Client closed connection: 400 vs 499

[Maxim Dounin]

Hello!

On Mon, Jun 15, 2015 at 11:20:15AM +0300, Sorin Manole wrote:

> Hello,
> 
> It seems that if the client closes the connection during a requests there
> are time when the request is logged as 400 and other times as 499.
> 
> Is there a reason for the difference? Serving of the error page cannot be
> it because the connection is closed anyway.

The "400" code means that no correct request was received - that 
is, client sent a bad request.

The "499" code means that nginx got a request, but wasn't able to 
send a response.  That is, client closed connection before we 
started sending a response.  This, in particular, may happen if a 
backend is slow and nginx isn't able to return a response before 
the client times out.

The difference may be important when looking into logs.

-- 
Maxim Dounin
http://nginx.org/