502 in Nginx as a reverse proxy whithout cache

[marc.cortinas]

Hi,

 Currently, we use Nginx as a reverse proxy without cache. Last monday we've
rolled out a new version of PHP application which has appeared a several 502
errors.

 First of all, i've applied the workaround explained in thread
http://forum.nginx.org/read.php?2,188352 . The number of 502 have falled
down but we can see a several 502 yet, but we haven't any error log now in
the nginx.

 This is Nginx parameters applied:
{code}
 ## Size Limits
  client_body_buffer_size     128K;
  client_header_buffer_size   1M;
  client_max_body_size          1M;
  large_client_header_buffers 8 8k;

 ## Timeouts
  client_body_timeout   600;
  client_header_timeout 600;
  expires               24h;
  keepalive_timeout     60 60;
  send_timeout          600;

 ## TCP options
  tcp_nodelay on;
  tcp_nopush  on;

  ## Proxy caching options
  proxy_buffering           on;
  proxy_buffers 16 16k;
  proxy_buffer_size 32k;

  fastcgi_buffers 16 16k;
  fastcgi_buffer_size 32k;

proxy_next_upstream error timeout http_500 http_502 http_503 http_504;
proxy_connect_timeout 60s;
proxy_read_timeout 600s;
proxy_send_timeout 600s;
{code}


 This is the trace lines in acces log of Nginx and Apache:

Las trazas son estas:
NGINX
log_format  main  '$remote_addr - $remote_user [$time_local] "$request" '
                      '$status $body_bytes_sent "$http_referer" '
                      '"$http_user_agent" "$http_x_forwarded_for"';
{code}
2.139.8.108 - - [31/Jul/2013:23:19:31 +0200] "GET
/es/descuentos-malaga/oferta-pelsandbody-masaje-tailandes-aromaterapia.html?mktc=AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA&utm_campaign=AAAAA&utm_content=AAAAAAA&utm_medium=email&utm_source=ExactTarget&email=emailbos at provider.com&date=AAAAAAA&AL_Hash=AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA&utm_referrer=
HTTP/1.1" 502 118
"http://es.example.com/descuentos-malaga/oferta-pelsandbody-masaje-tailandes-aromaterapia.html?mktc=AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA&utm_campaign=AAAAA&utm_content=AAAAAAA&utm_medium=email&utm_source=ExactTarget&email=emailbos@provider.com&date=AAAAAAA&AL_Hash=AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA"
"Mozilla/5.0 (Linux; U; Android 2.3.3; es-es; GT-I9100 Build/GINGERBREAD)
AppleWebKit/533.1 (KHTML, like Gecko) Version/4.0 Mobile Safari/533.1" "-"
{code}

LogFormat "\"%{True-Client-IP}i\" %h %t %T \"%r\" %>s %b
%{outstream}n/%{instream}n (%{ratio}n%%) \"%{Referer}i\" \"%{Expires}o\"
\"%{Cache-Control}o\" \"%{User-Agent}i\" \"%{Host}i\"
\"%{X-Forwarded-For}i\" %{mod_php_memory_usage}n %P" itsysprod

APACHE
{code}
"-" 10.253.1.61 [31/Jul/2013:23:19:31 +0200] 0 "GET
/es/descuentos-malaga/oferta-pelsandbody-masaje-tailandes-aromaterapia.html?mktc=AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA&utm_campaign=AAAAA&utm_content=AAAAAAA&utm_medium=email&utm_source=ExactTarget&email=emailbos at provider.com&date=AAAAAAA&AL_Hash=AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA
HTTP/1.0" 200 303 285/475 (60%)
"http://es.example.com/descuentos-malaga/oferta-pelsandbody-masaje-tailandes-aromaterapia.html?mktc=AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA&utm_campaign=AAAAA&utm_content=AAAAAAA&utm_medium=email&utm_source=ExactTarget&email=emailbos@provider.com&date=AAAAAAA&AL_Hash=AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA"
"Thu, 19 Nov 1981 08:52:00 GMT" "no-store, no-cache, must-revalidate,
post-check=0, pre-check=0" "Mozilla/5.0 (Linux; U; Android 2.3.3; es-es;
GT-I9100 Build/GINGERBREAD) AppleWebKit/533.1 (KHTML, like Gecko)
Version/4.0 Mobile Safari/533.1" "m.example.com" "2.139.8.108, 10.253.1.60"
786432 30962
{code}

Platform description
# cat /etc/redhat-release 
CentOS release 6.3 (Final)
# uname -a
Linux balance01-prod 2.6.32-279.5.2.el6.x86_64 #1 SMP Fri Aug 24 01:07:11
UTC 2012 x86_64 x86_64 x86_64 GNU/Linux
# nginx -v
nginx version: nginx/1.2.4

Posted at Nginx Forum: http://forum.nginx.org/read.php?2,241447,241447#msg-241447