random 502 gateway errors with nginx php-fpm and ubuntu

Question

I was having an issue with random 502 gateway errors using nginx and php-fpm. In my case I discovered a scenario where various php.ini error_log settings and error_reporting lev

Answer 1

502 gateway errors in Nginx are caused by php-fpm not having enough process and/or timeouts. Logging only tells you what the issues are and are not the cause of 502 errors.

I use stunnel+haproxy+nginx+php-fpm on 25 servers. The defaults in pfp-fpm are very low, even for a moderately busy server. Configure the fpm child processes much the same way you would with apache mod_php.

I use the following:

pm.max_children = 250
pm.start_servers = 20
pm.min_spare_servers =10
pm.max_spare_servers = 20
pm.max_requests = 1500

This is a server with 2GB ram. It serves 20-30GB traffic per day with no 502's