PHP-FPM What's the reason fpmstop to be very slow?

nope it won't

Code (Text):

time fpmstop
Redirecting to /bin/systemctl stop php-fpm.service

real    0m0.317s
user    0m0.040s
sys     0m0.068s

 

you can try it yourself and see if it helps.

probably best to let php-fpm auto determine it

It can be problematic as php-fpm child processes may not have enough time to complete their work before being shutdown. Thus resulting in PHP-FPM 502 gateway timeout errors etc. So if set that low you would either need to ensure all php-fpm processes have completed their work before issuing a restart or use reload instead restart

reload service command completes immediately but tells php processes to wait it seems until process_control_timeout if you time the fpmreload command and inspect php-fpm master/child process ids at 9 seconds after fpmreload and 11 seconds after fpmreload you see on 11th second the process ids for php-fpm process change (so after 10s).

Code (Text):

time fpmreload; ps xao pid,ppid,command | grep 'php-fpm[:]'; sleep 9; ps xao pid,ppid,command | grep 'php-fpm[:]'; sleep 2; ps xao pid,ppid,command | grep 'php-fpm[:]';
Reload service php-fpm  done

real    0m0.013s
user    0m0.007s
sys     0m0.006s
19650     1 php-fpm: master process (/usr/local/etc/php-fpm.conf)
19651 19650 php-fpm: pool www
19652 19650 php-fpm: pool www
19653 19650 php-fpm: pool www
19654 19650 php-fpm: pool www
19655 19650 php-fpm: pool www
19656 19650 php-fpm: pool www
19657 19650 php-fpm: pool www
19658 19650 php-fpm: pool www
19650     1 php-fpm: master process (/usr/local/etc/php-fpm.conf)
19651 19650 php-fpm: pool www
19652 19650 php-fpm: pool www
19653 19650 php-fpm: pool www
19654 19650 php-fpm: pool www
19655 19650 php-fpm: pool www
19656 19650 php-fpm: pool www
19657 19650 php-fpm: pool www
19658 19650 php-fpm: pool www
19687     1 php-fpm: master process (/usr/local/etc/php-fpm.conf)
19688 19687 php-fpm: pool www
19689 19687 php-fpm: pool www
19690 19687 php-fpm: pool www
19691 19687 php-fpm: pool www
19692 19687 php-fpm: pool www
19693 19687 php-fpm: pool www
19694 19687 php-fpm: pool www
19695 19687 php-fpm: pool www

versus fpmrestart only completes the actual command after that 10s when using static or dynamic process manager instead of default ondemand where php-fpm process ids change immediately after end of fpmrestart (which still waits that 10s)

Code (Text):

ps xao pid,ppid,command | grep 'php-fpm[:]'; time fpmrestart; ps xao pid,ppid,command | grep 'php-fpm[:]'; sleep 9; ps xao pid,ppid,command | grep 'php-fpm[:]'; sleep 2; ps xao pid,ppid,command | grep 'php-fpm[:]';
19687     1 php-fpm: master process (/usr/local/etc/php-fpm.conf)
19688 19687 php-fpm: pool www
19689 19687 php-fpm: pool www
19690 19687 php-fpm: pool www
19691 19687 php-fpm: pool www
19692 19687 php-fpm: pool www
19693 19687 php-fpm: pool www
19694 19687 php-fpm: pool www
19695 19687 php-fpm: pool www
Gracefully shutting down php-fpm .......... done
Starting php-fpm  done

real    0m10.348s
user    0m0.102s
sys     0m0.059s
19929     1 php-fpm: master process (/usr/local/etc/php-fpm.conf)
19930 19929 php-fpm: pool www
19931 19929 php-fpm: pool www
19932 19929 php-fpm: pool www
19933 19929 php-fpm: pool www
19934 19929 php-fpm: pool www
19935 19929 php-fpm: pool www
19936 19929 php-fpm: pool www
19937 19929 php-fpm: pool www
19929     1 php-fpm: master process (/usr/local/etc/php-fpm.conf)
19930 19929 php-fpm: pool www
19931 19929 php-fpm: pool www
19932 19929 php-fpm: pool www
19933 19929 php-fpm: pool www
19934 19929 php-fpm: pool www
19935 19929 php-fpm: pool www
19936 19929 php-fpm: pool www
19937 19929 php-fpm: pool www
19929     1 php-fpm: master process (/usr/local/etc/php-fpm.conf)
19930 19929 php-fpm: pool www
19931 19929 php-fpm: pool www
19932 19929 php-fpm: pool www
19933 19929 php-fpm: pool www
19934 19929 php-fpm: pool www
19935 19929 php-fpm: pool www
19936 19929 php-fpm: pool www
19937 19929 php-fpm: pool www

compare that to centos 7 systemd based php-fpm workaround mentioned, the php-fpm processes change immediately on completion of fpmrestart command which only takes 0.344s

