Environment: debian/ubuntu

This script can monitor cpu/memory usage of your node application, and start/stop it via a web interface or command line

Step 1. install startup and monit (they are normally preinstalled in ubuntu)

sudo apt-get install upstart monit

then edit /etc/defaults/monit, set startup=1

Step 2. in /etc/init/, create a config of your application, ex: your_app.conf with code

#!upstart

description "your_app"
author "Hongbo LU"

start on (local-filesystems and net-device-up IFACE=eth0)
stop on runlevel 0

respawn # restart when job dies
respawn limit 5 60 # give up restart after 5 respawns in 60 seconds

script  

exec start-stop-daemon --start --make-pidfile --pidfile /var/run/your_app.pid --chdir /path/to/your/app --chuid user:usergroup --exec NODE_ENV=production /usr/local/bin/node index.js >> /var/log/nodejs/node.log 2>&1

end script

NOTICE:

• user:usergroup must be the one who owns Node
• modify the log folder as you wish
• in order to use relative paths in Node, we must change directory to project’s folder

Step 3. edit file /etc/monit/monitrc, enable web interface

include /etc/monit/conf.d/*
set daemon 120 # Poll at 2-minute intervals
set logfile syslog facility log_daemon
set alert youremail@email.com
set httpd port 2812 and use address localhost
allow localhost   # Allow localhost to connect
allow admin:Monit # Allow Basic Auth

Step 4. create file /etc/monit/conf.d/your_app.monitrc

check process plusnode
    with pidfile "/var/run/your_app.pid"
    start program = "/sbin/start your_app"
    stop program = "/sbin/stop your_app"
    if 2 restarts within 3 cycles then timeout
    if totalmem > 100 Mb then alert
    if children > 255 for 5 cycles then stop
    if cpu usage > 95% for 3 cycles then restart
    if failed port 80 protocol http
	request /valid_url/
	with timeout 5 seconds
    and if failed port 443 type tcpssl protocol http
        request /valid_url/
        with timeout 5 seconds
	then restart

NOTICE:

• modify your_app as you wish
• modify server port as you wish
• monit will try to reach localhost:8080/valid_url to check the server status, so make sure your valid_url is valid

Step 5. now you can control your app. via web interface: localhost:2812 or via command:

#upstart command
sudo start your_app
sudo status your_app
sudo stop your_app
#the commands above are shortcuts of initctl:
initctl start your_app
initctl status your_app
#to check if the upstart conf is valid
initctl check-config
#to reload upstart configs
initctl reload-configuration
#monit command
sudo monit
sudo monit start your_app

NOTICE:

• if your app. stopped, monit will restart it automatically.