here is some information I got from the error.log
[10-Apr-2018 12:36:06] WARNING: [pool www] seems busy (you may need to increase pm.start_servers, or pm.min/max_spare_servers), spawning 8 children, there are 2 idle, and 11 total children
[10-Apr-2018 12:36:07] WARNING: [pool www] seems busy (you may need to increase pm.start_servers, or pm.min/max_spare_servers), spawning 16 children, there are 3 idle, and 14 total children
[10-Apr-2018 12:36:08] WARNING: [pool www] seems busy (you may need to increase pm.start_servers, or pm.min/max_spare_servers), spawning 32 children, there are 4 idle, and 16 total children
[10-Apr-2018 12:36:09] WARNING: [pool www] seems busy (you may need to increase pm.start_servers, or pm.min/max_spare_servers), spawning 32 children, there are 4 idle, and 17 total children
[11-Apr-2018 13:21:32] NOTICE: Terminating …
[11-Apr-2018 13:21:32] NOTICE: exiting, bye-bye!
[11-Apr-2018 13:23:53] NOTICE: fpm is running, pid 3560
[11-Apr-2018 13:23:53] NOTICE: ready to handle connections
[11-Apr-2018 13:23:53] NOTICE: systemd monitor interval set to 10000ms
[11-Apr-2018 13:32:55] NOTICE: Terminating …
[11-Apr-2018 13:32:55] NOTICE: exiting, bye-bye!
[11-Apr-2018 13:33:36] NOTICE: fpm is running, pid 969
[11-Apr-2018 13:33:36] NOTICE: ready to handle connections
[11-Apr-2018 13:33:36] NOTICE: systemd monitor interval set to 10000ms