no memory) - 
this should have an entry in error log though.

Alternatively, this might happen due to some bug, which doesn't 
seems unrealistic specially given the number of 3rd party modules 
you use.

[...]

> Now I don't really know what else to check anymore... I would be
> really glad if somebody had some ideas?

I would recommend to:

1. Try to reproduce the problem without 3rd party modules/patches.

2. Try to obtain debug log of a problematic request.

See here for more details:
http://wiki.nginx.org/Debugging

Maxim Dounin