How do you properly watch and reload Nginx conf?

Question

I have two questions:

Is there a difference between: nginx -s reload and pkill -HUP -F nginx.pid
What's the simplest way to watch the Nginx conf file and upon changes test the conf file (nginx -t), and if it passes reload Nginx. Can that be done with runit or a process manager like Supervisor?

Is it `-F` or `-f` (I don't have `-F` on my `pkill`) – Déjà vu May 29 '13 at 15:41 — Déjà vu, May 29 '13 at 15:41
At least under Ubuntu 13.04 it's `-F` or `--pidfile`. – velo9 May 30 '13 at 12:49 — velo9, May 30 '13 at 12:49

Devonte · Answer 1 · 2016-02-16T01:03:08.143

#!/bin/bash

# NGINX WATCH DAEMON
#
# Author: Devonte
#
# Place file in root of nginx folder: /etc/nginx
# This will test your nginx config on any change and
# if there are no problems it will reload your configuration
# USAGE: sh nginx-watch.sh

# Set NGINX directory
# tar command already has the leading /
dir='etc/nginx'

# Get initial checksum values
checksum_initial=$(tar --strip-components=2 -C / -cf - $dir | md5sum | awk '{print $1}')
checksum_now=$checksum_initial

# Start nginx
nginx

# Daemon that checks the md5 sum of the directory
# ff the sums are different ( a file changed / added / deleted)
# the nginx configuration is tested and reloaded on success
while true
do
    checksum_now=$(tar --strip-components=2 -C / -cf - $dir | md5sum | awk '{print $1}')

    if [ $checksum_initial != $checksum_now ]; then
        echo '[ NGINX ] A configuration file changed. Reloading...'
        nginx -t && nginx -s reload;
    fi

    checksum_initial=$checksum_now

    sleep 2
done

score 3 · Accepted Answer · edited May 23 '17 at 10:29

At least on Unix, both "reload" action and HUP signal are treated as one thanks to the declaration code

ngx_signal_t  signals[] = {
    { ngx_signal_value(NGX_RECONFIGURE_SIGNAL),
      "SIG" ngx_value(NGX_RECONFIGURE_SIGNAL),
      "reload",
      ngx_signal_handler },

in src/os/unix/ngx_process.c. In ngx_signal_handler() the same comnmon code

    case ngx_signal_value(NGX_RECONFIGURE_SIGNAL):
        ngx_reconfigure = 1;
        action = ", reconfiguring";
        break;

is executed, that prepares for a common reconfiguration.

To trigger an action when a file is modified, you could either make a crontab and decide of a check-periodicity, or use inotifywait.

To determine if nginx -t is in error, check the return code in a bash file, $?

nginx -t
if [ $? -eq 0 ] then;
    nginx -s reload
fi

Note: you may also use service nginx reload

(See return code check examples here)

There is a typo, it should be `nginx -t` instead of `linux -t` in the last code block. (can't change it because of silly "six characters needed for an edit" rule) — matlehmann, Jan 24 '14 at 16:52

How do you properly watch and reload Nginx conf?

2 Answers2