Empty /error log lines (a lot of them)

[Maxim Dounin]

Hello!

On Tue, Jan 03, 2012 at 03:32:36PM +0200, Cabbar Duzayak wrote:

> Hi,
> 
> I am using NGINX 0.8.54 on Ubuntu 11.04, and I am getting a lot of
> weird log entries in nginx access file. The structure is somewhat like
> below, but as  you can see there is no method, URL, referer, user
> agent, etc. And, I see bunch of entries for different IP addresses (3
> to 30-40 entries per IP)
> 
> It might be a browser issue, but since I am seeing a lot of these, I
> just wanted to ask here if anyone has seen this before.
> 
> Thanks...
> 
> 
> <USER_IP_ADDRESS> - - [07/Oct/2011:17:11:22 +0300] "-" 400 0 "-" "-"

[...]

Such lines appear when client opens a connection and doesn't send 
valid request (e.g. just closes the connection).

Some modern browsers (e.g. Chrome) tend to open several extra 
connections "just in case" and close them once they realize they 
have no requests to send (and thus they cause such lines to 
appear).

Another common reason is health checks from external balancers, 
but it's probably not your case.

Maxim Dounin