Magento place order / checkout time out - 502 Bad Gateway - php

Question

I'm getting 502 erros when I try to place an order in Magento, I also tried to disable Downloadable products and RSS feeds.
I receive the orde confirmation email, the stock is update and at the admin panel I can see the order correctly but I don't get the success message at checkout/onepage/success/ instead I get an 502 error caused by a timeout.
The only error message that I'm getting is os nginx log:
2013/12/21 18:49:47 [error] 18449#0: *191 recv() failed (104: Connection reset by peer) while reading response header from upstream, client: 177.103.69.141, server: dev.canalagricola.com.br, request: "GET /checkout/onepage/success/ HTTP/1.1", upstream: "fastcgi://127.0.0.1:9000", host: "dev.canalagricola.com.br", referrer: "http://dev.canalagricola.com.br/checkout/onepage/"
I'm using Amazon Linux (64 bits) on a small instance (PHP5.5, PHPFPM-5.5, Nginx 1.4.3, Mysql 5.5, Magento 1.8.1)
magento.conf (nginx)
server {
listen 80;
server_name dev.canalagricola.com.br;
access_log off;
root /var/www/canalagricola;
index index.php;
gzip on;
gzip_min_length 10240;
gzip_comp_level 9;
gzip_proxied expired no-cache no-store private auth;
gzip_types text/plain text/css text/xml text/javascript application/x-javascript application/xml application/xml+rss;
gzip_disable "MSIE [1-6]\.";
sendfile on;
tcp_nodelay on;
tcp_nopush on;
keepalive_timeout 30;
keepalive_requests 100000;
reset_timedout_connection on;
client_body_timeout 10;
send_timeout 2;
location / {
try_files $uri $uri/ #handler;
expires 30d;
}
location ~* \.(jpg|jpeg|gif|png|css|js|ico|xml)$ {
log_not_found off;
expires 1y;
}
location ^~ /(app|includes|lib|media/downloadable|pkginfo|report/config.xml|var)/ { internal; }
location /var/export/ { internal; }
location /. { return 404; }
location #handler { rewrite / /index.php; }
location ~* .php/ { rewrite ^(.*.php)/ $1 last; }
location ~* .php$ {
if (!-e $request_filename) { rewrite / /index.php last; }
expires off;
fastcgi_pass unix:/var/run/php-fpm/php-fpm.sock;
fastcgi_param SCRIPT_FILENAME $document_root$fastcgi_script_name;
fastcgi_param SCRIPT_NAME $fastcgi_script_name;
fastcgi_param MAGE_RUN_CODE default;
fastcgi_param MAGE_RUN_TYPE store;
fastcgi_read_timeout 300;
include fastcgi_params;
}
rewrite ^/minify/([0-9]+)(/.*.(js|css))$ /lib/minify/m.php?f=$2&d=$1 last;
rewrite ^/skin/m/([0-9]+)(/.*.(js|css))$ /lib/minify/m.php?f=$2&d=$1 last;
location /lib/minify/ {
allow all;
}
}
www.conf (php-fpm)
[www]
listen = /var/run/php-fpm/php-fpm.sock
listen.allowed_clients = 127.0.0.1
listen.owner = nginx
listen.group = nginx
listen.mode = 0664
user = nginx
group = nginx
pm = dynamic
pm.max_children = 4
pm.start_servers = 2
pm.min_spare_servers = 1
pm.max_spare_servers = 3
pm.max_requests = 200
request_terminate_timeout = 300s
rlimit_files = 131072
rlimit_core = unlimited
catch_workers_output = yes
php_admin_value[memory_limit] = 1024M
php_admin_value[max_execution_time] = 300000
php_admin_value[error_log] = /var/log/php-fpm/5.5/www-error.log
php_admin_flag[log_errors] = on
php_value[session.save_handler] = files
php_value[session.save_path] = /var/lib/php/5.5/session

Answer 1

apc needs to be disabled few hours, then you can plug it in. and read logs again.
there is eaccelerator as well, works sometimes even better.
disable full page cache and apc and run
ab -c 1 -n 1 http://www.campsaver.com/
then restart with apc
see speed, read logs and enable full page cache if good.

Answer 2

Okay,
The above nginx error indicate that issue is related to the fastcgi(php-fpm).
After enabling the "catch_workers_output" on /etc/php5/fpm/pool.d/www.conf Got the relevant error on php5-fpm.log. Now understand that issue is related to AMQP module.
[21-Aug-2013 23:32:57] WARNING: [pool www] child 16091 said into stderr: "php-fpm: pool www: symbol lookup error: /usr/lib/php5/20090626/amqp.so: undefined symbol: amqp_open_socket"
Issue has been fixed afterrecompiled and install amqp module

Answer 3

I notice you are using PHP 5.5
According to the requirements the recommended PHP version to use is 5.2.13 - 5.3.24
http://magento.com/resources/system-requirements
Install the recommended PHP version to see if you have any issue.

Answer 4

Restart your PHP-FPM:
/etc/init.d/php55-php-fpm restart
If this issue persists, you can increase buffer and timeouts inside HTTP block:
http {
...
fastcgi_buffers 8 16k;
fastcgi_buffer_size 32k;
fastcgi_connect_timeout 300;
fastcgi_send_timeout 300;
fastcgi_read_timeout 300;
...
}