Edit monit configuration file in /etc/monit/monitrc

monitrc

set daemon  120
set logfile syslog facility log_daemon

set mailserver smtp.gmail.com port 587 username "user@domain.com" password "userpassword" using tlsv1,
  with timeout 15 seconds

set eventqueue
    basedir /var/monit
    slots 1000

set mail-format { from: monit@mydomain.com }

set alert admin@domain.com

set httpd port 2812 and
   allow admin:monit

   check system localhost
      if loadavg (1min) > 3 then alert
      if loadavg (5min) > 2 then alert
      if memory usage > 60% then alert
      if cpu usage (user) > 70% then alert
      if cpu usage (system) > 30% then alert
      if cpu usage (wait) > 20% then alert

   ## nginx ##
   check process nginx with pidfile /opt/nginx/logs/nginx.pid
      start program = "/etc/init.d/nginx start"
      stop program  = "/etc/init.d/nginx stop"
      group server

   ## mysql ##
   check process mysql with pidfile /var/run/mysqld/mysqld.pid
      start program = "/etc/init.d/mysql start"
      stop program = "/etc/init.d/mysql stop"
      group database

   ## redis ##
   check process redis-server with pidfile /var/run/redis.pid
      start program = "/usr/bin/redis-server /etc/redis.conf"
      stop program = "/usr/bin/killall -9 redis-server"
      group redis