"Zero size buf" Error on file upload

[Maxim Dounin]

Hello!

On Sat, Feb 01, 2014 at 12:01:17AM -0500, DamienR wrote:

> Hi,
> 
> I have a nginx server doing ffmpeg video conversions, we've noticed if we
> upload a file around 100Mb in size it won't upload and throws a "zero buf"
> error in nginx log; other logs not capture anything.
> 
> 2014/01/31 22:18:49 [alert] 27455#0: *90757882 zero size buf in output t:0
> r:0 f:1 0000000000000000 0000000000000000-0000000000000000 00000000023B4E68
> 0-0 while sending request to upstream, client: 120.xxx.x.51, server:
> www.video.domain.com, request: "POST /ajax/language HTTP/1.1", upstream:
> "fastcgi://127.0.0.1:9000", host: "video.domain.com", referrer:
> "http://video.domain.com/upload/video"
> 
> This is also from wordpress install on the same server
> 
> 2014/01/31 22:23:26 [alert] 27448#0: *90768658 zero size buf in output t:0
> r:0 f:1 0000000000000000 0000000000000000-0000000000000000 00000000024DB4D8
> 0-0 while sending request to upstream, client: xxx.61.14.155, server:
> domain.com.au, request: "POST
> /wp-cron.php?doing_wp_cron=1391225006.5313498973846435546875 HTTP/1.0",
> upstream: "fastcgi://127.0.0.1:9000", host: "domain.com.au"
> 
> build:
> 
> nginx version: nginx/1.4.4
> built by gcc 4.4.7 20120313 (Red Hat 4.4.7-4) (GCC)
> TLS SNI support enabled
> configure arguments: --sbin-path=/usr/local/sbin --with-http_mp4_module
> --with-http_flv_module --with-http_gzip_static_module --with-http_gzip_stati
> c_module --with-http_ssl_module --with-http_spdy_module
> --with-http_secure_link_module --with-http_ssl_module

Please try the following:

1. Test if you see the problem in 1.5.9.  There is at least one 
bug was fixed which may lead to "zero size buf in output" alerts.  
While it shouldn't affect any real file uploads (it only happened 
on a requests with zero-sized body in some cases), testing with 
latest version is a good idea anyway.

2. If spdy is actually used, try without it.

If it doesn't help, please provide full configuration and a debug 
log of a failed request, see http://wiki.nginx.org/Debugging.

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