I get a 502 Bad Gateway with nginx when using spawn fcgi to spawn php5-cgi.
I use this to span an instance on server start using the following line in rc.local
/usr/bin/spawn-fcgi -a 127.0.0.1 -p 9000 -u www-data -g www-data -f /usr/bin/php5-cgi -P /var/run/fastcgi-php.pid
presumably I'm getting the error because the spawn-fcgi / php5-cgi dies and there is nothing listening there anymore to parse php.
I get nothing in the logs that I can see anywhere, I'm out of ideas (and new to this setup with nginx)
I executed my localhost
and the page displayed the 502 bad gateway
message. This helped me:
/etc/php5/fpm/pool.d/www.conf
listen = /var/run/php5-fpm.sock
to listen = 127.0.0.1:9000
sudo service php5-fpm restart
Maybe it will help you.
Source from: http://wildlyinaccurate.com/solving-502-bad-gateway-with-nginx-php-fpm