How to set nginx max open files? - linux

Question

Though I have done the following setting, and even restarted the server:
# head /etc/security/limits.conf -n2
www-data soft nofile -1
www-data hard nofile -1
# /sbin/sysctl fs.file-max
fs.file-max = 201558
The open files limitation of specific process is still 1024/4096:
# ps aux | grep nginx
root 983 0.0 0.0 85872 1348 ? Ss 15:42 0:00 nginx: master process /usr/sbin/nginx
www-data 984 0.0 0.2 89780 6000 ? S 15:42 0:00 nginx: worker process
www-data 985 0.0 0.2 89780 5472 ? S 15:42 0:00 nginx: worker process
root 1247 0.0 0.0 11744 916 pts/0 S+ 15:47 0:00 grep --color=auto nginx
# cat /proc/984/limits
Limit Soft Limit Hard Limit Units
Max cpu time unlimited unlimited seconds
Max file size unlimited unlimited bytes
Max data size unlimited unlimited bytes
Max stack size 8388608 unlimited bytes
Max core file size 0 unlimited bytes
Max resident set unlimited unlimited bytes
Max processes 15845 15845 processes
Max open files 1024 4096 files
Max locked memory 65536 65536 bytes
Max address space unlimited unlimited bytes
Max file locks unlimited unlimited locks
Max pending signals 15845 15845 signals
Max msgqueue size 819200 819200 bytes
Max nice priority 0 0
Max realtime priority 0 0
Max realtime timeout unlimited unlimited us
I've tried all possible solutions from googling but in vain. What setting did I miss?

Answer 1

On CentOS (tested on 7.x):
Create file /etc/systemd/system/nginx.service.d/override.conf with the following contents:
[Service]
LimitNOFILE=65536
Reload systemd daemon with:
systemctl daemon-reload
Add this to Nginx config file:
worker_rlimit_nofile 16384; (has to be smaller or equal to LimitNOFILE set above)
And finally restart Nginx:
systemctl restart nginx
You can verify that it works with cat /proc/<nginx-pid>/limits.

Answer 2

I found the answer in few minutes after posting this question...
# cat /etc/default/nginx
# Note: You may want to look at the following page before setting the ULIMIT.
# http://wiki.nginx.org/CoreModule#worker_rlimit_nofile
# Set the ulimit variable if you need defaults to change.
# Example: ULIMIT="-n 4096"
ULIMIT="-n 15000"
/etc/security/limit.conf is used by PAM, so it shoud be nothing to do with www-data (it's nologin user).

Answer 3

For nginx simply editing nginx.conf and setting worker_rlimit_nofile should change the limitation.
I initially thought it is a self-imposed limit of nginx, but it increases limit per process:
worker_rlimit_nofile 4096;
You can test by getting a nginx process ID (from top -u nginx), then run:
cat /proc/{PID}/limits
To see the current limits
Another way on CentOS 7 is by systemctl edit SERVICE_NAME, add the variables there:
[Service]
LimitNOFILE=65536
save that file and reload the service.

Answer 4

For those looking for an answer for pre-systemd Debian machines, the nginx init script executes /etc/default/nginx. So, adding the line
ulimit -n 9999
will change the limit for the nginx daemon without messing around with the init script.
Adding ULIMIT="-n 15000" as in a previous answer didn't work with my nginx version.