Spent about 5 hours trying to figure out why php-fpm 7.2 was sending a timeout to nginx inside a CentOS 7 container. In the end I couldn't figure it out, downgraded to PHP 7.1 and then everything start working fine. I really hate using CentOS for containers since it also requires privileged mode to be able to start services. Hopefully I can move away from using CentOS for containers soon since the base image is also quite fat.