[kijin]

PHP-FPM has a ton of debugging, logging, and performance-tuning options, but in most popular distros most of them are disabled by default. If you get a Dockerfile from somewhere and just tweak pm.max_children, you're likely to end up with all the helpful stuff commented out.

[xorcist]

Not reading the manual for software your production environment is built on? Surely you are joking.