accept() failed (53: Software caused connection abort)

[Maxim Dounin]

Hello!

On Wed, Jul 13, 2011 at 11:07:03AM +0200, Adam PAPAI wrote:

> Dear List,
> 
> We've switched to Nginx because it rocks!
> 
> I have a problem with a really heavy loaded webserver:
> 
> It has 100,000,000 request per day and this number is increasing.
> (Probably 200-300M would be the peak) We are using it with php-fcgi
> backend.
> 
> We have 2 serious constant error messages, can be found below  [1]
> 
> [1] http://pastebin.com/6nQuEqkT
> 
> writev() failed (54: Connection reset by peer)
> accept() failed (53: Software caused connection abort)
> 
> When this error occurs, the 50x page is shown OR totally disconnects
> and "could not connect to server" happens.
> 
> Our system is a:
> 
> FreeBSD iridium 8.2-RELEASE FreeBSD 8.2-RELEASE #0: Thu Feb 17
> 02:41:51 UTC 2011
> root at mason.cse.buffalo.edu:/usr/obj/usr/src/sys/GENERIC  amd64
> 
> HP Proliant G7,
> - 32GB memory
> - CPU: Intel(R) Xeon(R) CPU  @ 2.40GHz x 6 ( x 2 ) = 24 CPU
> - SAS disks
> 
> What do the error messages above mean? Has it problem with the
> nginx, or the PHP, or kernel limits? (TCP limits?)

In no particular order:

2011/07/13 10:20:58 [error] 38061#0: accept() failed (53: Software caused connection abort)

Client closed connection before nginx was able to accept() it.  
This may be normal (i.e. user just closed a browser page while images 
was still loading) and may be not (i.e. nginx wasn't able to 
accept() for a long time due to some problems and client bored 
waiting and closed a page).

Some number of such messages are expected to appear.  High number 
of such errors may indicate problems, try looking at listen queues 
at first (netstat -Lan).

2011/07/13 10:26:56 [error] 38059#0: *73523 writev() failed (54: Connection reset by peer) while sending request to upstream ...

Your upstream reset connection.  This is a problem with your 
backend (most likely it just died).  Inspect backend logs.

2011/07/13 10:31:33 [error] 38060#0: *113640 writev() failed (32: Broken pipe) while sending request to upstream ...

The same as above, but in slightly different moment.

> What should I tuning? What should I set up?

>From here it looks like you have problems with backend(s).

Maxim Dounin