How do you properly watch and reload Nginx conf? - nginx

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?

Answer 1

#!/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

Answer 2

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)