Tweaking FPM config
You may also need to tweak PHP-FPM config to match new sysctl.conf settings.
Open PHP-FPM pool config file:
vim /etc/php5/fpm/pool.d/www.conf
Look for line:
;listen.backlog = 128
Change it to:
listen.backlog = 65536
Restart php5-fpm service.
service php5-fpm restart
Additionally, make sure that operating system limit allows for above value.
Run:
sysctl net.core.somaxconn
Should display value 65536 or higher.
If no, then run following commands to verify.
echo "net.core.somaxconn=65536" >> /etc/sysctl.conf
sysctl -p
Test
Check FPM status page via web interface or command-line:
curl localhost/status
It will display parameters like:
pool: www
process manager: ondemand
start time: 06/Nov/2016:19:02:09 +0800
start since: 2
accepted conn: 4
listen queue: 0
max listen queue: 0
listen queue len: 65536</strong>
idle processes: 1
active processes: 2
total processes: 3
max active processes: 3
max children reached: 0
slow requests: 0
In the output, listen queue len value should match listen.backlog value set in the config.
Using TCP/IP for FPM
Sockets are slightly faster as compared to TCP/IP connection. But they are less scalable by default.
If you start getting errors like below (as faced ovidiu here)
connect() to unix:/var/run/php5-fpm.sock failed or **apr_socket_recv: Connection reset by peer (104)**
Then it means you need to either switch to TCP/IP or tweak with linux-system parameter so that your OS can handle large number of connections.
Open PHP-FPM pool config file
vim /etc/php5/fpm/pool.d/www.conf
Replace line:
listen = /var/run/php5-fpm.sock
by line:
listen = 127.0.0.1:9000
Changes to Nginx
Next, open Nginx virtual-host config file(s).
Look for line
fastcgi_pass unix:/var/run/php5-fpm.sock;
Replace it with
fastcgi_pass 127.0.0.1:9000;
Important: Reload php-fpm and nginx so that changes can take effect.
service php5-fpm reload && service nginx reload
Sysctl.conf Tweaking
Finally, don’t forget to tweak Linux’s sysctl values by following this – https://rtcamp.com/tutorials/linux/sysctl-conf/