Code (Text):

ps xao pid,ppid,command | grep 'php-fpm[:]'; time fpmrestart; ps xao pid,ppid,command | grep 'php-fpm[:]'; sleep 9; ps xao pid,ppid,command | grep 'php-fpm[:]'; sleep 2; ps xao pid,ppid,command | grep 'php-fpm[:]';
 5704     1 php-fpm: master process (/usr/local/etc/php-fpm.conf)
 5705  5704 php-fpm: pool www
 5706  5704 php-fpm: pool www
 5707  5704 php-fpm: pool www
 5708  5704 php-fpm: pool www
 5709  5704 php-fpm: pool www
 5710  5704 php-fpm: pool www
 5711  5704 php-fpm: pool www
 5712  5704 php-fpm: pool www
Redirecting to /bin/systemctl restart php-fpm.service

real    0m0.344s
user    0m0.038s
sys     0m0.035s
 5815     1 php-fpm: master process (/usr/local/etc/php-fpm.conf)
 5816  5815 php-fpm: pool www
 5817  5815 php-fpm: pool www
 5818  5815 php-fpm: pool www
 5819  5815 php-fpm: pool www
 5820  5815 php-fpm: pool www
 5821  5815 php-fpm: pool www
 5822  5815 php-fpm: pool www
 5823  5815 php-fpm: pool www
 5815     1 php-fpm: master process (/usr/local/etc/php-fpm.conf)
 5816  5815 php-fpm: pool www
 5817  5815 php-fpm: pool www
 5818  5815 php-fpm: pool www
 5819  5815 php-fpm: pool www
 5820  5815 php-fpm: pool www
 5821  5815 php-fpm: pool www
 5822  5815 php-fpm: pool www
 5823  5815 php-fpm: pool www
 5815     1 php-fpm: master process (/usr/local/etc/php-fpm.conf)
 5816  5815 php-fpm: pool www
 5817  5815 php-fpm: pool www
 5818  5815 php-fpm: pool www
 5819  5815 php-fpm: pool www
 5820  5815 php-fpm: pool www
 5821  5815 php-fpm: pool www
 5822  5815 php-fpm: pool www
 5823  5815 php-fpm: pool www

but restart kills PHP processes immediately so get 502 if you still have php-fpm worker processes doing work - for graceful restart always use reload

with CentOS 7 systemd PHP-FPM reload which waits that 10s

Code (Text):

time fpmreload; ps xao pid,ppid,command | grep 'php-fpm[:]'; sleep 2; ps xao pid,ppid,command | grep 'php-fpm[:]'; sleep 9; ps xao pid,ppid,command | grep 'php-fpm[:]'; 
Redirecting to /bin/systemctl reload php-fpm.service

real    0m0.182s
user    0m0.033s
sys     0m0.040s
20150     1 php-fpm: master process (/usr/local/etc/php-fpm.conf)
20151 20150 php-fpm: pool www
20152 20150 php-fpm: pool www
20153 20150 php-fpm: pool www
20154 20150 php-fpm: pool www
20155 20150 php-fpm: pool www
20156 20150 php-fpm: pool www
20157 20150 php-fpm: pool www
20158 20150 php-fpm: pool www
20150     1 php-fpm: master process (/usr/local/etc/php-fpm.conf)
20151 20150 php-fpm: pool www
20152 20150 php-fpm: pool www
20153 20150 php-fpm: pool www
20154 20150 php-fpm: pool www
20155 20150 php-fpm: pool www
20156 20150 php-fpm: pool www
20157 20150 php-fpm: pool www
20158 20150 php-fpm: pool www
20231     1 php-fpm: master process (/usr/local/etc/php-fpm.conf)
20232 20231 php-fpm: pool www
20233 20231 php-fpm: pool www
20234 20231 php-fpm: pool www
20235 20231 php-fpm: pool www
20236 20231 php-fpm: pool www
20237 20231 php-fpm: pool www
20238 20231 php-fpm: pool www
20239 20231 php-fpm: pool www

you can always revert to old init.d php-fpm service method if switching systemd doesn't work. I've added to php-systemd.sh script a restore command to revert to init.d php-fpm service method too if systemd php-fpm service doesn't work 100%

switch to systemd php-fpm service

Code (Text):

curl -sL https://gist.githubusercontent.com/centminmod/a84a86775925ea558fece1f0ac130be3/raw/php-systemd.sh | bash

Code (Text):

curl -sL https://gist.githubusercontent.com/centminmod/a84a86775925ea558fece1f0ac130be3/raw/php-systemd.sh | bash
Gracefully shutting down php-fpm ..... done
systemctl daemon-reload

systemctl restart php-fpm

systemctl enable php-fpm

systemctl status php-fpm
● php-fpm.service - PHP FastCGI Process Manager
   Loaded: loaded (/usr/lib/systemd/system/php-fpm.service; enabled; vendor preset: disabled)
  Drop-In: /etc/systemd/system/php-fpm.service.d
           └─limit.conf
   Active: active (running) since Sat 2019-01-26 06:17:50 UTC; 88ms ago
 Main PID: 8360 (php-fpm)
   CGroup: /system.slice/php-fpm.service
           ├─8360 php-fpm: master process (/usr/local/etc/php-fpm.conf)
           ├─8361 php-fpm: pool www
           ├─8362 php-fpm: pool www
           ├─8363 php-fpm: pool www
           ├─8364 php-fpm: pool www
           ├─8365 php-fpm: pool www
           ├─8366 php-fpm: pool www
           ├─8367 php-fpm: pool www
           └─8368 php-fpm: pool www

Jan 26 06:17:50 test.com systemd[1]: Starting PHP FastCGI Process Manager...
Jan 26 06:17:50 test.com systemd[1]: Started PHP FastCGI Process Manager.

restore to init.d php-fpm service method

Code (Text):

curl -sL https://gist.githubusercontent.com/centminmod/a84a86775925ea558fece1f0ac130be3/raw/php-systemd.sh | bash -s restore

Code (Text):

curl -sL https://gist.githubusercontent.com/centminmod/a84a86775925ea558fece1f0ac130be3/raw/php-systemd.sh | bash -s restore
systemctl daemon-reload

service php-fpm start
Starting php-fpm  done

chkconfig on

service php-fpm status
php-fpm (pid 8697) is running...

To discuss php-systemd.sh itself, started a thread at CentOS 7 Proper PHP-FPM systemd service file