Help with debugging - stall on response size is a symptom but what is the cause?

[Maxim Dounin]

Hello!

On Sun, Feb 12, 2012 at 09:21:35PM -0500, LetsPlay wrote:

> > nginx -V
> nginx: nginx version: nginx/1.0.5
> nginx: TLS SNI support enabled
> nginx: configure arguments: --prefix=/etc/nginx
> --conf-path=/etc/nginx/nginx.conf
> --error-log-path=/var/log/nginx/error.log
> --http-client-body-temp-path=/var/lib/nginx/body
> --http-fastcgi-temp-path=/var/lib/nginx/fastcgi
> --http-log-path=/var/log/nginx/access.log
> --http-proxy-temp-path=/var/lib/nginx/proxy
> --http-scgi-temp-path=/var/lib/nginx/scgi
> --http-uwsgi-temp-path=/var/lib/nginx/uwsgi
> --lock-path=/var/lock/nginx.lock --pid-path=/var/run/nginx.pid
> --with-debug --with-http_addition_module --with-http_dav_module
> --with-http_geoip_module --with-http_gzip_static_module
> --with-http_image_filter_module --with-http_realip_module
> --with-http_stub_status_module --with-http_ssl_module
> --with-http_sub_module --with-http_xslt_module --with-ipv6
> --with-sha1=/usr/include/openssl --with-md5=/usr/include/openssl
> --with-mail --with-mail_ssl_module
> --add-module=/build/buildd/nginx-1.0.5/debian/modules/nginx-echo
> --add-module=/build/buildd/nginx-1.0.5/debian/modules/nginx-upstream-fair
> 
> Logs: http://pastebin.com/W4Tf0vcF
> 
> Here is a summary again:
> 
> Details: 
> System: Ubuntu 11.10, Play 1.2.4 unzipped and installed, Nginx 1.0.5 
> via apt-get 
> Network: www.myApp.com points to a static IP, which is a modem/router 
> with LAN address 192.168.1.1 wired to my box 192.168.1.13.  The router 
> uses the NAT rule "forward port 80 to 192.168.1.13" (my box) 
> Note that local access (http://localhost:9027) works fine in all cases 
> Case 1: WORKS vanilla "play new myApp" works fine at
> http://localhost:9027 
> Case 2: FAIL vanilla "play new myApp" times out at http://www.myApp.com,
> 
> nothing received by browser 
> Case 3: WORKS hacked index.html with short toy css, works via
> www.myApp.com 
> Case 4: FAIL Case 3 with lengthened css, long delay via www.myApp.com, 
> css not used 
> Case 5: WORKS Case 4 but with nginx "proxy_buffering off;", works via 
> www.myApp.com 
> Case 6: FAIL Case 5 with an extra css comment line, long delay via 
> www.myApp.com, css not used

Please try connecting nginx directly, not via NAT.  There is 
nothing wrong in logs as far as I see, and described 
problem looks very similar to classic MTU issues.  See here for 
details:

http://en.wikipedia.org/wiki/Maximum_transmission_unit#Path_MTU_Discovery

Maxim Dounin